5 guestfs - Library for accessing and modifying virtual machine images
11 guestfs_h *g = guestfs_create ();
12 guestfs_add_drive (g, "guest.img");
14 guestfs_mount (g, "/dev/sda1", "/");
15 guestfs_touch (g, "/hello");
16 guestfs_umount (g, "/");
19 cc prog.c -o prog -lguestfs
21 cc prog.c -o prog `pkg-config libguestfs --cflags --libs`
25 Libguestfs is a library for accessing and modifying guest disk images.
26 Amongst the things this is good for: making batch configuration
27 changes to guests, getting disk used/free statistics (see also:
28 virt-df), migrating between virtualization systems (see also:
29 virt-p2v), performing partial backups, performing partial guest
30 clones, cloning guests and changing registry/UUID/hostname info, and
33 Libguestfs uses Linux kernel and qemu code, and can access any type of
34 guest filesystem that Linux and qemu can, including but not limited
35 to: ext2/3/4, btrfs, FAT and NTFS, LVM, many different disk partition
36 schemes, qcow, qcow2, vmdk.
38 Libguestfs provides ways to enumerate guest storage (eg. partitions,
39 LVs, what filesystem is in each LV, etc.). It can also run commands
40 in the context of the guest. Also you can access filesystems over
43 Libguestfs is a library that can be linked with C and C++ management
44 programs (or management programs written in OCaml, Perl, Python, Ruby,
45 Java, PHP, Erlang, Haskell or C#). You can also use it from shell
46 scripts or the command line.
48 You don't need to be root to use libguestfs, although obviously you do
49 need enough permissions to access the disk images.
51 Libguestfs is a large API because it can do many things. For a gentle
52 introduction, please read the L</API OVERVIEW> section next.
54 There are also some example programs in the L<guestfs-examples(3)>
59 This section provides a gentler overview of the libguestfs API. We
60 also try to group API calls together, where that may not be obvious
61 from reading about the individual calls in the main section of this
66 Before you can use libguestfs calls, you have to create a handle.
67 Then you must add at least one disk image to the handle, followed by
68 launching the handle, then performing whatever operations you want,
69 and finally closing the handle. By convention we use the single
70 letter C<g> for the name of the handle variable, although of course
71 you can use any name you want.
73 The general structure of all libguestfs-using programs looks like
76 guestfs_h *g = guestfs_create ();
78 /* Call guestfs_add_drive additional times if there are
79 * multiple disk images.
81 guestfs_add_drive (g, "guest.img");
83 /* Most manipulation calls won't work until you've launched
84 * the handle 'g'. You have to do this _after_ adding drives
85 * and _before_ other commands.
89 /* Now you can examine what partitions, LVs etc are available.
91 char **partitions = guestfs_list_partitions (g);
92 char **logvols = guestfs_lvs (g);
94 /* To access a filesystem in the image, you must mount it.
96 guestfs_mount (g, "/dev/sda1", "/");
98 /* Now you can perform filesystem actions on the guest
101 guestfs_touch (g, "/hello");
103 /* This is only needed for libguestfs < 1.5.24. Since then
104 * it is done automatically when you close the handle. See
105 * discussion of autosync in this page.
109 /* Close the handle 'g'. */
112 The code above doesn't include any error checking. In real code you
113 should check return values carefully for errors. In general all
114 functions that return integers return C<-1> on error, and all
115 functions that return pointers return C<NULL> on error. See section
116 L</ERROR HANDLING> below for how to handle errors, and consult the
117 documentation for each function call below to see precisely how they
118 return error indications. See L<guestfs-examples(3)> for fully worked
123 The image filename (C<"guest.img"> in the example above) could be a
124 disk image from a virtual machine, a L<dd(1)> copy of a physical hard
125 disk, an actual block device, or simply an empty file of zeroes that
126 you have created through L<posix_fallocate(3)>. Libguestfs lets you
127 do useful things to all of these.
129 The call you should use in modern code for adding drives is
130 L</guestfs_add_drive_opts>. To add a disk image, allowing writes, and
131 specifying that the format is raw, do:
133 guestfs_add_drive_opts (g, filename,
134 GUESTFS_ADD_DRIVE_OPTS_FORMAT, "raw",
137 You can add a disk read-only using:
139 guestfs_add_drive_opts (g, filename,
140 GUESTFS_ADD_DRIVE_OPTS_FORMAT, "raw",
141 GUESTFS_ADD_DRIVE_OPTS_READONLY, 1,
144 or by calling the older function L</guestfs_add_drive_ro>. In either
145 case libguestfs won't modify the file.
147 Be extremely cautious if the disk image is in use, eg. if it is being
148 used by a virtual machine. Adding it read-write will almost certainly
149 cause disk corruption, but adding it read-only is safe.
151 You must add at least one disk image, and you may add multiple disk
152 images. In the API, the disk images are usually referred to as
153 C</dev/sda> (for the first one you added), C</dev/sdb> (for the second
156 Once L</guestfs_launch> has been called you cannot add any more images.
157 You can call L</guestfs_list_devices> to get a list of the device
158 names, in the order that you added them. See also L</BLOCK DEVICE
163 Before you can read or write files, create directories and so on in a
164 disk image that contains filesystems, you have to mount those
165 filesystems using L</guestfs_mount_options> or L</guestfs_mount_ro>.
166 If you already know that a disk image contains (for example) one
167 partition with a filesystem on that partition, then you can mount it
170 guestfs_mount_options (g, "", "/dev/sda1", "/");
172 where C</dev/sda1> means literally the first partition (C<1>) of the
173 first disk image that we added (C</dev/sda>). If the disk contains
174 Linux LVM2 logical volumes you could refer to those instead
175 (eg. C</dev/VG/LV>). Note that these are libguestfs virtual devices,
176 and are nothing to do with host devices.
178 If you are given a disk image and you don't know what it contains then
179 you have to find out. Libguestfs can do that too: use
180 L</guestfs_list_partitions> and L</guestfs_lvs> to list possible
181 partitions and LVs, and either try mounting each to see what is
182 mountable, or else examine them with L</guestfs_vfs_type> or
183 L</guestfs_file>. To list just filesystems, use
184 L</guestfs_list_filesystems>.
186 Libguestfs also has a set of APIs for inspection of unknown disk
187 images (see L</INSPECTION> below). But you might find it easier to
188 look at higher level programs built on top of libguestfs, in
189 particular L<virt-inspector(1)>.
191 To mount a filesystem read-only, use L</guestfs_mount_ro>. There are
192 several other variations of the C<guestfs_mount_*> call.
194 =head2 FILESYSTEM ACCESS AND MODIFICATION
196 The majority of the libguestfs API consists of fairly low-level calls
197 for accessing and modifying the files, directories, symlinks etc on
198 mounted filesystems. There are over a hundred such calls which you
199 can find listed in detail below in this man page, and we don't even
200 pretend to cover them all in this overview.
202 Specify filenames as full paths, starting with C<"/"> and including
205 For example, if you mounted a filesystem at C<"/"> and you want to
206 read the file called C<"etc/passwd"> then you could do:
208 char *data = guestfs_cat (g, "/etc/passwd");
210 This would return C<data> as a newly allocated buffer containing the
211 full content of that file (with some conditions: see also
212 L</DOWNLOADING> below), or C<NULL> if there was an error.
214 As another example, to create a top-level directory on that filesystem
215 called C<"var"> you would do:
217 guestfs_mkdir (g, "/var");
219 To create a symlink you could do:
221 guestfs_ln_s (g, "/etc/init.d/portmap",
222 "/etc/rc3.d/S30portmap");
224 Libguestfs will reject attempts to use relative paths and there is no
225 concept of a current working directory.
227 Libguestfs can return errors in many situations: for example if the
228 filesystem isn't writable, or if a file or directory that you
229 requested doesn't exist. If you are using the C API (documented here)
230 you have to check for those error conditions after each call. (Other
231 language bindings turn these errors into exceptions).
233 File writes are affected by the per-handle umask, set by calling
234 L</guestfs_umask> and defaulting to 022. See L</UMASK>.
238 Libguestfs contains API calls to read, create and modify partition
239 tables on disk images.
241 In the common case where you want to create a single partition
242 covering the whole disk, you should use the L</guestfs_part_disk>
245 const char *parttype = "mbr";
246 if (disk_is_larger_than_2TB)
248 guestfs_part_disk (g, "/dev/sda", parttype);
250 Obviously this effectively wipes anything that was on that disk image
255 Libguestfs provides access to a large part of the LVM2 API, such as
256 L</guestfs_lvcreate> and L</guestfs_vgremove>. It won't make much sense
257 unless you familiarize yourself with the concepts of physical volumes,
258 volume groups and logical volumes.
260 This author strongly recommends reading the LVM HOWTO, online at
261 L<http://tldp.org/HOWTO/LVM-HOWTO/>.
265 Use L</guestfs_cat> to download small, text only files. This call is
266 limited to files which are less than 2 MB and which cannot contain any
267 ASCII NUL (C<\0>) characters. However the API is very simple to use.
269 L</guestfs_read_file> can be used to read files which contain
270 arbitrary 8 bit data, since it returns a (pointer, size) pair.
271 However it is still limited to "small" files, less than 2 MB.
273 L</guestfs_download> can be used to download any file, with no
274 limits on content or size (even files larger than 4 GB).
276 To download multiple files, see L</guestfs_tar_out> and
281 It's often the case that you want to write a file or files to the disk
284 To write a small file with fixed content, use L</guestfs_write>. To
285 create a file of all zeroes, use L</guestfs_truncate_size> (sparse) or
286 L</guestfs_fallocate64> (with all disk blocks allocated). There are a
287 variety of other functions for creating test files, for example
288 L</guestfs_fill> and L</guestfs_fill_pattern>.
290 To upload a single file, use L</guestfs_upload>. This call has no
291 limits on file content or size (even files larger than 4 GB).
293 To upload multiple files, see L</guestfs_tar_in> and L</guestfs_tgz_in>.
295 However the fastest way to upload I<large numbers of arbitrary files>
296 is to turn them into a squashfs or CD ISO (see L<mksquashfs(8)> and
297 L<mkisofs(8)>), then attach this using L</guestfs_add_drive_ro>. If
298 you add the drive in a predictable way (eg. adding it last after all
299 other drives) then you can get the device name from
300 L</guestfs_list_devices> and mount it directly using
301 L</guestfs_mount_ro>. Note that squashfs images are sometimes
302 non-portable between kernel versions, and they don't support labels or
303 UUIDs. If you want to pre-build an image or you need to mount it
304 using a label or UUID, use an ISO image instead.
308 There are various different commands for copying between files and
309 devices and in and out of the guest filesystem. These are summarised
314 =item B<file> to B<file>
316 Use L</guestfs_cp> to copy a single file, or
317 L</guestfs_cp_a> to copy directories recursively.
319 =item B<file or device> to B<file or device>
321 Use L</guestfs_dd> which efficiently uses L<dd(1)>
322 to copy between files and devices in the guest.
324 Example: duplicate the contents of an LV:
326 guestfs_dd (g, "/dev/VG/Original", "/dev/VG/Copy");
328 The destination (C</dev/VG/Copy>) must be at least as large as the
329 source (C</dev/VG/Original>). To copy less than the whole
330 source device, use L</guestfs_copy_size>.
332 =item B<file on the host> to B<file or device>
334 Use L</guestfs_upload>. See L</UPLOADING> above.
336 =item B<file or device> to B<file on the host>
338 Use L</guestfs_download>. See L</DOWNLOADING> above.
342 =head2 UPLOADING AND DOWNLOADING TO PIPES AND FILE DESCRIPTORS
344 Calls like L</guestfs_upload>, L</guestfs_download>,
345 L</guestfs_tar_in>, L</guestfs_tar_out> etc appear to only take
346 filenames as arguments, so it appears you can only upload and download
347 to files. However many Un*x-like hosts let you use the special device
348 files C</dev/stdin>, C</dev/stdout>, C</dev/stderr> and C</dev/fd/N>
349 to read and write from stdin, stdout, stderr, and arbitrary file
352 For example, L<virt-cat(1)> writes its output to stdout by
355 guestfs_download (g, filename, "/dev/stdout");
357 and you can write tar output to a file descriptor C<fd> by doing:
360 snprintf (devfd, sizeof devfd, "/dev/fd/%d", fd);
361 guestfs_tar_out (g, "/", devfd);
365 L</guestfs_ll> is just designed for humans to read (mainly when using
366 the L<guestfish(1)>-equivalent command C<ll>).
368 L</guestfs_ls> is a quick way to get a list of files in a directory
369 from programs, as a flat list of strings.
371 L</guestfs_readdir> is a programmatic way to get a list of files in a
372 directory, plus additional information about each one. It is more
373 equivalent to using the L<readdir(3)> call on a local filesystem.
