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, "/");
20 cc prog.c -o prog -lguestfs
22 cc prog.c -o prog `pkg-config libguestfs --cflags --libs`
26 Libguestfs is a library for accessing and modifying guest disk images.
27 Amongst the things this is good for: making batch configuration
28 changes to guests, getting disk used/free statistics (see also:
29 virt-df), migrating between virtualization systems (see also:
30 virt-p2v), performing partial backups, performing partial guest
31 clones, cloning guests and changing registry/UUID/hostname info, and
34 Libguestfs uses Linux kernel and qemu code, and can access any type of
35 guest filesystem that Linux and qemu can, including but not limited
36 to: ext2/3/4, btrfs, FAT and NTFS, LVM, many different disk partition
37 schemes, qcow, qcow2, vmdk.
39 Libguestfs provides ways to enumerate guest storage (eg. partitions,
40 LVs, what filesystem is in each LV, etc.). It can also run commands
41 in the context of the guest. Also you can access filesystems over
44 Libguestfs is a library that can be linked with C and C++ management
45 programs (or management programs written in OCaml, Perl, Python, Ruby,
46 Java, Haskell or C#). You can also use it from shell scripts or the
49 You don't need to be root to use libguestfs, although obviously you do
50 need enough permissions to access the disk images.
52 Libguestfs is a large API because it can do many things. For a gentle
53 introduction, please read the L</API OVERVIEW> section next.
57 This section provides a gentler overview of the libguestfs API. We
58 also try to group API calls together, where that may not be obvious
59 from reading about the individual calls in the main section of this
64 Before you can use libguestfs calls, you have to create a handle.
65 Then you must add at least one disk image to the handle, followed by
66 launching the handle, then performing whatever operations you want,
67 and finally closing the handle. By convention we use the single
68 letter C<g> for the name of the handle variable, although of course
69 you can use any name you want.
71 The general structure of all libguestfs-using programs looks like
74 guestfs_h *g = guestfs_create ();
76 /* Call guestfs_add_drive additional times if there are
77 * multiple disk images.
79 guestfs_add_drive (g, "guest.img");
81 /* Most manipulation calls won't work until you've launched
82 * the handle 'g'. You have to do this _after_ adding drives
83 * and _before_ other commands.
87 /* Now you can examine what partitions, LVs etc are available.
89 char **partitions = guestfs_list_partitions (g);
90 char **logvols = guestfs_lvs (g);
92 /* To access a filesystem in the image, you must mount it.
94 guestfs_mount (g, "/dev/sda1", "/");
96 /* Now you can perform filesystem actions on the guest
99 guestfs_touch (g, "/hello");
101 /* You only need to call guestfs_sync if you have made
102 * changes to the guest image. (But if you've made changes
103 * then you *must* sync). See also: guestfs_umount and
104 * guestfs_umount_all calls.
108 /* Close the handle 'g'. */
111 The code above doesn't include any error checking. In real code you
112 should check return values carefully for errors. In general all
113 functions that return integers return C<-1> on error, and all
114 functions that return pointers return C<NULL> on error. See section
115 L</ERROR HANDLING> below for how to handle errors, and consult the
116 documentation for each function call below to see precisely how they
117 return error indications.
121 The image filename (C<"guest.img"> in the example above) could be a
122 disk image from a virtual machine, a L<dd(1)> copy of a physical hard
123 disk, an actual block device, or simply an empty file of zeroes that
124 you have created through L<posix_fallocate(3)>. Libguestfs lets you
125 do useful things to all of these.
127 You can add a disk read-only using L</guestfs_add_drive_ro>, in which
128 case libguestfs won't modify the file.
130 Be extremely cautious if the disk image is in use, eg. if it is being
131 used by a virtual machine. Adding it read-write will almost certainly
132 cause disk corruption, but adding it read-only is safe.