375 L</guestfs_find> and L</guestfs_find0> can be used to recursively list
378 =head2 RUNNING COMMANDS
380 Although libguestfs is primarily an API for manipulating files
381 inside guest images, we also provide some limited facilities for
382 running commands inside guests.
384 There are many limitations to this:
390 The kernel version that the command runs under will be different
391 from what it expects.
395 If the command needs to communicate with daemons, then most likely
396 they won't be running.
400 The command will be running in limited memory.
404 The network may not be available unless you enable it
405 (see L</guestfs_set_network>).
409 Only supports Linux guests (not Windows, BSD, etc).
413 Architecture limitations (eg. won't work for a PPC guest on
418 For SELinux guests, you may need to enable SELinux and load policy
419 first. See L</SELINUX> in this manpage.
423 I<Security:> It is not safe to run commands from untrusted, possibly
424 malicious guests. These commands may attempt to exploit your program
425 by sending unexpected output. They could also try to exploit the
426 Linux kernel or qemu provided by the libguestfs appliance. They could
427 use the network provided by the libguestfs appliance to bypass
428 ordinary network partitions and firewalls. They could use the
429 elevated privileges or different SELinux context of your program
432 A secure alternative is to use libguestfs to install a "firstboot"
433 script (a script which runs when the guest next boots normally), and
434 to have this script run the commands you want in the normal context of
435 the running guest, network security and so on. For information about
436 other security issues, see L</SECURITY>.
440 The two main API calls to run commands are L</guestfs_command> and
441 L</guestfs_sh> (there are also variations).
443 The difference is that L</guestfs_sh> runs commands using the shell, so
444 any shell globs, redirections, etc will work.
446 =head2 CONFIGURATION FILES
448 To read and write configuration files in Linux guest filesystems, we
449 strongly recommend using Augeas. For example, Augeas understands how
450 to read and write, say, a Linux shadow password file or X.org
451 configuration file, and so avoids you having to write that code.
453 The main Augeas calls are bound through the C<guestfs_aug_*> APIs. We
454 don't document Augeas itself here because there is excellent
455 documentation on the L<http://augeas.net/> website.
457 If you don't want to use Augeas (you fool!) then try calling
458 L</guestfs_read_lines> to get the file as a list of lines which
459 you can iterate over.
463 We support SELinux guests. To ensure that labeling happens correctly
464 in SELinux guests, you need to enable SELinux and load the guest's
471 Before launching, do:
473 guestfs_set_selinux (g, 1);
477 After mounting the guest's filesystem(s), load the policy. This
478 is best done by running the L<load_policy(8)> command in the
481 guestfs_sh (g, "/usr/sbin/load_policy");
483 (Older versions of C<load_policy> require you to specify the
484 name of the policy file).
488 Optionally, set the security context for the API. The correct
489 security context to use can only be known by inspecting the
490 guest. As an example:
492 guestfs_setcon (g, "unconfined_u:unconfined_r:unconfined_t:s0");
496 This will work for running commands and editing existing files.
498 When new files are created, you may need to label them explicitly,
499 for example by running the external command
500 C<restorecon pathname>.
504 Certain calls are affected by the current file mode creation mask (the
505 "umask"). In particular ones which create files or directories, such
506 as L</guestfs_touch>, L</guestfs_mknod> or L</guestfs_mkdir>. This
507 affects either the default mode that the file is created with or
508 modifies the mode that you supply.
510 The default umask is C<022>, so files are created with modes such as
511 C<0644> and directories with C<0755>.
513 There are two ways to avoid being affected by umask. Either set umask
514 to 0 (call C<guestfs_umask (g, 0)> early after launching). Or call
515 L</guestfs_chmod> after creating each file or directory.
517 For more information about umask, see L<umask(2)>.
519 =head2 ENCRYPTED DISKS
521 Libguestfs allows you to access Linux guests which have been
522 encrypted using whole disk encryption that conforms to the
523 Linux Unified Key Setup (LUKS) standard. This includes
524 nearly all whole disk encryption systems used by modern
527 Use L</guestfs_vfs_type> to identify LUKS-encrypted block
528 devices (it returns the string C<crypto_LUKS>).
530 Then open these devices by calling L</guestfs_luks_open>.
531 Obviously you will require the passphrase!
533 Opening a LUKS device creates a new device mapper device
534 called C</dev/mapper/mapname> (where C<mapname> is the
535 string you supply to L</guestfs_luks_open>).
536 Reads and writes to this mapper device are decrypted from and
537 encrypted to the underlying block device respectively.
539 LVM volume groups on the device can be made visible by calling
540 L</guestfs_vgscan> followed by L</guestfs_vg_activate_all>.
541 The logical volume(s) can now be mounted in the usual way.
543 Use the reverse process to close a LUKS device. Unmount
544 any logical volumes on it, deactivate the volume groups
545 by caling C<guestfs_vg_activate (g, 0, ["/dev/VG"])>.
546 Then close the mapper device by calling
547 L</guestfs_luks_close> on the C</dev/mapper/mapname>
548 device (I<not> the underlying encrypted block device).
552 Libguestfs has APIs for inspecting an unknown disk image to find out
553 if it contains operating systems, an install CD or a live CD. (These
554 APIs used to be in a separate Perl-only library called
555 L<Sys::Guestfs::Lib(3)> but since version 1.5.3 the most frequently
556 used part of this library has been rewritten in C and moved into the
559 Add all disks belonging to the unknown virtual machine and call
560 L</guestfs_launch> in the usual way.
562 Then call L</guestfs_inspect_os>. This function uses other libguestfs
563 calls and certain heuristics, and returns a list of operating systems
564 that were found. An empty list means none were found. A single
565 element is the root filesystem of the operating system. For dual- or
566 multi-boot guests, multiple roots can be returned, each one
567 corresponding to a separate operating system. (Multi-boot virtual
568 machines are extremely rare in the world of virtualization, but since
569 this scenario can happen, we have built libguestfs to deal with it.)
571 For each root, you can then call various C<guestfs_inspect_get_*>
572 functions to get additional details about that operating system. For
573 example, call L</guestfs_inspect_get_type> to return the string
574 C<windows> or C<linux> for Windows and Linux-based operating systems
577 Un*x-like and Linux-based operating systems usually consist of several
578 filesystems which are mounted at boot time (for example, a separate
579 boot partition mounted on C</boot>). The inspection rules are able to
580 detect how filesystems correspond to mount points. Call
581 C<guestfs_inspect_get_mountpoints> to get this mapping. It might
582 return a hash table like this example:
585 / => /dev/vg_guest/lv_root
586 /usr => /dev/vg_guest/lv_usr
588 The caller can then make calls to L</guestfs_mount_options> to
589 mount the filesystems as suggested.
591 Be careful to mount filesystems in the right order (eg. C</> before
592 C</usr>). Sorting the keys of the hash by length, shortest first,
595 Inspection currently only works for some common operating systems.
596 Contributors are welcome to send patches for other operating systems
597 that we currently cannot detect.
599 Encrypted disks must be opened before inspection. See
600 L</ENCRYPTED DISKS> for more details. The L</guestfs_inspect_os>
601 function just ignores any encrypted devices.
603 A note on the implementation: The call L</guestfs_inspect_os> performs
604 inspection and caches the results in the guest handle. Subsequent
605 calls to C<guestfs_inspect_get_*> return this cached information, but
606 I<do not> re-read the disks. If you change the content of the guest
607 disks, you can redo inspection by calling L</guestfs_inspect_os>
608 again. (L</guestfs_inspect_list_applications> works a little
609 differently from the other calls and does read the disks. See
610 documentation for that function for details).
612 =head3 INSPECTING INSTALL DISKS
614 Libguestfs (since 1.9.4) can detect some install disks, install
615 CDs, live CDs and more.
617 Call L</guestfs_inspect_get_format> to return the format of the
618 operating system, which currently can be C<installed> (a regular
619 operating system) or C<installer> (some sort of install disk).
621 Further information is available about the operating system that can
622 be installed using the regular inspection APIs like
623 L</guestfs_inspect_get_product_name>,
624 L</guestfs_inspect_get_major_version> etc.
626 Some additional information specific to installer disks is also
627 available from the L</guestfs_inspect_is_live>,
628 L</guestfs_inspect_is_netinst> and L</guestfs_inspect_is_multipart>
631 =head2 SPECIAL CONSIDERATIONS FOR WINDOWS GUESTS
633 Libguestfs can mount NTFS partitions. It does this using the
634 L<http://www.ntfs-3g.org/> driver.
636 =head3 DRIVE LETTERS AND PATHS
638 DOS and Windows still use drive letters, and the filesystems are
639 always treated as case insensitive by Windows itself, and therefore
640 you might find a Windows configuration file referring to a path like
641 C<c:\windows\system32>. When the filesystem is mounted in libguestfs,
642 that directory might be referred to as C</WINDOWS/System32>.
644 Drive letter mappings can be found using inspection
645 (see L</INSPECTION> and L</guestfs_inspect_get_drive_mappings>)
647 Dealing with separator characters (backslash vs forward slash) is
648 outside the scope of libguestfs, but usually a simple character
649 replacement will work.
651 To resolve the case insensitivity of paths, call
652 L</guestfs_case_sensitive_path>.
654 =head3 ACCESSING THE WINDOWS REGISTRY
656 Libguestfs also provides some help for decoding Windows Registry
657 "hive" files, through the library C<hivex> which is part of the
658 libguestfs project although ships as a separate tarball. You have to
659 locate and download the hive file(s) yourself, and then pass them to
660 C<hivex> functions. See also the programs L<hivexml(1)>,
661 L<hivexsh(1)>, L<hivexregedit(1)> and L<virt-win-reg(1)> for more help
664 =head3 SYMLINKS ON NTFS-3G FILESYSTEMS
666 Ntfs-3g tries to rewrite "Junction Points" and NTFS "symbolic links"
667 to provide something which looks like a Linux symlink. The way it
668 tries to do the rewriting is described here:
670 L<http://www.tuxera.com/community/ntfs-3g-advanced/junction-points-and-symbolic-links/>
672 The essential problem is that ntfs-3g simply does not have enough
673 information to do a correct job. NTFS links can contain drive letters
674 and references to external device GUIDs that ntfs-3g has no way of
675 resolving. It is almost certainly the case that libguestfs callers
676 should ignore what ntfs-3g does (ie. don't use L</guestfs_readlink> on
679 Instead if you encounter a symbolic link on an ntfs-3g filesystem, use
680 L</guestfs_lgetxattr> to read the C<system.ntfs_reparse_data> extended
681 attribute, and read the raw reparse data from that (you can find the
682 format documented in various places around the web).
684 =head3 EXTENDED ATTRIBUTES ON NTFS-3G FILESYSTEMS
686 There are other useful extended attributes that can be read from
687 ntfs-3g filesystems (using L</guestfs_getxattr>). See:
689 L<http://www.tuxera.com/community/ntfs-3g-advanced/extended-attributes/>
691 =head2 USING LIBGUESTFS WITH OTHER PROGRAMMING LANGUAGES
693 Although we don't want to discourage you from using the C API, we will
694 mention here that the same API is also available in other languages.
696 The API is broadly identical in all supported languages. This means
697 that the C call C<guestfs_add_drive_ro(g,file)> is
698 C<$g-E<gt>add_drive_ro($file)> in Perl, C<g.add_drive_ro(file)> in Python,
699 and C<g#add_drive_ro file> in OCaml. In other words, a
700 straightforward, predictable isomorphism between each language.
702 Error messages are automatically transformed
703 into exceptions if the language supports it.
705 We don't try to "object orientify" parts of the API in OO languages,
706 although contributors are welcome to write higher level APIs above
707 what we provide in their favourite languages if they wish.
713 You can use the I<guestfs.h> header file from C++ programs. The C++
714 API is identical to the C API. C++ classes and exceptions are not
719 The C# bindings are highly experimental. Please read the warnings
720 at the top of C<csharp/Libguestfs.cs>.
724 See L<guestfs-erlang(3)>.
728 This is the only language binding that is working but incomplete.
729 Only calls which return simple integers have been bound in Haskell,
730 and we are looking for help to complete this binding.
734 Full documentation is contained in the Javadoc which is distributed
735 with libguestfs. For examples, see L<guestfs-java(3)>.
739 See L<guestfs-ocaml(3)>.
743 See L<guestfs-perl(3)> and L<Sys::Guestfs(3)>.
747 For documentation see C<README-PHP> supplied with libguestfs
748 sources or in the php-libguestfs package for your distribution.
750 The PHP binding only works correctly on 64 bit machines.
754 See L<guestfs-python(3)>.
758 See L<guestfs-ruby(3)>.
760 =item B<shell scripts>
766 =head2 LIBGUESTFS GOTCHAS
768 L<http://en.wikipedia.org/wiki/Gotcha_(programming)>: "A feature of a
769 system [...] that works in the way it is documented but is
770 counterintuitive and almost invites mistakes."