134 You must add at least one disk image, and you may add multiple disk
135 images. In the API, the disk images are usually referred to as
136 C</dev/sda> (for the first one you added), C</dev/sdb> (for the second
139 Once L</guestfs_launch> has been called you cannot add any more images.
140 You can call L</guestfs_list_devices> to get a list of the device
141 names, in the order that you added them. See also L</BLOCK DEVICE
146 Before you can read or write files, create directories and so on in a
147 disk image that contains filesystems, you have to mount those
148 filesystems using L</guestfs_mount>. If you already know that a disk
149 image contains (for example) one partition with a filesystem on that
150 partition, then you can mount it directly:
152 guestfs_mount (g, "/dev/sda1", "/");
154 where C</dev/sda1> means literally the first partition (C<1>) of the
155 first disk image that we added (C</dev/sda>). If the disk contains
156 Linux LVM2 logical volumes you could refer to those instead (eg. C</dev/VG/LV>).
158 If you are given a disk image and you don't know what it contains then
159 you have to find out. Libguestfs can do that too: use
160 L</guestfs_list_partitions> and L</guestfs_lvs> to list possible
161 partitions and LVs, and either try mounting each to see what is
162 mountable, or else examine them with L</guestfs_vfs_type> or
163 L</guestfs_file>. Libguestfs also has a set of APIs for inspection of
164 disk images (see L</INSPECTION> below). But you might find it easier
165 to look at higher level programs built on top of libguestfs, in
166 particular L<virt-inspector(1)>.
168 To mount a disk image read-only, use L</guestfs_mount_ro>. There are
169 several other variations of the C<guestfs_mount_*> call.
171 =head2 FILESYSTEM ACCESS AND MODIFICATION
173 The majority of the libguestfs API consists of fairly low-level calls
174 for accessing and modifying the files, directories, symlinks etc on
175 mounted filesystems. There are over a hundred such calls which you
176 can find listed in detail below in this man page, and we don't even
177 pretend to cover them all in this overview.
179 Specify filenames as full paths, starting with C<"/"> and including
182 For example, if you mounted a filesystem at C<"/"> and you want to
183 read the file called C<"etc/passwd"> then you could do:
185 char *data = guestfs_cat (g, "/etc/passwd");
187 This would return C<data> as a newly allocated buffer containing the
188 full content of that file (with some conditions: see also
189 L</DOWNLOADING> below), or C<NULL> if there was an error.
191 As another example, to create a top-level directory on that filesystem
192 called C<"var"> you would do:
194 guestfs_mkdir (g, "/var");
196 To create a symlink you could do:
198 guestfs_ln_s (g, "/etc/init.d/portmap",
199 "/etc/rc3.d/S30portmap");
201 Libguestfs will reject attempts to use relative paths and there is no
202 concept of a current working directory.
204 Libguestfs can return errors in many situations: for example if the
205 filesystem isn't writable, or if a file or directory that you
206 requested doesn't exist. If you are using the C API (documented here)
207 you have to check for those error conditions after each call. (Other
208 language bindings turn these errors into exceptions).
210 File writes are affected by the per-handle umask, set by calling
211 L</guestfs_umask> and defaulting to 022. See L</UMASK>.
215 Libguestfs contains API calls to read, create and modify partition
216 tables on disk images.
218 In the common case where you want to create a single partition
219 covering the whole disk, you should use the L</guestfs_part_disk>
222 const char *parttype = "mbr";
223 if (disk_is_larger_than_2TB)
225 guestfs_part_disk (g, "/dev/sda", parttype);
227 Obviously this effectively wipes anything that was on that disk image
232 Libguestfs provides access to a large part of the LVM2 API, such as
233 L</guestfs_lvcreate> and L</guestfs_vgremove>. It won't make much sense
234 unless you familiarize yourself with the concepts of physical volumes,
235 volume groups and logical volumes.
237 This author strongly recommends reading the LVM HOWTO, online at
238 L<http://tldp.org/HOWTO/LVM-HOWTO/>.
242 Use L</guestfs_cat> to download small, text only files. This call
243 is limited to files which are less than 2 MB and which cannot contain
244 any ASCII NUL (C<\0>) characters. However it has a very simple
247 L</guestfs_read_file> can be used to read files which contain
248 arbitrary 8 bit data, since it returns a (pointer, size) pair.
249 However it is still limited to "small" files, less than 2 MB.
251 L</guestfs_download> can be used to download any file, with no
252 limits on content or size (even files larger than 4 GB).
254 To download multiple files, see L</guestfs_tar_out> and
259 It's often the case that you want to write a file or files to the disk
262 To write a small file with fixed content, use L</guestfs_write>. To
263 create a file of all zeroes, use L</guestfs_truncate_size> (sparse) or
264 L</guestfs_fallocate64> (with all disk blocks allocated). There are a
265 variety of other functions for creating test files, for example
266 L</guestfs_fill> and L</guestfs_fill_pattern>.
268 To upload a single file, use L</guestfs_upload>. This call has no
269 limits on file content or size (even files larger than 4 GB).