772 Since we developed libguestfs and the associated tools, there are
773 several things we would have designed differently, but are now stuck
774 with for backwards compatibility or other reasons. If there is ever a
775 libguestfs 2.0 release, you can expect these to change. Beware of
780 =item Autosync / forgetting to sync.
782 I<Update:> Autosync is enabled by default for all API users starting
783 from libguestfs 1.5.24. This section only applies to older versions.
785 When modifying a filesystem from C or another language, you B<must>
786 unmount all filesystems and call L</guestfs_sync> explicitly before
787 you close the libguestfs handle. You can also call:
789 guestfs_set_autosync (g, 1);
791 to have the unmount/sync done automatically for you when the handle 'g'
792 is closed. (This feature is called "autosync", L</guestfs_set_autosync>
795 If you forget to do this, then it is entirely possible that your
796 changes won't be written out, or will be partially written, or (very
797 rarely) that you'll get disk corruption.
799 Note that in L<guestfish(3)> autosync is the default. So quick and
800 dirty guestfish scripts that forget to sync will work just fine, which
801 can make this very puzzling if you are trying to debug a problem.
803 =item Mount option C<-o sync> should not be the default.
805 If you use L</guestfs_mount>, then C<-o sync,noatime> are added
806 implicitly. However C<-o sync> does not add any reliability benefit,
807 but does have a very large performance impact.
809 The work around is to use L</guestfs_mount_options> and set the mount
810 options that you actually want to use.
812 =item Read-only should be the default.
814 In L<guestfish(3)>, I<--ro> should be the default, and you should
815 have to specify I<--rw> if you want to make changes to the image.
817 This would reduce the potential to corrupt live VM images.
819 Note that many filesystems change the disk when you just mount and
820 unmount, even if you didn't perform any writes. You need to use
821 L</guestfs_add_drive_ro> to guarantee that the disk is not changed.
823 =item guestfish command line is hard to use.
825 C<guestfish disk.img> doesn't do what people expect (open C<disk.img>
826 for examination). It tries to run a guestfish command C<disk.img>
827 which doesn't exist, so it fails. In earlier versions of guestfish
828 the error message was also unintuitive, but we have corrected this
829 since. Like the Bourne shell, we should have used C<guestfish -c
830 command> to run commands.
832 =item guestfish megabyte modifiers don't work right on all commands
834 In recent guestfish you can use C<1M> to mean 1 megabyte (and
835 similarly for other modifiers). What guestfish actually does is to
836 multiply the number part by the modifier part and pass the result to
837 the C API. However this doesn't work for a few APIs which aren't
838 expecting bytes, but are already expecting some other unit
841 The most common is L</guestfs_lvcreate>. The guestfish command:
845 does not do what you might expect. Instead because
846 L</guestfs_lvcreate> is already expecting megabytes, this tries to
847 create a 100 I<terabyte> (100 megabytes * megabytes) logical volume.
848 The error message you get from this is also a little obscure.
850 This could be fixed in the generator by specially marking parameters
851 and return values which take bytes or other units.
853 =item Ambiguity between devices and paths
855 There is a subtle ambiguity in the API between a device name
856 (eg. C</dev/sdb2>) and a similar pathname. A file might just happen
857 to be called C<sdb2> in the directory C</dev> (consider some non-Unix
860 In the current API we usually resolve this ambiguity by having two
861 separate calls, for example L</guestfs_checksum> and
862 L</guestfs_checksum_device>. Some API calls are ambiguous and
863 (incorrectly) resolve the problem by detecting if the path supplied
864 begins with C</dev/>.
866 To avoid both the ambiguity and the need to duplicate some calls, we
867 could make paths/devices into structured names. One way to do this
868 would be to use a notation like grub (C<hd(0,0)>), although nobody
869 really likes this aspect of grub. Another way would be to use a
870 structured type, equivalent to this OCaml type:
872 type path = Path of string | Device of int | Partition of int * int
874 which would allow you to pass arguments like:
877 Device 1 (* /dev/sdb, or perhaps /dev/sda *)
878 Partition (1, 2) (* /dev/sdb2 (or is it /dev/sda2 or /dev/sdb3?) *)
879 Path "/dev/sdb2" (* not a device *)
881 As you can see there are still problems to resolve even with this
882 representation. Also consider how it might work in guestfish.
886 =head2 KEYS AND PASSPHRASES
888 Certain libguestfs calls take a parameter that contains sensitive key
889 material, passed in as a C string.
891 In the future we would hope to change the libguestfs implementation so
892 that keys are L<mlock(2)>-ed into physical RAM, and thus can never end
893 up in swap. However this is I<not> done at the moment, because of the
894 complexity of such an implementation.
896 Therefore you should be aware that any key parameter you pass to
897 libguestfs might end up being written out to the swap partition. If
898 this is a concern, scrub the swap partition or don't use libguestfs on
901 =head2 MULTIPLE HANDLES AND MULTIPLE THREADS
903 All high-level libguestfs actions are synchronous. If you want
904 to use libguestfs asynchronously then you must create a thread.
906 Only use the handle from a single thread. Either use the handle
907 exclusively from one thread, or provide your own mutex so that two
908 threads cannot issue calls on the same handle at the same time.
910 See the graphical program guestfs-browser for one possible
911 architecture for multithreaded programs using libvirt and libguestfs.
915 Libguestfs needs a supermin appliance, which it finds by looking along
918 By default it looks for these in the directory C<$libdir/guestfs>
919 (eg. C</usr/local/lib/guestfs> or C</usr/lib64/guestfs>).
921 Use L</guestfs_set_path> or set the environment variable
922 L</LIBGUESTFS_PATH> to change the directories that libguestfs will
923 search in. The value is a colon-separated list of paths. The current
924 directory is I<not> searched unless the path contains an empty element
925 or C<.>. For example C<LIBGUESTFS_PATH=:/usr/lib/guestfs> would
926 search the current directory and then C</usr/lib/guestfs>.
930 If you want to compile your own qemu, run qemu from a non-standard
931 location, or pass extra arguments to qemu, then you can write a
932 shell-script wrapper around qemu.
934 There is one important rule to remember: you I<must C<exec qemu>> as
935 the last command in the shell script (so that qemu replaces the shell
936 and becomes the direct child of the libguestfs-using program). If you
937 don't do this, then the qemu process won't be cleaned up correctly.
939 Here is an example of a wrapper, where I have built my own copy of
943 qemudir=/home/rjones/d/qemu
944 exec $qemudir/x86_64-softmmu/qemu-system-x86_64 -L $qemudir/pc-bios "$@"
946 Save this script as C</tmp/qemu.wrapper> (or wherever), C<chmod +x>,
947 and then use it by setting the LIBGUESTFS_QEMU environment variable.
950 LIBGUESTFS_QEMU=/tmp/qemu.wrapper guestfish
952 Note that libguestfs also calls qemu with the -help and -version
953 options in order to determine features.
955 Wrappers can also be used to edit the options passed to qemu. In the
956 following example, the C<-machine ...> option (C<-machine> and the
957 following argument) are removed from the command line and replaced
958 with C<-machine pc,accel=tcg>. The while loop iterates over the
959 options until it finds the right one to remove, putting the remaining
960 options into the C<args> array.
965 while [ $# -gt 0 ]; do
976 exec qemu-kvm -machine pc,accel=tcg "${args[@]}"
978 =head2 ATTACHING TO RUNNING DAEMONS
980 I<Note (1):> This is B<highly experimental> and has a tendency to eat
981 babies. Use with caution.
983 I<Note (2):> This section explains how to attach to a running daemon
984 from a low level perspective. For most users, simply using virt tools
985 such as L<guestfish(1)> with the I<--live> option will "just work".
987 =head3 Using guestfs_set_attach_method
989 By calling L</guestfs_set_attach_method> you can change how the
990 library connects to the C<guestfsd> daemon in L</guestfs_launch>
991 (read L</ARCHITECTURE> for some background).
993 The normal attach method is C<appliance>, where a small appliance is
994 created containing the daemon, and then the library connects to this.
996 Setting attach method to C<unix:I<path>> (where I<path> is the path of
997 a Unix domain socket) causes L</guestfs_launch> to connect to an
998 existing daemon over the Unix domain socket.
1000 The normal use for this is to connect to a running virtual machine
1001 that contains a C<guestfsd> daemon, and send commands so you can read
1002 and write files inside the live virtual machine.
1004 =head3 Using guestfs_add_domain with live flag
1006 L</guestfs_add_domain> provides some help for getting the
1007 correct attach method. If you pass the C<live> option to this
1008 function, then (if the virtual machine is running) it will
1009 examine the libvirt XML looking for a virtio-serial channel
1016 <channel type='unix'>
1017 <source mode='bind' path='/path/to/socket'/>
1018 <target type='virtio' name='org.libguestfs.channel.0'/>
1024 L</guestfs_add_domain> extracts C</path/to/socket> and sets the attach
1025 method to C<unix:/path/to/socket>.
1027 Some of the libguestfs tools (including guestfish) support a I<--live>
1028 option which is passed through to L</guestfs_add_domain> thus allowing
1029 you to attach to and modify live virtual machines.
1031 The virtual machine needs to have been set up beforehand so that it
1032 has the virtio-serial channel and so that guestfsd is running inside
1035 =head2 ABI GUARANTEE
1037 We guarantee the libguestfs ABI (binary interface), for public,
1038 high-level actions as outlined in this section. Although we will
1039 deprecate some actions, for example if they get replaced by newer
1040 calls, we will keep the old actions forever. This allows you the
1041 developer to program in confidence against the libguestfs API.
1043 =head2 BLOCK DEVICE NAMING
1045 In the kernel there is now quite a profusion of schemata for naming
1046 block devices (in this context, by I<block device> I mean a physical
1047 or virtual hard drive). The original Linux IDE driver used names
1048 starting with C</dev/hd*>. SCSI devices have historically used a
1049 different naming scheme, C</dev/sd*>. When the Linux kernel I<libata>
1050 driver became a popular replacement for the old IDE driver
1051 (particularly for SATA devices) those devices also used the
1052 C</dev/sd*> scheme. Additionally we now have virtual machines with
1053 paravirtualized drivers. This has created several different naming
1054 systems, such as C</dev/vd*> for virtio disks and C</dev/xvd*> for Xen
1057 As discussed above, libguestfs uses a qemu appliance running an
1058 embedded Linux kernel to access block devices. We can run a variety
1059 of appliances based on a variety of Linux kernels.
1061 This causes a problem for libguestfs because many API calls use device
1062 or partition names. Working scripts and the recipe (example) scripts
1063 that we make available over the internet could fail if the naming
1066 Therefore libguestfs defines C</dev/sd*> as the I<standard naming
1067 scheme>. Internally C</dev/sd*> names are translated, if necessary,
1068 to other names as required. For example, under RHEL 5 which uses the
1069 C</dev/hd*> scheme, any device parameter C</dev/sda2> is translated to
1070 C</dev/hda2> transparently.
1072 Note that this I<only> applies to parameters. The
1073 L</guestfs_list_devices>, L</guestfs_list_partitions> and similar calls
1074 return the true names of the devices and partitions as known to the
1077 =head3 ALGORITHM FOR BLOCK DEVICE NAME TRANSLATION
1079 Usually this translation is transparent. However in some (very rare)
1080 cases you may need to know the exact algorithm. Such cases include
1081 where you use L</guestfs_config> to add a mixture of virtio and IDE
1082 devices to the qemu-based appliance, so have a mixture of C</dev/sd*>
1083 and C</dev/vd*> devices.
1085 The algorithm is applied only to I<parameters> which are known to be
1086 either device or partition names. Return values from functions such
1087 as L</guestfs_list_devices> are never changed.
1093 Is the string a parameter which is a device or partition name?
1097 Does the string begin with C</dev/sd>?
1101 Does the named device exist? If so, we use that device.
1102 However if I<not> then we continue with this algorithm.
1106 Replace initial C</dev/sd> string with C</dev/hd>.
1108 For example, change C</dev/sda2> to C</dev/hda2>.
1110 If that named device exists, use it. If not, continue.
1114 Replace initial C</dev/sd> string with C</dev/vd>.
1116 If that named device exists, use it. If not, return an error.
1120 =head3 PORTABILITY CONCERNS WITH BLOCK DEVICE NAMING
1122 Although the standard naming scheme and automatic translation is
1123 useful for simple programs and guestfish scripts, for larger programs
1124 it is best not to rely on this mechanism.
1126 Where possible for maximum future portability programs using
1127 libguestfs should use these future-proof techniques:
1133 Use L</guestfs_list_devices> or L</guestfs_list_partitions> to list
1134 actual device names, and then use those names directly.
1136 Since those device names exist by definition, they will never be
1141 Use higher level ways to identify filesystems, such as LVM names,
1142 UUIDs and filesystem labels.
1148 This section discusses security implications of using libguestfs,
1149 particularly with untrusted or malicious guests or disk images.
1151 =head2 GENERAL SECURITY CONSIDERATIONS
1153 Be careful with any files or data that you download from a guest (by
1154 "download" we mean not just the L</guestfs_download> command but any
1155 command that reads files, filenames, directories or anything else from
1156 a disk image). An attacker could manipulate the data to fool your
1157 program into doing the wrong thing. Consider cases such as:
1163 the data (file etc) not being present
1167 being present but empty
1171 being much larger than normal
1175 containing arbitrary 8 bit data
1179 being in an unexpected character encoding
1183 containing homoglyphs.
1187 =head2 SECURITY OF MOUNTING FILESYSTEMS
1189 When you mount a filesystem under Linux, mistakes in the kernel
1190 filesystem (VFS) module can sometimes be escalated into exploits by
1191 deliberately creating a malicious, malformed filesystem. These
1192 exploits are very severe for two reasons. Firstly there are very many
1193 filesystem drivers in the kernel, and many of them are infrequently
1194 used and not much developer attention has been paid to the code.
1195 Linux userspace helps potential crackers by detecting the filesystem
1196 type and automatically choosing the right VFS driver, even if that
1197 filesystem type is obscure or unexpected for the administrator.
1198 Secondly, a kernel-level exploit is like a local root exploit (worse
1199 in some ways), giving immediate and total access to the system right
1200 down to the hardware level.
1202 That explains why you should never mount a filesystem from an
1203 untrusted guest on your host kernel. How about libguestfs? We run a
1204 Linux kernel inside a qemu virtual machine, usually running as a
1205 non-root user. The attacker would need to write a filesystem which
1206 first exploited the kernel, and then exploited either qemu
1207 virtualization (eg. a faulty qemu driver) or the libguestfs protocol,
1208 and finally to be as serious as the host kernel exploit it would need
1209 to escalate its privileges to root. This multi-step escalation,
1210 performed by a static piece of data, is thought to be extremely hard
1211 to do, although we never say 'never' about security issues.
1213 In any case callers can reduce the attack surface by forcing the
1214 filesystem type when mounting (use L</guestfs_mount_vfs>).
1216 =head2 PROTOCOL SECURITY
1218 The protocol is designed to be secure, being based on RFC 4506 (XDR)
1219 with a defined upper message size. However a program that uses
1220 libguestfs must also take care - for example you can write a program
1221 that downloads a binary from a disk image and executes it locally, and
1222 no amount of protocol security will save you from the consequences.
1224 =head2 INSPECTION SECURITY
1226 Parts of the inspection API (see L</INSPECTION>) return untrusted
1227 strings directly from the guest, and these could contain any 8 bit
1228 data. Callers should be careful to escape these before printing them
1229 to a structured file (for example, use HTML escaping if creating a web
1232 Guest configuration may be altered in unusual ways by the
1233 administrator of the virtual machine, and may not reflect reality
1234 (particularly for untrusted or actively malicious guests). For
1235 example we parse the hostname from configuration files like
1236 C</etc/sysconfig/network> that we find in the guest, but the guest
1237 administrator can easily manipulate these files to provide the wrong
1240 The inspection API parses guest configuration using two external
1241 libraries: Augeas (Linux configuration) and hivex (Windows Registry).
1242 Both are designed to be robust in the face of malicious data, although
1243 denial of service attacks are still possible, for example with
1244 oversized configuration files.
1246 =head2 RUNNING UNTRUSTED GUEST COMMANDS
1248 Be very cautious about running commands from the guest. By running a
1249 command in the guest, you are giving CPU time to a binary that you do
1250 not control, under the same user account as the library, albeit
1251 wrapped in qemu virtualization. More information and alternatives can
1252 be found in the section L</RUNNING COMMANDS>.
1254 =head2 CVE-2010-3851
1256 https://bugzilla.redhat.com/642934
1258 This security bug concerns the automatic disk format detection that
1259 qemu does on disk images.
1261 A raw disk image is just the raw bytes, there is no header. Other
1262 disk images like qcow2 contain a special header. Qemu deals with this
1263 by looking for one of the known headers, and if none is found then
1264 assuming the disk image must be raw.
1266 This allows a guest which has been given a raw disk image to write
1267 some other header. At next boot (or when the disk image is accessed
1268 by libguestfs) qemu would do autodetection and think the disk image
1269 format was, say, qcow2 based on the header written by the guest.
1271 This in itself would not be a problem, but qcow2 offers many features,
1272 one of which is to allow a disk image to refer to another image
1273 (called the "backing disk"). It does this by placing the path to the
1274 backing disk into the qcow2 header. This path is not validated and
1275 could point to any host file (eg. "/etc/passwd"). The backing disk is
1276 then exposed through "holes" in the qcow2 disk image, which of course
1277 is completely under the control of the attacker.
1279 In libguestfs this is rather hard to exploit except under two
1286 You have enabled the network or have opened the disk in write mode.
1290 You are also running untrusted code from the guest (see
1291 L</RUNNING COMMANDS>).
1295 The way to avoid this is to specify the expected disk format when
1296 adding disks (the optional C<format> option to
1297 L</guestfs_add_drive_opts>). You should always do this if the disk is
1298 raw format, and it's a good idea for other cases too.
1300 For disks added from libvirt using calls like L</guestfs_add_domain>,
1301 the format is fetched from libvirt and passed through.
1303 For libguestfs tools, use the I<--format> command line parameter as
1306 =head1 CONNECTION MANAGEMENT
1310 C<guestfs_h> is the opaque type representing a connection handle.
1311 Create a handle by calling L</guestfs_create>. Call L</guestfs_close>
1312 to free the handle and release all resources used.
1314 For information on using multiple handles and threads, see the section
1315 L</MULTIPLE HANDLES AND MULTIPLE THREADS> above.
1317 =head2 guestfs_create
1319 guestfs_h *guestfs_create (void);
1321 Create a connection handle.
1323 On success this returns a non-NULL pointer to a handle. On error it
1326 You have to "configure" the handle after creating it. This includes
1327 calling L</guestfs_add_drive_opts> (or one of the equivalent calls) on
1328 the handle at least once.
1330 After configuring the handle, you have to call L</guestfs_launch>.
1332 You may also want to configure error handling for the handle. See the
1333 L</ERROR HANDLING> section below.
1335 =head2 guestfs_close
1337 void guestfs_close (guestfs_h *g);
1339 This closes the connection handle and frees up all resources used.
1341 If autosync was set on the handle and the handle was launched, then
1342 this implicitly calls various functions to unmount filesystems and
1343 sync the disk. See L</guestfs_set_autosync> for more details.
1345 If a close callback was set on the handle, then it is called.
1347 =head1 ERROR HANDLING
1349 API functions can return errors. For example, almost all functions
1350 that return C<int> will return C<-1> to indicate an error.
1352 Additional information is available for errors: an error message
1353 string and optionally an error number (errno) if the thing that failed
1356 You can get at the additional information about the last error on the
1357 handle by calling L</guestfs_last_error>, L</guestfs_last_errno>,
1358 and/or by setting up an error handler with
1359 L</guestfs_set_error_handler>.
1361 When the handle is created, a default error handler is installed which
1362 prints the error message string to C<stderr>. For small short-running
1363 command line programs it is sufficient to do:
1365 if (guestfs_launch (g) == -1)
1366 exit (EXIT_FAILURE);
1368 since the default error handler will ensure that an error message has
1369 been printed to C<stderr> before the program exits.
1371 For other programs the caller will almost certainly want to install an
1372 alternate error handler or do error handling in-line like this:
1374 /* This disables the default behaviour of printing errors
1376 guestfs_set_error_handler (g, NULL, NULL);
1378 if (guestfs_launch (g) == -1) {
1379 /* Examine the error message and print it etc. */
1380 char *msg = guestfs_last_error (g);
1381 int errnum = guestfs_last_errno (g);
1382 fprintf (stderr, "%s", msg);
1384 fprintf (stderr, ": %s", strerror (errnum));
1385 fprintf (stderr, "\n");
1389 Out of memory errors are handled differently. The default action is
1390 to call L<abort(3)>. If this is undesirable, then you can set a
1391 handler using L</guestfs_set_out_of_memory_handler>.
1393 L</guestfs_create> returns C<NULL> if the handle cannot be created,
1394 and because there is no handle if this happens there is no way to get
1395 additional error information. However L</guestfs_create> is supposed
1396 to be a lightweight operation which can only fail because of
1397 insufficient memory (it returns NULL in this case).
1399 =head2 guestfs_last_error
1401 const char *guestfs_last_error (guestfs_h *g);
1403 This returns the last error message that happened on C<g>. If
1404 there has not been an error since the handle was created, then this
1407 The lifetime of the returned string is until the next error occurs, or
1408 L</guestfs_close> is called.
1410 =head2 guestfs_last_errno
1412 int guestfs_last_errno (guestfs_h *g);
1414 This returns the last error number (errno) that happened on C<g>.
1416 If successful, an errno integer not equal to zero is returned.
1418 If no error, this returns 0. This call can return 0 in three
1425 There has not been any error on the handle.
1429 There has been an error but the errno was meaningless. This
1430 corresponds to the case where the error did not come from a
1431 failed system call, but for some other reason.
1435 There was an error from a failed system call, but for some
1436 reason the errno was not captured and returned. This usually
1437 indicates a bug in libguestfs.
1441 Libguestfs tries to convert the errno from inside the applicance into
1442 a corresponding errno for the caller (not entirely trivial: the
1443 appliance might be running a completely different operating system
1444 from the library and error numbers are not standardized across
1445 Un*xen). If this could not be done, then the error is translated to
1446 C<EINVAL>. In practice this should only happen in very rare
1449 =head2 guestfs_set_error_handler
1451 typedef void (*guestfs_error_handler_cb) (guestfs_h *g,
1454 void guestfs_set_error_handler (guestfs_h *g,
1455 guestfs_error_handler_cb cb,
1458 The callback C<cb> will be called if there is an error. The
1459 parameters passed to the callback are an opaque data pointer and the
1460 error message string.
1462 C<errno> is not passed to the callback. To get that the callback must
1463 call L</guestfs_last_errno>.
1465 Note that the message string C<msg> is freed as soon as the callback
1466 function returns, so if you want to stash it somewhere you must make
1469 The default handler prints messages on C<stderr>.
1471 If you set C<cb> to C<NULL> then I<no> handler is called.
1473 =head2 guestfs_get_error_handler
1475 guestfs_error_handler_cb guestfs_get_error_handler (guestfs_h *g,
1478 Returns the current error handler callback.
1480 =head2 guestfs_set_out_of_memory_handler
1482 typedef void (*guestfs_abort_cb) (void);
1483 void guestfs_set_out_of_memory_handler (guestfs_h *g,
1486 The callback C<cb> will be called if there is an out of memory
1487 situation. I<Note this callback must not return>.
1489 The default is to call L<abort(3)>.
1491 You cannot set C<cb> to C<NULL>. You can't ignore out of memory
1494 =head2 guestfs_get_out_of_memory_handler
1496 guestfs_abort_fn guestfs_get_out_of_memory_handler (guestfs_h *g);
1498 This returns the current out of memory handler.
1510 =head2 GROUPS OF FUNCTIONALITY IN THE APPLIANCE
1512 Using L</guestfs_available> you can test availability of
1513 the following groups of functions. This test queries the
1514 appliance to see if the appliance you are currently using
1515 supports the functionality.
1519 =head2 GUESTFISH supported COMMAND
1521 In L<guestfish(3)> there is a handy interactive command
1522 C<supported> which prints out the available groups and
1523 whether they are supported by this build of libguestfs.
1524 Note however that you have to do C<run> first.
1526 =head2 SINGLE CALLS AT COMPILE TIME
1528 Since version 1.5.8, C<E<lt>guestfs.hE<gt>> defines symbols
1529 for each C API function, such as:
1531 #define LIBGUESTFS_HAVE_DD 1
1533 if L</guestfs_dd> is available.
1535 Before version 1.5.8, if you needed to test whether a single
1536 libguestfs function is available at compile time, we recommended using
1537 build tools such as autoconf or cmake. For example in autotools you
1540 AC_CHECK_LIB([guestfs],[guestfs_create])
1541 AC_CHECK_FUNCS([guestfs_dd])
1543 which would result in C<HAVE_GUESTFS_DD> being either defined
1544 or not defined in your program.