271 To upload multiple files, see L</guestfs_tar_in> and L</guestfs_tgz_in>.
273 However the fastest way to upload I<large numbers of arbitrary files>
274 is to turn them into a squashfs or CD ISO (see L<mksquashfs(8)> and
275 L<mkisofs(8)>), then attach this using L</guestfs_add_drive_ro>. If
276 you add the drive in a predictable way (eg. adding it last after all
277 other drives) then you can get the device name from
278 L</guestfs_list_devices> and mount it directly using
279 L</guestfs_mount_ro>. Note that squashfs images are sometimes
280 non-portable between kernel versions, and they don't support labels or
281 UUIDs. If you want to pre-build an image or you need to mount it
282 using a label or UUID, use an ISO image instead.
286 There are various different commands for copying between files and
287 devices and in and out of the guest filesystem. These are summarised
292 =item B<file> to B<file>
294 Use L</guestfs_cp> to copy a single file, or
295 L</guestfs_cp_a> to copy directories recursively.
297 =item B<file or device> to B<file or device>
299 Use L</guestfs_dd> which efficiently uses L<dd(1)>
300 to copy between files and devices in the guest.
302 Example: duplicate the contents of an LV:
304 guestfs_dd (g, "/dev/VG/Original", "/dev/VG/Copy");
306 The destination (C</dev/VG/Copy>) must be at least as large as the
307 source (C</dev/VG/Original>). To copy less than the whole
308 source device, use L</guestfs_copy_size>.
310 =item B<file on the host> to B<file or device>
312 Use L</guestfs_upload>. See L</UPLOADING> above.
314 =item B<file or device> to B<file on the host>
316 Use L</guestfs_download>. See L</DOWNLOADING> above.
322 L</guestfs_ll> is just designed for humans to read (mainly when using
323 the L<guestfish(1)>-equivalent command C<ll>).
325 L</guestfs_ls> is a quick way to get a list of files in a directory
326 from programs, as a flat list of strings.
328 L</guestfs_readdir> is a programmatic way to get a list of files in a
329 directory, plus additional information about each one. It is more
330 equivalent to using the L<readdir(3)> call on a local filesystem.
332 L</guestfs_find> and L</guestfs_find0> can be used to recursively list
335 =head2 RUNNING COMMANDS
337 Although libguestfs is a primarily an API for manipulating files
338 inside guest images, we also provide some limited facilities for
339 running commands inside guests.
341 There are many limitations to this:
347 The kernel version that the command runs under will be different
348 from what it expects.
352 If the command needs to communicate with daemons, then most likely
353 they won't be running.
357 The command will be running in limited memory.
361 Only supports Linux guests (not Windows, BSD, etc).
365 Architecture limitations (eg. won't work for a PPC guest on
370 For SELinux guests, you may need to enable SELinux and load policy
371 first. See L</SELINUX> in this manpage.
375 The two main API calls to run commands are L</guestfs_command> and
376 L</guestfs_sh> (there are also variations).
378 The difference is that L</guestfs_sh> runs commands using the shell, so
379 any shell globs, redirections, etc will work.
381 =head2 CONFIGURATION FILES
383 To read and write configuration files in Linux guest filesystems, we
384 strongly recommend using Augeas. For example, Augeas understands how
385 to read and write, say, a Linux shadow password file or X.org
386 configuration file, and so avoids you having to write that code.
388 The main Augeas calls are bound through the C<guestfs_aug_*> APIs. We
389 don't document Augeas itself here because there is excellent
390 documentation on the L<http://augeas.net/> website.
392 If you don't want to use Augeas (you fool!) then try calling
393 L</guestfs_read_lines> to get the file as a list of lines which
394 you can iterate over.
398 We support SELinux guests. To ensure that labeling happens correctly
399 in SELinux guests, you need to enable SELinux and load the guest's
406 Before launching, do:
408 guestfs_set_selinux (g, 1);
412 After mounting the guest's filesystem(s), load the policy. This
413 is best done by running the L<load_policy(8)> command in the
416 guestfs_sh (g, "/usr/sbin/load_policy");
418 (Older versions of C<load_policy> require you to specify the
419 name of the policy file).