1546 =head2 SINGLE CALLS AT RUN TIME
1548 Testing at compile time doesn't guarantee that a function really
1549 exists in the library. The reason is that you might be dynamically
1550 linked against a previous I<libguestfs.so> (dynamic library)
1551 which doesn't have the call. This situation unfortunately results
1552 in a segmentation fault, which is a shortcoming of the C dynamic
1553 linking system itself.
1555 You can use L<dlopen(3)> to test if a function is available
1556 at run time, as in this example program (note that you still
1557 need the compile time check as well):
1563 #include <guestfs.h>
1567 #ifdef LIBGUESTFS_HAVE_DD
1571 /* Test if the function guestfs_dd is really available. */
1572 dl = dlopen (NULL, RTLD_LAZY);
1574 fprintf (stderr, "dlopen: %s\n", dlerror ());
1575 exit (EXIT_FAILURE);
1577 has_function = dlsym (dl, "guestfs_dd") != NULL;
1581 printf ("this libguestfs.so does NOT have guestfs_dd function\n");
1583 printf ("this libguestfs.so has guestfs_dd function\n");
1584 /* Now it's safe to call
1585 guestfs_dd (g, "foo", "bar");
1589 printf ("guestfs_dd function was not found at compile time\n");
1593 You may think the above is an awful lot of hassle, and it is.
1594 There are other ways outside of the C linking system to ensure
1595 that this kind of incompatibility never arises, such as using
1598 Requires: libguestfs >= 1.0.80
1600 =head1 CALLS WITH OPTIONAL ARGUMENTS
1602 A recent feature of the API is the introduction of calls which take
1603 optional arguments. In C these are declared 3 ways. The main way is
1604 as a call which takes variable arguments (ie. C<...>), as in this
1607 int guestfs_add_drive_opts (guestfs_h *g, const char *filename, ...);
1609 Call this with a list of optional arguments, terminated by C<-1>.
1610 So to call with no optional arguments specified:
1612 guestfs_add_drive_opts (g, filename, -1);
1614 With a single optional argument:
1616 guestfs_add_drive_opts (g, filename,
1617 GUESTFS_ADD_DRIVE_OPTS_FORMAT, "qcow2",
1622 guestfs_add_drive_opts (g, filename,
1623 GUESTFS_ADD_DRIVE_OPTS_FORMAT, "qcow2",
1624 GUESTFS_ADD_DRIVE_OPTS_READONLY, 1,
1627 and so forth. Don't forget the terminating C<-1> otherwise
1628 Bad Things will happen!
1630 =head2 USING va_list FOR OPTIONAL ARGUMENTS
1632 The second variant has the same name with the suffix C<_va>, which
1633 works the same way but takes a C<va_list>. See the C manual for
1634 details. For the example function, this is declared:
1636 int guestfs_add_drive_opts_va (guestfs_h *g, const char *filename,
1639 =head2 CONSTRUCTING OPTIONAL ARGUMENTS
1641 The third variant is useful where you need to construct these
1642 calls. You pass in a structure where you fill in the optional
1643 fields. The structure has a bitmask as the first element which
1644 you must set to indicate which fields you have filled in. For
1645 our example function the structure and call are declared:
1647 struct guestfs_add_drive_opts_argv {
1653 int guestfs_add_drive_opts_argv (guestfs_h *g, const char *filename,
1654 const struct guestfs_add_drive_opts_argv *optargs);
1656 You could call it like this:
1658 struct guestfs_add_drive_opts_argv optargs = {
1659 .bitmask = GUESTFS_ADD_DRIVE_OPTS_READONLY_BITMASK |
1660 GUESTFS_ADD_DRIVE_OPTS_FORMAT_BITMASK,
1665 guestfs_add_drive_opts_argv (g, filename, &optargs);
1673 The C<_BITMASK> suffix on each option name when specifying the
1678 You do not need to fill in all fields of the structure.
1682 There must be a one-to-one correspondence between fields of the
1683 structure that are filled in, and bits set in the bitmask.
1687 =head2 OPTIONAL ARGUMENTS IN OTHER LANGUAGES
1689 In other languages, optional arguments are expressed in the
1690 way that is natural for that language. We refer you to the
1691 language-specific documentation for more details on that.
1693 For guestfish, see L<guestfish(1)/OPTIONAL ARGUMENTS>.
1695 =head2 SETTING CALLBACKS TO HANDLE EVENTS
1697 B<Note:> This section documents the generic event mechanism introduced
1698 in libguestfs 1.10, which you should use in new code if possible. The
1699 old functions C<guestfs_set_log_message_callback>,
1700 C<guestfs_set_subprocess_quit_callback>,
1701 C<guestfs_set_launch_done_callback>, C<guestfs_set_close_callback> and
1702 C<guestfs_set_progress_callback> are no longer documented in this
1703 manual page. Because of the ABI guarantee, the old functions continue
1706 Handles generate events when certain things happen, such as log
1707 messages being generated, progress messages during long-running
1708 operations, or the handle being closed. The API calls described below
1709 let you register a callback to be called when events happen. You can
1710 register multiple callbacks (for the same, different or overlapping
1711 sets of events), and individually remove callbacks. If callbacks are
1712 not removed, then they remain in force until the handle is closed.
1714 In the current implementation, events are only generated
1715 synchronously: that means that events (and hence callbacks) can only
1716 happen while you are in the middle of making another libguestfs call.
1717 The callback is called in the same thread.
1719 Events may contain a payload, usually nothing (void), an array of 64
1720 bit unsigned integers, or a message buffer. Payloads are discussed
1723 =head3 CLASSES OF EVENTS
1727 =item GUESTFS_EVENT_CLOSE
1728 (payload type: void)
1730 The callback function will be called while the handle is being closed
1731 (synchronously from L</guestfs_close>).
1733 Note that libguestfs installs an L<atexit(3)> handler to try to clean
1734 up handles that are open when the program exits. This means that this
1735 callback might be called indirectly from L<exit(3)>, which can cause
1736 unexpected problems in higher-level languages (eg. if your HLL
1737 interpreter has already been cleaned up by the time this is called,
1738 and if your callback then jumps into some HLL function).
1740 If no callback is registered: the handle is closed without any
1741 callback being invoked.
1743 =item GUESTFS_EVENT_SUBPROCESS_QUIT
1744 (payload type: void)
1746 The callback function will be called when the child process quits,
1747 either asynchronously or if killed by L</guestfs_kill_subprocess>.
1748 (This corresponds to a transition from any state to the CONFIG state).
1750 If no callback is registered: the event is ignored.
1752 =item GUESTFS_EVENT_LAUNCH_DONE
1753 (payload type: void)
1755 The callback function will be called when the child process becomes
1756 ready first time after it has been launched. (This corresponds to a
1757 transition from LAUNCHING to the READY state).
1759 If no callback is registered: the event is ignored.
1761 =item GUESTFS_EVENT_PROGRESS
1762 (payload type: array of 4 x uint64_t)
1764 Some long-running operations can generate progress messages. If
1765 this callback is registered, then it will be called each time a
1766 progress message is generated (usually two seconds after the
1767 operation started, and three times per second thereafter until
1768 it completes, although the frequency may change in future versions).
1770 The callback receives in the payload four unsigned 64 bit numbers
1771 which are (in order): C<proc_nr>, C<serial>, C<position>, C<total>.
1773 The units of C<total> are not defined, although for some
1774 operations C<total> may relate in some way to the amount of
1775 data to be transferred (eg. in bytes or megabytes), and
1776 C<position> may be the portion which has been transferred.
1778 The only defined and stable parts of the API are:
1784 The callback can display to the user some type of progress bar or
1785 indicator which shows the ratio of C<position>:C<total>.
1789 0 E<lt>= C<position> E<lt>= C<total>
1793 If any progress notification is sent during a call, then a final
1794 progress notification is always sent when C<position> = C<total>
1795 (I<unless> the call fails with an error).
1797 This is to simplify caller code, so callers can easily set the
1798 progress indicator to "100%" at the end of the operation, without
1799 requiring special code to detect this case.
1803 For some calls we are unable to estimate the progress of the call, but
1804 we can still generate progress messages to indicate activity. This is
1805 known as "pulse mode", and is directly supported by certain progress
1806 bar implementations (eg. GtkProgressBar).
1808 For these calls, zero or more progress messages are generated with
1809 C<position = 0> and C<total = 1>, followed by a final message with
1810 C<position = total = 1>.
1812 As noted above, if the call fails with an error then the final message
1813 may not be generated.
1817 The callback also receives the procedure number (C<proc_nr>) and
1818 serial number (C<serial>) of the call. These are only useful for
1819 debugging protocol issues, and the callback can normally ignore them.
1820 The callback may want to print these numbers in error messages or
1823 If no callback is registered: progress messages are discarded.
1825 =item GUESTFS_EVENT_APPLIANCE
1826 (payload type: message buffer)
1828 The callback function is called whenever a log message is generated by
1829 qemu, the appliance kernel, guestfsd (daemon), or utility programs.
1831 If the verbose flag (L</guestfs_set_verbose>) is set before launch
1832 (L</guestfs_launch>) then additional debug messages are generated.
1834 If no callback is registered: the messages are discarded unless the
1835 verbose flag is set in which case they are sent to stderr. You can
1836 override the printing of verbose messages to stderr by setting up a
1839 =item GUESTFS_EVENT_LIBRARY
1840 (payload type: message buffer)
1842 The callback function is called whenever a log message is generated by
1843 the library part of libguestfs.
1845 If the verbose flag (L</guestfs_set_verbose>) is set then additional
1846 debug messages are generated.
1848 If no callback is registered: the messages are discarded unless the
1849 verbose flag is set in which case they are sent to stderr. You can
1850 override the printing of verbose messages to stderr by setting up a
1853 =item GUESTFS_EVENT_TRACE
1854 (payload type: message buffer)
1856 The callback function is called whenever a trace message is generated.
1857 This only applies if the trace flag (L</guestfs_set_trace>) is set.
1859 If no callback is registered: the messages are sent to stderr. You
1860 can override the printing of trace messages to stderr by setting up a
1863 =item GUESTFS_EVENT_ENTER
1864 (payload type: function name)
1866 The callback function is called whenever a libguestfs function
1869 The payload is a string which contains the name of the function
1870 that we are entering (not including C<guestfs_> prefix).
1872 Note that libguestfs functions can call themselves, so you may
1873 see many events from a single call. A few libguestfs functions
1874 do not generate this event.
1876 If no callback is registered: the event is ignored.
1880 =head3 guestfs_set_event_callback
1882 int guestfs_set_event_callback (guestfs_h *g,
1883 guestfs_event_callback cb,
1884 uint64_t event_bitmask,
1888 This function registers a callback (C<cb>) for all event classes
1889 in the C<event_bitmask>.
1891 For example, to register for all log message events, you could call
1892 this function with the bitmask
1893 C<GUESTFS_EVENT_APPLIANCE|GUESTFS_EVENT_LIBRARY>. To register a
1894 single callback for all possible classes of events, use
1895 C<GUESTFS_EVENT_ALL>.
1897 C<flags> should always be passed as 0.
1899 C<opaque> is an opaque pointer which is passed to the callback. You
1900 can use it for any purpose.
1902 The return value is the event handle (an integer) which you can use to
1903 delete the callback (see below).
1905 If there is an error, this function returns C<-1>, and sets the error
1906 in the handle in the usual way (see L</guestfs_last_error> etc.)
1908 Callbacks remain in effect until they are deleted, or until the handle
1911 In the case where multiple callbacks are registered for a particular
1912 event class, all of the callbacks are called. The order in which
1913 multiple callbacks are called is not defined.
1915 =head3 guestfs_delete_event_callback
1917 void guestfs_delete_event_callback (guestfs_h *g, int event_handle);
1919 Delete a callback that was previously registered. C<event_handle>
1920 should be the integer that was returned by a previous call to
1921 C<guestfs_set_event_callback> on the same handle.
1923 =head3 guestfs_event_callback
1925 typedef void (*guestfs_event_callback) (
1931 const char *buf, size_t buf_len,
1932 const uint64_t *array, size_t array_len);
1934 This is the type of the event callback function that you have to
1937 The basic parameters are: the handle (C<g>), the opaque user pointer
1938 (C<opaque>), the event class (eg. C<GUESTFS_EVENT_PROGRESS>), the
1939 event handle, and C<flags> which in the current API you should ignore.
1941 The remaining parameters contain the event payload (if any). Each
1942 event may contain a payload, which usually relates to the event class,
1943 but for future proofing your code should be written to handle any
1944 payload for any event class.
1946 C<buf> and C<buf_len> contain a message buffer (if C<buf_len == 0>,
1947 then there is no message buffer). Note that this message buffer can
1948 contain arbitrary 8 bit data, including NUL bytes.
1950 C<array> and C<array_len> is an array of 64 bit unsigned integers. At
1951 the moment this is only used for progress messages.
1953 =head3 EXAMPLE: CAPTURING LOG MESSAGES
1955 One motivation for the generic event API was to allow GUI programs to
1956 capture debug and other messages. In libguestfs E<le> 1.8 these were
1957 sent unconditionally to C<stderr>.
1959 Events associated with log messages are: C<GUESTFS_EVENT_LIBRARY>,
1960 C<GUESTFS_EVENT_APPLIANCE> and C<GUESTFS_EVENT_TRACE>. (Note that
1961 error messages are not events; you must capture error messages
1964 Programs have to set up a callback to capture the classes of events of
1968 guestfs_set_event_callback
1969 (g, message_callback,
1970 GUESTFS_EVENT_LIBRARY|GUESTFS_EVENT_APPLIANCE|
1971 GUESTFS_EVENT_TRACE,
1974 // handle error in the usual way
1977 The callback can then direct messages to the appropriate place. In
1978 this example, messages are directed to syslog:
1987 const char *buf, size_t buf_len,
1988 const uint64_t *array, size_t array_len)
1990 const int priority = LOG_USER|LOG_INFO;
1992 syslog (priority, "event 0x%lx: %s", event, buf);
1995 =head1 CANCELLING LONG TRANSFERS
1997 Some operations can be cancelled by the caller while they are in
1998 progress. Currently only operations that involve uploading or
1999 downloading data can be cancelled (technically: operations that have
2000 C<FileIn> or C<FileOut> parameters in the generator).
2002 =head2 guestfs_user_cancel
2004 void guestfs_user_cancel (guestfs_h *g);
2006 C<guestfs_user_cancel> cancels the current upload or download
2009 Unlike most other libguestfs calls, this function is signal safe and
2010 thread safe. You can call it from a signal handler or from another
2011 thread, without needing to do any locking.
2013 The transfer that was in progress (if there is one) will stop shortly
2014 afterwards, and will return an error. The errno (see
2015 L</guestfs_last_errno>) is set to C<EINTR>, so you can test for this
2016 to find out if the operation was cancelled or failed because of
2019 No cleanup is performed: for example, if a file was being uploaded
2020 then after cancellation there may be a partially uploaded file. It is
2021 the caller's responsibility to clean up if necessary.
2023 There are two common places that you might call C<guestfs_user_cancel>.
2025 In an interactive text-based program, you might call it from a
2026 C<SIGINT> signal handler so that pressing C<^C> cancels the current
2027 operation. (You also need to call L</guestfs_set_pgroup> so that
2028 child processes don't receive the C<^C> signal).
2030 In a graphical program, when the main thread is displaying a progress
2031 bar with a cancel button, wire up the cancel button to call this
2034 =head1 PRIVATE DATA AREA
2036 You can attach named pieces of private data to the libguestfs handle,
2037 fetch them by name, and walk over them, for the lifetime of the
2038 handle. This is called the private data area and is only available
2041 To attach a named piece of data, use the following call:
2043 void guestfs_set_private (guestfs_h *g, const char *key, void *data);
2045 C<key> is the name to associate with this data, and C<data> is an
2046 arbitrary pointer (which can be C<NULL>). Any previous item with the
2047 same key is overwritten.
2049 You can use any C<key> you want, but your key should I<not> start with
2050 an underscore character. Keys beginning with an underscore character
2051 are reserved for internal libguestfs purposes (eg. for implementing
2052 language bindings). It is recommended that you prefix the key with
2053 some unique string to avoid collisions with other users.
2055 To retrieve the pointer, use:
2057 void *guestfs_get_private (guestfs_h *g, const char *key);
2059 This function returns C<NULL> if either no data is found associated
2060 with C<key>, or if the user previously set the C<key>'s C<data>
2063 Libguestfs does not try to look at or interpret the C<data> pointer in
2064 any way. As far as libguestfs is concerned, it need not be a valid
2065 pointer at all. In particular, libguestfs does I<not> try to free the
2066 data when the handle is closed. If the data must be freed, then the
2067 caller must either free it before calling L</guestfs_close> or must
2068 set up a close callback to do it (see L</GUESTFS_EVENT_CLOSE>).
2070 To walk over all entries, use these two functions:
2072 void *guestfs_first_private (guestfs_h *g, const char **key_rtn);
2074 void *guestfs_next_private (guestfs_h *g, const char **key_rtn);
2076 C<guestfs_first_private> returns the first key, pointer pair ("first"
2077 does not have any particular meaning -- keys are not returned in any
2078 defined order). A pointer to the key is returned in C<*key_rtn> and
2079 the corresponding data pointer is returned from the function. C<NULL>
2080 is returned if there are no keys stored in the handle.
2082 C<guestfs_next_private> returns the next key, pointer pair. The
2083 return value of this function is also C<NULL> is there are no further
2086 Notes about walking over entries:
2092 You must not call C<guestfs_set_private> while walking over the
2097 The handle maintains an internal iterator which is reset when you call
2098 C<guestfs_first_private>. This internal iterator is invalidated when
2099 you call C<guestfs_set_private>.
2103 If you have set the data pointer associated with a key to C<NULL>, ie:
2105 guestfs_set_private (g, key, NULL);
2107 then that C<key> is not returned when walking.
2111 C<*key_rtn> is only valid until the next call to
2112 C<guestfs_first_private>, C<guestfs_next_private> or
2113 C<guestfs_set_private>.
2117 The following example code shows how to print all keys and data
2118 pointers that are associated with the handle C<g>:
2121 void *data = guestfs_first_private (g, &key);
2122 while (data != NULL)
2124 printf ("key = %s, data = %p\n", key, data);
2125 data = guestfs_next_private (g, &key);
2128 More commonly you are only interested in keys that begin with an
2129 application-specific prefix C<foo_>. Modify the loop like so:
2132 void *data = guestfs_first_private (g, &key);
2133 while (data != NULL)
2135 if (strncmp (key, "foo_", strlen ("foo_")) == 0)
2136 printf ("key = %s, data = %p\n", key, data);
2137 data = guestfs_next_private (g, &key);
2140 If you need to modify keys while walking, then you have to jump back
2141 to the beginning of the loop. For example, to delete all keys
2142 prefixed with C<foo_>:
2147 data = guestfs_first_private (g, &key);
2148 while (data != NULL)
2150 if (strncmp (key, "foo_", strlen ("foo_")) == 0)
2152 guestfs_set_private (g, key, NULL);
2153 /* note that 'key' pointer is now invalid, and so is
2154 the internal iterator */
2157 data = guestfs_next_private (g, &key);
2160 Note that the above loop is guaranteed to terminate because the keys
2161 are being deleted, but other manipulations of keys within the loop
2162 might not terminate unless you also maintain an indication of which
2163 keys have been visited.
2167 <!-- old anchor for the next section -->
2168 <a name="state_machine_and_low_level_event_api"/>
2174 Internally, libguestfs is implemented by running an appliance (a
2175 special type of small virtual machine) using L<qemu(1)>. Qemu runs as
2176 a child process of the main program.
2182 | | child process / appliance
2183 | | __________________________
2185 +-------------------+ RPC | +-----------------+ |
2186 | libguestfs <--------------------> guestfsd | |
2187 | | | +-----------------+ |
2188 \___________________/ | | Linux kernel | |
2189 | +--^--------------+ |
2190 \_________|________________/
2198 The library, linked to the main program, creates the child process and
2199 hence the appliance in the L</guestfs_launch> function.
2201 Inside the appliance is a Linux kernel and a complete stack of
2202 userspace tools (such as LVM and ext2 programs) and a small
2203 controlling daemon called L</guestfsd>. The library talks to
2204 L</guestfsd> using remote procedure calls (RPC). There is a mostly
2205 one-to-one correspondence between libguestfs API calls and RPC calls
2206 to the daemon. Lastly the disk image(s) are attached to the qemu
2207 process which translates device access by the appliance's Linux kernel
2208 into accesses to the image.
2210 A common misunderstanding is that the appliance "is" the virtual
2211 machine. Although the disk image you are attached to might also be
2212 used by some virtual machine, libguestfs doesn't know or care about
2213 this. (But you will care if both libguestfs's qemu process and your
2214 virtual machine are trying to update the disk image at the same time,
2215 since these usually results in massive disk corruption).
2217 =head1 STATE MACHINE
2219 libguestfs uses a state machine to model the child process:
2230 / | \ \ guestfs_launch
2241 \______/ <------ \________/
2243 The normal transitions are (1) CONFIG (when the handle is created, but
2244 there is no child process), (2) LAUNCHING (when the child process is
2245 booting up), (3) alternating between READY and BUSY as commands are
2246 issued to, and carried out by, the child process.
2248 The guest may be killed by L</guestfs_kill_subprocess>, or may die
2249 asynchronously at any time (eg. due to some internal error), and that
2250 causes the state to transition back to CONFIG.
2252 Configuration commands for qemu such as L</guestfs_add_drive> can only
2253 be issued when in the CONFIG state.
2255 The API offers one call that goes from CONFIG through LAUNCHING to
2256 READY. L</guestfs_launch> blocks until the child process is READY to
2257 accept commands (or until some failure or timeout).
2258 L</guestfs_launch> internally moves the state from CONFIG to LAUNCHING
2259 while it is running.
2261 API actions such as L</guestfs_mount> can only be issued when in the
2262 READY state. These API calls block waiting for the command to be
2263 carried out (ie. the state to transition to BUSY and then back to
2264 READY). There are no non-blocking versions, and no way to issue more
2265 than one command per handle at the same time.
2267 Finally, the child process sends asynchronous messages back to the
2268 main program, such as kernel log messages. You can register a
2269 callback to receive these messages.
2273 =head2 APPLIANCE BOOT PROCESS
2275 This process has evolved and continues to evolve. The description
2276 here corresponds only to the current version of libguestfs and is
2277 provided for information only.
2279 In order to follow the stages involved below, enable libguestfs
2280 debugging (set the environment variable C<LIBGUESTFS_DEBUG=1>).
2284 =item Create the appliance
2286 C<febootstrap-supermin-helper> is invoked to create the kernel, a
2287 small initrd and the appliance.
2289 The appliance is cached in C</var/tmp/.guestfs-E<lt>UIDE<gt>> (or in
2290 another directory if C<TMPDIR> is set).
2292 For a complete description of how the appliance is created and cached,
2293 read the L<febootstrap(8)> and L<febootstrap-supermin-helper(8)> man
2296 =item Start qemu and boot the kernel
2298 qemu is invoked to boot the kernel.
2300 =item Run the initrd
2302 C<febootstrap-supermin-helper> builds a small initrd. The initrd is
2303 not the appliance. The purpose of the initrd is to load enough kernel
2304 modules in order that the appliance itself can be mounted and started.
2306 The initrd is a cpio archive called
2307 C</var/tmp/.guestfs-E<lt>UIDE<gt>/initrd>.
2309 When the initrd has started you will see messages showing that kernel
2310 modules are being loaded, similar to this:
2312 febootstrap: ext2 mini initrd starting up
2313 febootstrap: mounting /sys
2314 febootstrap: internal insmod libcrc32c.ko
2315 febootstrap: internal insmod crc32c-intel.ko
2317 =item Find and mount the appliance device
2319 The appliance is a sparse file containing an ext2 filesystem which
2320 contains a familiar (although reduced in size) Linux operating system.
2321 It would normally be called C</var/tmp/.guestfs-E<lt>UIDE<gt>/root>.
2323 The regular disks being inspected by libguestfs are the first
2324 devices exposed by qemu (eg. as C</dev/vda>).
2326 The last disk added to qemu is the appliance itself (eg. C</dev/vdb>
2327 if there was only one regular disk).
2329 Thus the final job of the initrd is to locate the appliance disk,
2330 mount it, and switch root into the appliance, and run C</init> from
2333 If this works successfully you will see messages such as:
2335 febootstrap: picked /sys/block/vdb/dev as root device
2336 febootstrap: creating /dev/root as block special 252:16
2337 febootstrap: mounting new root on /root
2339 Starting /init script ...
2341 Note that C<Starting /init script ...> indicates that the appliance's
2342 init script is now running.
2344 =item Initialize the appliance
2346 The appliance itself now initializes itself. This involves starting
2347 certain processes like C<udev>, possibly printing some debug
2348 information, and finally running the daemon (C<guestfsd>).
2352 Finally the daemon (C<guestfsd>) runs inside the appliance. If it
2353 runs you should see:
2355 verbose daemon enabled
2357 The daemon expects to see a named virtio-serial port exposed by qemu
2358 and connected on the other end to the library.
2360 The daemon connects to this port (and hence to the library) and sends
2361 a four byte message C<GUESTFS_LAUNCH_FLAG>, which initiates the
2362 communication protocol (see below).
2366 =head2 COMMUNICATION PROTOCOL
2368 Don't rely on using this protocol directly. This section documents
2369 how it currently works, but it may change at any time.