423 Optionally, set the security context for the API. The correct
424 security context to use can only be known by inspecting the
425 guest. As an example:
427 guestfs_setcon (g, "unconfined_u:unconfined_r:unconfined_t:s0");
431 This will work for running commands and editing existing files.
433 When new files are created, you may need to label them explicitly,
434 for example by running the external command
435 C<restorecon pathname>.
439 Certain calls are affected by the current file mode creation mask (the
440 "umask"). In particular ones which create files or directories, such
441 as L</guestfs_touch>, L</guestfs_mknod> or L</guestfs_mkdir>. This
442 affects either the default mode that the file is created with or
443 modifies the mode that you supply.
445 The default umask is C<022>, so files are created with modes such as
446 C<0644> and directories with C<0755>.
448 There are two ways to avoid being affected by umask. Either set umask
449 to 0 (call C<guestfs_umask (g, 0)> early after launching). Or call
450 L</guestfs_chmod> after creating each file or directory.
452 For more information about umask, see L<umask(2)>.
454 =head2 ENCRYPTED DISKS
456 Libguestfs allows you to access Linux guests which have been
457 encrypted using whole disk encryption that conforms to the
458 Linux Unified Key Setup (LUKS) standard. This includes
459 nearly all whole disk encryption systems used by modern
462 Use L</guestfs_vfs_type> to identify LUKS-encrypted block
463 devices (it returns the string C<crypto_LUKS>).
465 Then open these devices by calling L</guestfs_luks_open>.
466 Obviously you will require the passphrase!
468 Opening a LUKS device creates a new device mapper device
469 called C</dev/mapper/mapname> (where C<mapname> is the
470 string you supply to L</guestfs_luks_open>).
471 Reads and writes to this mapper device are decrypted from and
472 encrypted to the underlying block device respectively.
474 LVM volume groups on the device can be made visible by calling
475 L</guestfs_vgscan> followed by L</guestfs_vg_activate_all>.
476 The logical volume(s) can now be mounted in the usual way.
478 Use the reverse process to close a LUKS device. Unmount
479 any logical volumes on it, deactivate the volume groups
480 by caling C<guestfs_vg_activate (g, 0, ["/dev/VG"])>.
481 Then close the mapper device by calling
482 L</guestfs_luks_close> on the C</dev/mapper/mapname>
483 device (I<not> the underlying encrypted block device).
487 Libguestfs has APIs for inspecting an unknown disk image to find out
488 if it contains operating systems. (These APIs used to be in a
489 separate Perl-only library called L<Sys::Guestfs::Lib(3)> but since
490 version 1.5.3 the most frequently used part of this library has been
491 rewritten in C and moved into the core code).
493 Add all disks belonging to the unknown virtual machine and call
494 L</guestfs_launch> in the usual way.
496 Then call L</guestfs_inspect_os>. This function uses other libguestfs
497 calls and certain heuristics, and returns a list of operating systems
498 that were found. An empty list means none were found. A single
499 element is the root filesystem of the operating system. For dual- or
500 multi-boot guests, multiple roots can be returned, each one
501 corresponding to a separate operating system. (Multi-boot virtual
502 machines are extremely rare in the world of virtualization, but since
503 this scenario can happen, we have built libguestfs to deal with it.)
505 For each root, you can then call various C<guestfs_inspect_get_*>
506 functions to get additional details about that operating system. For
507 example, call L</guestfs_inspect_get_type> to return the string
508 C<windows> or C<linux> for Windows and Linux-based operating systems
511 Un*x-like and Linux-based operating systems usually consist of several
512 filesystems which are mounted at boot time (for example, a separate
513 boot partition mounted on C</boot>). The inspection rules are able to
514 detect how filesystems correspond to mount points. Call
515 C<guestfs_inspect_get_mountpoints> to get this mapping. It might
516 return a hash table like this example:
519 / => /dev/vg_guest/lv_root
520 /usr => /dev/vg_guest/lv_usr
522 The caller can then make calls to L</guestfs_mount_options> to
523 mount the filesystems as suggested.
525 Be careful to mount filesystems in the right order (eg. C</> before
526 C</usr>). Sorting the keys of the hash by length, shortest first,
529 Inspection currently only works for some common operating systems.
530 Contributors are welcome to send patches for other operating systems
531 that we currently cannot detect.
533 Encrypted disks must be opened before inspection. See
534 L</ENCRYPTED DISKS> for more details. The L</guestfs_inspect_os>
535 function just ignores any encrypted devices.
537 A note on the implementation: The call L</guestfs_inspect_os> performs
538 inspection and caches the results in the guest handle. Subsequent
539 calls to C<guestfs_inspect_get_*> return this cached information, but
540 I<do not> re-read the disks. If you change the content of the guest
541 disks, you can redo inspection by calling L</guestfs_inspect_os>
544 =head2 SPECIAL CONSIDERATIONS FOR WINDOWS GUESTS
546 Libguestfs can mount NTFS partitions. It does this using the
547 L<http://www.ntfs-3g.org/> driver.
549 DOS and Windows still use drive letters, and the filesystems are
550 always treated as case insensitive by Windows itself, and therefore
551 you might find a Windows configuration file referring to a path like
552 C<c:\windows\system32>. When the filesystem is mounted in libguestfs,
553 that directory might be referred to as C</WINDOWS/System32>.
555 Drive letter mappings are outside the scope of libguestfs. You have
556 to use libguestfs to read the appropriate Windows Registry and
557 configuration files, to determine yourself how drives are mapped (see
558 also L<hivex(3)> and L<virt-inspector(1)>).
560 Replacing backslash characters with forward slash characters is also
561 outside the scope of libguestfs, but something that you can easily do.
563 Where we can help is in resolving the case insensitivity of paths.
564 For this, call L</guestfs_case_sensitive_path>.
566 Libguestfs also provides some help for decoding Windows Registry
567 "hive" files, through the library C<hivex> which is part of the
568 libguestfs project although ships as a separate tarball. You have to
569 locate and download the hive file(s) yourself, and then pass them to
570 C<hivex> functions. See also the programs L<hivexml(1)>,
571 L<hivexsh(1)>, L<hivexregedit(1)> and L<virt-win-reg(1)> for more help
574 =head2 USING LIBGUESTFS WITH OTHER PROGRAMMING LANGUAGES
576 Although we don't want to discourage you from using the C API, we will
577 mention here that the same API is also available in other languages.
579 The API is broadly identical in all supported languages. This means
580 that the C call C<guestfs_mount(g,path)> is
581 C<$g-E<gt>mount($path)> in Perl, C<g.mount(path)> in Python,
582 and C<Guestfs.mount g path> in OCaml. In other words, a
583 straightforward, predictable isomorphism between each language.
585 Error messages are automatically transformed
586 into exceptions if the language supports it.
588 We don't try to "object orientify" parts of the API in OO languages,
589 although contributors are welcome to write higher level APIs above
590 what we provide in their favourite languages if they wish.
596 You can use the I<guestfs.h> header file from C++ programs. The C++
597 API is identical to the C API. C++ classes and exceptions are not
602 The C# bindings are highly experimental. Please read the warnings
603 at the top of C<csharp/Libguestfs.cs>.
607 This is the only language binding that is working but incomplete.
608 Only calls which return simple integers have been bound in Haskell,
609 and we are looking for help to complete this binding.
613 Full documentation is contained in the Javadoc which is distributed
618 For documentation see the file C<guestfs.mli>.
622 For documentation see L<Sys::Guestfs(3)>.
626 For documentation do:
634 Use the Guestfs module. There is no Ruby-specific documentation, but
635 you can find examples written in Ruby in the libguestfs source.
637 =item B<shell scripts>
639 For documentation see L<guestfish(1)>.
643 =head2 LIBGUESTFS GOTCHAS
645 L<http://en.wikipedia.org/wiki/Gotcha_(programming)>: "A feature of a
646 system [...] that works in the way it is documented but is
647 counterintuitive and almost invites mistakes."
649 Since we developed libguestfs and the associated tools, there are
650 several things we would have designed differently, but are now stuck
651 with for backwards compatibility or other reasons. If there is ever a
652 libguestfs 2.0 release, you can expect these to change. Beware of
657 =item Autosync / forgetting to sync.
659 When modifying a filesystem from C or another language, you B<must>
660 unmount all filesystems and call L</guestfs_sync> explicitly before
661 you close the libguestfs handle. You can also call:
663 guestfs_set_autosync (g, 1);
665 to have the unmount/sync done automatically for you when the handle 'g'
666 is closed. (This feature is called "autosync", L</guestfs_set_autosync>
669 If you forget to do this, then it is entirely possible that your
670 changes won't be written out, or will be partially written, or (very
671 rarely) that you'll get disk corruption.
673 Note that in L<guestfish(3)> autosync is the default. So quick and
674 dirty guestfish scripts that forget to sync will work just fine, which
675 can make this very puzzling if you are trying to debug a problem.
677 =item Mount option C<-o sync> should not be the default.
679 If you use L</guestfs_mount>, then C<-o sync,noatime> are added
680 implicitly. However C<-o sync> does not add any reliability benefit,
681 but does have a very large performance impact.
683 The work around is to use L</guestfs_mount_options> and set the mount
684 options that you actually want to use.
686 =item Read-only should be the default.
688 In L<guestfish(3)>, I<--ro> should be the default, and you should
689 have to specify I<--rw> if you want to make changes to the image.
691 This would reduce the potential to corrupt live VM images.
693 Note that many filesystems change the disk when you just mount and
694 unmount, even if you didn't perform any writes. You need to use
695 L</guestfs_add_drive_ro> to guarantee that the disk is not changed.
697 =item guestfish command line is hard to use.
699 C<guestfish disk.img> doesn't do what people expect (open C<disk.img>
700 for examination). It tries to run a guestfish command C<disk.img>
701 which doesn't exist, so it fails. In earlier versions of guestfish
702 the error message was also unintuitive, but we have corrected this
703 since. Like the Bourne shell, we should have used C<guestfish -c
704 command> to run commands.
706 =item guestfish megabyte modifiers don't work right on all commands
708 In recent guestfish you can use C<1M> to mean 1 megabyte (and
709 similarly for other modifiers). What guestfish actually does is to
710 multiply the number part by the modifier part and pass the result to
711 the C API. However this doesn't work for a few APIs which aren't
712 expecting bytes, but are already expecting some other unit
715 The most common is L</guestfs_lvcreate>. The guestfish command:
719 does not do what you might expect. Instead because
720 L</guestfs_lvcreate> is already expecting megabytes, this tries to
721 create a 100 I<terabyte> (100 megabytes * megabytes) logical volume.
722 The error message you get from this is also a little obscure.
724 This could be fixed in the generator by specially marking parameters
725 and return values which take bytes or other units.
727 =item Protocol should return errno with error messages.
729 It would be a nice-to-have to be able to get the original value of
730 'errno' from inside the appliance along error paths (where set).
731 Currently L<guestmount(1)> goes through hoops to try to reverse the
732 error message string into an errno, see the function error() in
737 =head2 PROTOCOL LIMITS
739 Internally libguestfs uses a message-based protocol to pass API calls
740 and their responses to and from a small "appliance" (see L</INTERNALS>
741 for plenty more detail about this). The maximum message size used by
742 the protocol is slightly less than 4 MB. For some API calls you may
743 need to be aware of this limit. The API calls which may be affected
744 are individually documented, with a link back to this section of the
747 A simple call such as L</guestfs_cat> returns its result (the file
748 data) in a simple string. Because this string is at some point
749 internally encoded as a message, the maximum size that it can return
750 is slightly under 4 MB. If the requested file is larger than this
751 then you will get an error.
753 In order to transfer large files into and out of the guest filesystem,
754 you need to use particular calls that support this. The sections
755 L</UPLOADING> and L</DOWNLOADING> document how to do this.
757 You might also consider mounting the disk image using our FUSE
758 filesystem support (L<guestmount(1)>).
760 =head2 KEYS AND PASSPHRASES
762 Certain libguestfs calls take a parameter that contains sensitive key
763 material, passed in as a C string.
765 In the future we would hope to change the libguestfs implementation so
766 that keys are L<mlock(2)>-ed into physical RAM, and thus can never end
767 up in swap. However this is I<not> done at the moment, because of the
768 complexity of such an implementation.
770 Therefore you should be aware that any key parameter you pass to
771 libguestfs might end up being written out to the swap partition. If
772 this is a concern, scrub the swap partition or don't use libguestfs on
775 =head1 CONNECTION MANAGEMENT
779 C<guestfs_h> is the opaque type representing a connection handle.
780 Create a handle by calling L</guestfs_create>. Call L</guestfs_close>
781 to free the handle and release all resources used.
783 For information on using multiple handles and threads, see the section
784 L</MULTIPLE HANDLES AND MULTIPLE THREADS> below.
786 =head2 guestfs_create
788 guestfs_h *guestfs_create (void);
790 Create a connection handle.
792 You have to call L</guestfs_add_drive> on the handle at least once.
794 This function returns a non-NULL pointer to a handle on success or
797 After configuring the handle, you have to call L</guestfs_launch>.
799 You may also want to configure error handling for the handle. See
800 L</ERROR HANDLING> section below.
804 void guestfs_close (guestfs_h *g);
806 This closes the connection handle and frees up all resources used.
808 =head1 ERROR HANDLING
810 The convention in all functions that return C<int> is that they return
811 C<-1> to indicate an error. You can get additional information on
812 errors by calling L</guestfs_last_error> and/or by setting up an error
813 handler with L</guestfs_set_error_handler>.
815 The default error handler prints the information string to C<stderr>.
817 Out of memory errors are handled differently. The default action is
818 to call L<abort(3)>. If this is undesirable, then you can set a
819 handler using L</guestfs_set_out_of_memory_handler>.
821 =head2 guestfs_last_error
823 const char *guestfs_last_error (guestfs_h *g);
825 This returns the last error message that happened on C<g>. If
826 there has not been an error since the handle was created, then this
829 The lifetime of the returned string is until the next error occurs, or
830 L</guestfs_close> is called.
832 The error string is not localized (ie. is always in English), because
833 this makes searching for error messages in search engines give the
834 largest number of results.
836 =head2 guestfs_set_error_handler
838 typedef void (*guestfs_error_handler_cb) (guestfs_h *g,
841 void guestfs_set_error_handler (guestfs_h *g,
842 guestfs_error_handler_cb cb,
845 The callback C<cb> will be called if there is an error. The
846 parameters passed to the callback are an opaque data pointer and the
847 error message string.
849 Note that the message string C<msg> is freed as soon as the callback
850 function returns, so if you want to stash it somewhere you must make
853 The default handler prints messages on C<stderr>.
855 If you set C<cb> to C<NULL> then I<no> handler is called.
857 =head2 guestfs_get_error_handler
859 guestfs_error_handler_cb guestfs_get_error_handler (guestfs_h *g,
862 Returns the current error handler callback.
864 =head2 guestfs_set_out_of_memory_handler
866 typedef void (*guestfs_abort_cb) (void);
867 int guestfs_set_out_of_memory_handler (guestfs_h *g,
870 The callback C<cb> will be called if there is an out of memory
871 situation. I<Note this callback must not return>.
873 The default is to call L<abort(3)>.
875 You cannot set C<cb> to C<NULL>. You can't ignore out of memory
878 =head2 guestfs_get_out_of_memory_handler
880 guestfs_abort_fn guestfs_get_out_of_memory_handler (guestfs_h *g);
882 This returns the current out of memory handler.
886 Libguestfs needs a kernel and initrd.img, which it finds by looking
887 along an internal path.
889 By default it looks for these in the directory C<$libdir/guestfs>
890 (eg. C</usr/local/lib/guestfs> or C</usr/lib64/guestfs>).
892 Use L</guestfs_set_path> or set the environment variable
893 L</LIBGUESTFS_PATH> to change the directories that libguestfs will
894 search in. The value is a colon-separated list of paths. The current
895 directory is I<not> searched unless the path contains an empty element
896 or C<.>. For example C<LIBGUESTFS_PATH=:/usr/lib/guestfs> would
897 search the current directory and then C</usr/lib/guestfs>.
899 =head1 HIGH-LEVEL API ACTIONS
903 We guarantee the libguestfs ABI (binary interface), for public,
904 high-level actions as outlined in this section. Although we will
905 deprecate some actions, for example if they get replaced by newer
906 calls, we will keep the old actions forever. This allows you the
907 developer to program in confidence against the libguestfs API.
917 =head2 GROUPS OF FUNCTIONALITY IN THE APPLIANCE
919 Using L</guestfs_available> you can test availability of
920 the following groups of functions. This test queries the
921 appliance to see if the appliance you are currently using
922 supports the functionality.
926 =head2 GUESTFISH supported COMMAND
928 In L<guestfish(3)> there is a handy interactive command
929 C<supported> which prints out the available groups and
930 whether they are supported by this build of libguestfs.
931 Note however that you have to do C<run> first.
933 =head2 SINGLE CALLS AT COMPILE TIME
935 If you need to test whether a single libguestfs