2371 The protocol used to talk between the library and the daemon running
2372 inside the qemu virtual machine is a simple RPC mechanism built on top
2373 of XDR (RFC 1014, RFC 1832, RFC 4506).
2375 The detailed format of structures is in C<src/guestfs_protocol.x>
2376 (note: this file is automatically generated).
2378 There are two broad cases, ordinary functions that don't have any
2379 C<FileIn> and C<FileOut> parameters, which are handled with very
2380 simple request/reply messages. Then there are functions that have any
2381 C<FileIn> or C<FileOut> parameters, which use the same request and
2382 reply messages, but they may also be followed by files sent using a
2385 =head3 ORDINARY FUNCTIONS (NO FILEIN/FILEOUT PARAMS)
2387 For ordinary functions, the request message is:
2389 total length (header + arguments,
2390 but not including the length word itself)
2391 struct guestfs_message_header (encoded as XDR)
2392 struct guestfs_<foo>_args (encoded as XDR)
2394 The total length field allows the daemon to allocate a fixed size
2395 buffer into which it slurps the rest of the message. As a result, the
2396 total length is limited to C<GUESTFS_MESSAGE_MAX> bytes (currently
2397 4MB), which means the effective size of any request is limited to
2398 somewhere under this size.
2400 Note also that many functions don't take any arguments, in which case
2401 the C<guestfs_I<foo>_args> is completely omitted.
2403 The header contains the procedure number (C<guestfs_proc>) which is
2404 how the receiver knows what type of args structure to expect, or none
2407 For functions that take optional arguments, the optional arguments are
2408 encoded in the C<guestfs_I<foo>_args> structure in the same way as
2409 ordinary arguments. A bitmask in the header indicates which optional
2410 arguments are meaningful. The bitmask is also checked to see if it
2411 contains bits set which the daemon does not know about (eg. if more
2412 optional arguments were added in a later version of the library), and
2413 this causes the call to be rejected.
2415 The reply message for ordinary functions is:
2417 total length (header + ret,
2418 but not including the length word itself)
2419 struct guestfs_message_header (encoded as XDR)
2420 struct guestfs_<foo>_ret (encoded as XDR)
2422 As above the C<guestfs_I<foo>_ret> structure may be completely omitted
2423 for functions that return no formal return values.
2425 As above the total length of the reply is limited to
2426 C<GUESTFS_MESSAGE_MAX>.
2428 In the case of an error, a flag is set in the header, and the reply
2429 message is slightly changed:
2431 total length (header + error,
2432 but not including the length word itself)
2433 struct guestfs_message_header (encoded as XDR)
2434 struct guestfs_message_error (encoded as XDR)
2436 The C<guestfs_message_error> structure contains the error message as a
2439 =head3 FUNCTIONS THAT HAVE FILEIN PARAMETERS
2441 A C<FileIn> parameter indicates that we transfer a file I<into> the
2442 guest. The normal request message is sent (see above). However this
2443 is followed by a sequence of file chunks.
2445 total length (header + arguments,
2446 but not including the length word itself,
2447 and not including the chunks)
2448 struct guestfs_message_header (encoded as XDR)
2449 struct guestfs_<foo>_args (encoded as XDR)
2450 sequence of chunks for FileIn param #0
2451 sequence of chunks for FileIn param #1 etc.
2453 The "sequence of chunks" is:
2455 length of chunk (not including length word itself)
2456 struct guestfs_chunk (encoded as XDR)
2458 struct guestfs_chunk (encoded as XDR)
2461 struct guestfs_chunk (with data.data_len == 0)
2463 The final chunk has the C<data_len> field set to zero. Additionally a
2464 flag is set in the final chunk to indicate either successful
2465 completion or early cancellation.
2467 At time of writing there are no functions that have more than one
2468 FileIn parameter. However this is (theoretically) supported, by
2469 sending the sequence of chunks for each FileIn parameter one after
2470 another (from left to right).
2472 Both the library (sender) I<and> the daemon (receiver) may cancel the
2473 transfer. The library does this by sending a chunk with a special
2474 flag set to indicate cancellation. When the daemon sees this, it
2475 cancels the whole RPC, does I<not> send any reply, and goes back to
2476 reading the next request.
2478 The daemon may also cancel. It does this by writing a special word
2479 C<GUESTFS_CANCEL_FLAG> to the socket. The library listens for this
2480 during the transfer, and if it gets it, it will cancel the transfer
2481 (it sends a cancel chunk). The special word is chosen so that even if
2482 cancellation happens right at the end of the transfer (after the
2483 library has finished writing and has started listening for the reply),
2484 the "spurious" cancel flag will not be confused with the reply
2487 This protocol allows the transfer of arbitrary sized files (no 32 bit
2488 limit), and also files where the size is not known in advance
2489 (eg. from pipes or sockets). However the chunks are rather small
2490 (C<GUESTFS_MAX_CHUNK_SIZE>), so that neither the library nor the
2491 daemon need to keep much in memory.
2493 =head3 FUNCTIONS THAT HAVE FILEOUT PARAMETERS
2495 The protocol for FileOut parameters is exactly the same as for FileIn
2496 parameters, but with the roles of daemon and library reversed.
2498 total length (header + ret,
2499 but not including the length word itself,
2500 and not including the chunks)
2501 struct guestfs_message_header (encoded as XDR)
2502 struct guestfs_<foo>_ret (encoded as XDR)
2503 sequence of chunks for FileOut param #0
2504 sequence of chunks for FileOut param #1 etc.
2506 =head3 INITIAL MESSAGE
2508 When the daemon launches it sends an initial word
2509 (C<GUESTFS_LAUNCH_FLAG>) which indicates that the guest and daemon is
2510 alive. This is what L</guestfs_launch> waits for.
2512 =head3 PROGRESS NOTIFICATION MESSAGES
2514 The daemon may send progress notification messages at any time. These
2515 are distinguished by the normal length word being replaced by
2516 C<GUESTFS_PROGRESS_FLAG>, followed by a fixed size progress message.
2518 The library turns them into progress callbacks (see
2519 L</GUESTFS_EVENT_PROGRESS>) if there is a callback registered, or
2520 discards them if not.
2522 The daemon self-limits the frequency of progress messages it sends
2523 (see C<daemon/proto.c:notify_progress>). Not all calls generate
2526 =head1 LIBGUESTFS VERSION NUMBERS
2528 Since April 2010, libguestfs has started to make separate development
2529 and stable releases, along with corresponding branches in our git
2530 repository. These separate releases can be identified by version
2533 even numbers for stable: 1.2.x, 1.4.x, ...
2534 .-------- odd numbers for development: 1.3.x, 1.5.x, ...
2540 | `-------- sub-version
2542 `------ always '1' because we don't change the ABI
2544 Thus "1.3.5" is the 5th update to the development branch "1.3".
2546 As time passes we cherry pick fixes from the development branch and
2547 backport those into the stable branch, the effect being that the
2548 stable branch should get more stable and less buggy over time. So the
2549 stable releases are ideal for people who don't need new features but
2550 would just like the software to work.
2552 Our criteria for backporting changes are:
2558 Documentation changes which don't affect any code are
2559 backported unless the documentation refers to a future feature
2560 which is not in stable.
2564 Bug fixes which are not controversial, fix obvious problems, and
2565 have been well tested are backported.
2569 Simple rearrangements of code which shouldn't affect how it works get
2570 backported. This is so that the code in the two branches doesn't get
2571 too far out of step, allowing us to backport future fixes more easily.
2575 We I<don't> backport new features, new APIs, new tools etc, except in
2576 one exceptional case: the new feature is required in order to
2577 implement an important bug fix.
2581 A new stable branch starts when we think the new features in
2582 development are substantial and compelling enough over the current
2583 stable branch to warrant it. When that happens we create new stable
2584 and development versions 1.N.0 and 1.(N+1).0 [N is even]. The new
2585 dot-oh release won't necessarily be so stable at this point, but by
2586 backporting fixes from development, that branch will stabilize over
2589 =head1 EXTENDING LIBGUESTFS
2591 =head2 ADDING A NEW API ACTION
2593 Large amounts of boilerplate code in libguestfs (RPC, bindings,
2594 documentation) are generated, and this makes it easy to extend the
2597 To add a new API action there are two changes:
2603 You need to add a description of the call (name, parameters, return
2604 type, tests, documentation) to C<generator/generator_actions.ml>.
2606 There are two sorts of API action, depending on whether the call goes
2607 through to the daemon in the appliance, or is serviced entirely by the
2608 library (see L</ARCHITECTURE> above). L</guestfs_sync> is an example
2609 of the former, since the sync is done in the appliance.
2610 L</guestfs_set_trace> is an example of the latter, since a trace flag
2611 is maintained in the handle and all tracing is done on the library
2614 Most new actions are of the first type, and get added to the
2615 C<daemon_functions> list. Each function has a unique procedure number
2616 used in the RPC protocol which is assigned to that action when we
2617 publish libguestfs and cannot be reused. Take the latest procedure
2618 number and increment it.
2620 For library-only actions of the second type, add to the
2621 C<non_daemon_functions> list. Since these functions are serviced by
2622 the library and do not travel over the RPC mechanism to the daemon,
2623 these functions do not need a procedure number, and so the procedure
2624 number is set to C<-1>.
2628 Implement the action (in C):
2630 For daemon actions, implement the function C<do_E<lt>nameE<gt>> in the
2631 C<daemon/> directory.
2633 For library actions, implement the function C<guestfs__E<lt>nameE<gt>>
2634 (note: double underscore) in the C<src/> directory.
2636 In either case, use another function as an example of what to do.
2640 After making these changes, use C<make> to compile.
2642 Note that you don't need to implement the RPC, language bindings,
2643 manual pages or anything else. It's all automatically generated from
2644 the OCaml description.
2646 =head2 ADDING TESTS FOR AN API ACTION
2648 You can supply zero or as many tests as you want per API call. The
2649 tests can either be added as part of the API description
2650 (C<generator/generator_actions.ml>), or in some rarer cases you may
2651 want to drop a script into C<regressions/>. Note that adding a script
2652 to C<regressions/> is slower, so if possible use the first method.
2654 The following describes the test environment used when you add an API
2655 test in C<generator_actions.ml>.
2657 The test environment has 4 block devices:
2661 =item C</dev/sda> 500MB
2663 General block device for testing.
2665 =item C</dev/sdb> 50MB
2667 C</dev/sdb1> is an ext2 filesystem used for testing
2668 filesystem write operations.
2670 =item C</dev/sdc> 10MB
2672 Used in a few tests where two block devices are needed.
2676 ISO with fixed content (see C<images/test.iso>).
2680 To be able to run the tests in a reasonable amount of time, the
2681 libguestfs appliance and block devices are reused between tests. So
2682 don't try testing L</guestfs_kill_subprocess> :-x
2684 Each test starts with an initial scenario, selected using one of the
2685 C<Init*> expressions, described in C<generator/generator_types.ml>.
2686 These initialize the disks mentioned above in a particular way as
2687 documented in C<generator_types.ml>. You should not assume anything
2688 about the previous contents of other disks that are not initialized.
2690 You can add a prerequisite clause to any individual test. This is a
2691 run-time check, which, if it fails, causes the test to be skipped.
2692 Useful if testing a command which might not work on all variations of
2693 libguestfs builds. A test that has prerequisite of C<Always> means to
2694 run unconditionally.
2696 In addition, packagers can skip individual tests by setting
2697 environment variables before running C<make check>.
2699 SKIP_TEST_<CMD>_<NUM>=1
2701 eg: C<SKIP_TEST_COMMAND_3=1> skips test #3 of L</guestfs_command>.
2707 eg: C<SKIP_TEST_ZEROFREE=1> skips all L</guestfs_zerofree> tests.
2709 Packagers can run only certain tests by setting for example:
2711 TEST_ONLY="vfs_type zerofree"
2713 See C<capitests/tests.c> for more details of how these environment
2716 =head2 DEBUGGING NEW API ACTIONS
2718 Test new actions work before submitting them.
2720 You can use guestfish to try out new commands.
2722 Debugging the daemon is a problem because it runs inside a minimal
2723 environment. However you can fprintf messages in the daemon to
2724 stderr, and they will show up if you use C<guestfish -v>.
2726 =head2 FORMATTING CODE AND OTHER CONVENTIONS
2728 Our C source code generally adheres to some basic code-formatting
2729 conventions. The existing code base is not totally consistent on this
2730 front, but we do prefer that contributed code be formatted similarly.
2731 In short, use spaces-not-TABs for indentation, use 2 spaces for each
2732 indentation level, and other than that, follow the K&R style.
2734 If you use Emacs, add the following to one of one of your start-up files
2735 (e.g., ~/.emacs), to help ensure that you get indentation right:
2737 ;;; In libguestfs, indent with spaces everywhere (not TABs).
2738 ;;; Exceptions: Makefile and ChangeLog modes.
2739 (add-hook 'find-file-hook
2740 '(lambda () (if (and buffer-file-name
2741 (string-match "/libguestfs\\>"
2743 (not (string-equal mode-name "Change Log"))
2744 (not (string-equal mode-name "Makefile")))
2745 (setq indent-tabs-mode nil))))
2747 ;;; When editing C sources in libguestfs, use this style.
2748 (defun libguestfs-c-mode ()
2749 "C mode with adjusted defaults for use with libguestfs."
2752 (setq c-indent-level 2)
2753 (setq c-basic-offset 2))
2754 (add-hook 'c-mode-hook
2755 '(lambda () (if (string-match "/libguestfs\\>"
2757 (libguestfs-c-mode))))
2759 Enable warnings when compiling (and fix any problems this
2762 ./configure --enable-gcc-warnings
2766 make syntax-check # checks the syntax of the C code
2767 make check # runs the test suite
2769 =head2 DAEMON CUSTOM PRINTF FORMATTERS
2771 In the daemon code we have created custom printf formatters C<%Q> and
2772 C<%R>, which are used to do shell quoting.
2778 Simple shell quoted string. Any spaces or other shell characters are
2783 Same as C<%Q> except the string is treated as a path which is prefixed
2790 asprintf (&cmd, "cat %R", path);
2792 would produce C<cat /sysroot/some\ path\ with\ spaces>
2794 I<Note:> Do I<not> use these when you are passing parameters to the
2795 C<command{,r,v,rv}()> functions. These parameters do NOT need to be
2796 quoted because they are not passed via the shell (instead, straight to
2797 exec). You probably want to use the C<sysroot_path()> function
2800 =head2 SUBMITTING YOUR NEW API ACTIONS
2802 Submit patches to the mailing list:
2803 L<http://www.redhat.com/mailman/listinfo/libguestfs>
2804 and CC to L<rjones@redhat.com>.
2806 =head2 INTERNATIONALIZATION (I18N) SUPPORT
2808 We support i18n (gettext anyhow) in the library.
2810 However many messages come from the daemon, and we don't translate
2811 those at the moment. One reason is that the appliance generally has
2812 all locale files removed from it, because they take up a lot of space.
2813 So we'd have to readd some of those, as well as copying our PO files
2816 Debugging messages are never translated, since they are intended for
2819 =head2 SOURCE CODE SUBDIRECTORIES
2825 The libguestfs appliance, build scripts and so on.
2829 Automated tests of the C API.
2833 The L<virt-cat(1)>, L<virt-filesystems(1)> and L<virt-ls(1)> commands
2838 Safety and liveness tests of components that libguestfs depends upon
2839 (not of libguestfs itself). Mainly this is for qemu and the kernel.
2843 Outside contributions, experimental parts.
2847 The daemon that runs inside the libguestfs appliance and carries out
2852 L<virt-df(1)> command and documentation.
2856 L<virt-edit(1)> command and documentation.
2864 L<guestfish(1)>, the command-line shell, and various shell scripts
2865 built on top such as L<virt-copy-in(1)>, L<virt-copy-out(1)>,
2866 L<virt-tar-in(1)>, L<virt-tar-out(1)>.
2870 L<guestmount(1)>, FUSE (userspace filesystem) built on top of libguestfs.
2874 The crucially important generator, used to automatically generate
2875 large amounts of boilerplate C code for things like RPC and bindings.
2879 Files used by the test suite.
2881 Some "phony" guest images which we test against.
2885 L<virt-inspector(1)>, the virtual machine image inspector.
2889 Logo used on the website. The fish is called Arthur by the way.
2893 M4 macros used by autoconf.
2897 Translations of simple gettext strings.
2901 The build infrastructure and PO files for translations of manpages and
2902 POD files. Eventually this will be combined with the C<po> directory,
2903 but that is rather complicated.
2905 =item C<regressions>
2911 L<virt-rescue(1)> command and documentation.
2915 Source code to the C library.
2919 Command line tools written in Perl (L<virt-resize(1)> and many others).
2923 Test tool for end users to test if their qemu/kernel combination
2924 will work with libguestfs.
2948 =head2 MAKING A STABLE RELEASE
2950 When we make a stable release, there are several steps documented
2951 here. See L</LIBGUESTFS VERSION NUMBERS> for general information
2952 about the stable branch policy.
2958 Check C<make && make check> works on at least Fedora, Debian and
2963 Finalize RELEASE-NOTES.
2971 Run C<src/api-support/update-from-tarballs.sh>.
2975 Push and pull from Transifex.
2981 to push the latest POT files to Transifex. Then run:
2985 which is a wrapper to pull the latest translated C<*.po> files.
2989 Create new stable and development directories under
2990 L<http://libguestfs.org/download>.
2994 Create the branch in git:
2996 git tag -a 1.XX.0 -m "Version 1.XX.0 (stable)"
2997 git tag -a 1.YY.0 -m "Version 1.YY.0 (development)"
2998 git branch stable-1.XX
2999 git push origin tag 1.XX.0 1.YY.0 stable-1.XX
3005 =head2 PROTOCOL LIMITS
3007 Internally libguestfs uses a message-based protocol to pass API calls
3008 and their responses to and from a small "appliance" (see L</INTERNALS>
3009 for plenty more detail about this). The maximum message size used by
3010 the protocol is slightly less than 4 MB. For some API calls you may
3011 need to be aware of this limit. The API calls which may be affected
3012 are individually documented, with a link back to this section of the
3015 A simple call such as L</guestfs_cat> returns its result (the file
3016 data) in a simple string. Because this string is at some point
3017 internally encoded as a message, the maximum size that it can return
3018 is slightly under 4 MB. If the requested file is larger than this
3019 then you will get an error.
3021 In order to transfer large files into and out of the guest filesystem,
3022 you need to use particular calls that support this. The sections
3023 L</UPLOADING> and L</DOWNLOADING> document how to do this.
3025 You might also consider mounting the disk image using our FUSE
3026 filesystem support (L<guestmount(1)>).
3028 =head2 MAXIMUM NUMBER OF DISKS
3030 When using virtio disks (the default) the current limit is B<25>
3033 Virtio itself consumes 1 virtual PCI slot per disk, and PCI is limited
3034 to 31 slots. However febootstrap only understands disks with names
3035 C</dev/vda> through C</dev/vdz> (26 letters) and it reserves one disk
3036 for its own purposes.
3038 We are working to substantially raise this limit in future versions
3039 but it requires complex changes to qemu.
3041 In future versions of libguestfs it should also be possible to "hot
3042 plug" disks (add and remove disks after calling L</guestfs_launch>).
3043 This also requires changes to qemu.
3045 =head2 MAXIMUM NUMBER OF PARTITIONS PER DISK
3047 Virtio limits the maximum number of partitions per disk to B<15>.
3049 This is because it reserves 4 bits for the minor device number (thus
3050 C</dev/vda>, and C</dev/vda1> through C</dev/vda15>).
3052 If you attach a disk with more than 15 partitions, the extra
3053 partitions are ignored by libguestfs.
3055 =head2 MAXIMUM SIZE OF A DISK
3057 Probably the limit is between 2**63-1 and 2**64-1 bytes.
3059 We have tested block devices up to 1 exabyte (2**60 or
3060 1,152,921,504,606,846,976 bytes) using sparse files backed by an XFS
3063 Although libguestfs probably does not impose any limit, the underlying
3064 host storage will. If you store disk images on a host ext4
3065 filesystem, then the maximum size will be limited by the maximum ext4
3066 file size (currently 16 TB). If you store disk images as host logical
3067 volumes then you are limited by the maximum size of an LV.
3069 For the hugest disk image files, we recommend using XFS on the host
3072 =head2 MAXIMUM SIZE OF A PARTITION
3074 The MBR (ie. classic MS-DOS) partitioning scheme uses 32 bit sector
3075 numbers. Assuming a 512 byte sector size, this means that MBR cannot
3076 address a partition located beyond 2 TB on the disk.
3078 It is recommended that you use GPT partitions on disks which are
3079 larger than this size. GPT uses 64 bit sector numbers and so can
3080 address partitions which are theoretically larger than the largest
3081 disk we could support.
3083 =head2 MAXIMUM SIZE OF A FILESYSTEM, FILES, DIRECTORIES
3085 This depends on the filesystem type. libguestfs itself does not
3086 impose any known limit. Consult Wikipedia or the filesystem
3087 documentation to find out what these limits are.
3089 =head2 MAXIMUM UPLOAD AND DOWNLOAD
3091 The API functions L</guestfs_upload>, L</guestfs_download>,
3092 L</guestfs_tar_in>, L</guestfs_tar_out> and the like allow unlimited
3093 sized uploads and downloads.
3095 =head2 INSPECTION LIMITS
3097 The inspection code has several arbitrary limits on things like the
3098 size of Windows Registry hive it will read, and the length of product
3099 name. These are intended to stop a malicious guest from consuming
3100 arbitrary amounts of memory and disk space on the host, and should not
3101 be reached in practice. See the source code for more information.
3103 =head1 ENVIRONMENT VARIABLES
3107 =item FEBOOTSTRAP_KERNEL
3109 =item FEBOOTSTRAP_MODULES
3111 These two environment variables allow the kernel that libguestfs uses
3112 in the appliance to be selected. If C<$FEBOOTSTRAP_KERNEL> is not
3113 set, then the most recent host kernel is chosen. For more information
3114 about kernel selection, see L<febootstrap-supermin-helper(8)>. This
3115 feature is only available in febootstrap E<ge> 3.8.
3117 =item LIBGUESTFS_APPEND
3119 Pass additional options to the guest kernel.
3121 =item LIBGUESTFS_DEBUG
3123 Set C<LIBGUESTFS_DEBUG=1> to enable verbose messages. This
3124 has the same effect as calling C<guestfs_set_verbose (g, 1)>.
3126 =item LIBGUESTFS_MEMSIZE
3128 Set the memory allocated to the qemu process, in megabytes. For
3131 LIBGUESTFS_MEMSIZE=700
3133 =item LIBGUESTFS_PATH
3135 Set the path that libguestfs uses to search for a supermin appliance.
3136 See the discussion of paths in section L</PATH> above.
3138 =item LIBGUESTFS_QEMU
3140 Set the default qemu binary that libguestfs uses. If not set, then
3141 the qemu which was found at compile time by the configure script is
3144 See also L</QEMU WRAPPERS> above.
3146 =item LIBGUESTFS_TRACE
3148 Set C<LIBGUESTFS_TRACE=1> to enable command traces. This
3149 has the same effect as calling C<guestfs_set_trace (g, 1)>.
3153 Location of temporary directory, defaults to C</tmp> except for the
3154 cached supermin appliance which defaults to C</var/tmp>.
3156 If libguestfs was compiled to use the supermin appliance then the
3157 real appliance is cached in this directory, shared between all
3158 handles belonging to the same EUID. You can use C<$TMPDIR> to
3159 configure another directory to use in case C</var/tmp> is not large
3166 L<guestfs-examples(3)>,
3167 L<guestfs-erlang(3)>,
3169 L<guestfs-ocaml(3)>,
3171 L<guestfs-python(3)>,
3177 L<virt-copy-out(1)>,
3180 L<virt-filesystems(1)>,
3181 L<virt-inspector(1)>,
3182 L<virt-list-filesystems(1)>,
3183 L<virt-list-partitions(1)>,
3193 L<febootstrap-supermin-helper(8)>,
3195 L<http://libguestfs.org/>.
3197 Tools with a similar purpose:
3206 To get a list of bugs against libguestfs use this link:
3208 L<https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools>
3210 To report a new bug against libguestfs use this link:
3212 L<https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools>
3214 When reporting a bug, please check:
3220 That the bug hasn't been reported already.
3224 That you are testing a recent version.
3228 Describe the bug accurately, and give a way to reproduce it.
3232 Run libguestfs-test-tool and paste the B<complete, unedited>
3233 output into the bug report.
3239 Richard W.M. Jones (C<rjones at redhat dot com>)
3243 Copyright (C) 2009-2011 Red Hat Inc.
3244 L<http://libguestfs.org/>
3246 This library is free software; you can redistribute it and/or
3247 modify it under the terms of the GNU Lesser General Public
3248 License as published by the Free Software Foundation; either
3249 version 2 of the License, or (at your option) any later version.
3251 This library is distributed in the hope that it will be useful,
3252 but WITHOUT ANY WARRANTY; without even the implied warranty of
3253 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
3254 Lesser General Public License for more details.
3256 You should have received a copy of the GNU Lesser General Public
3257 License along with this library; if not, write to the Free Software
3258 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA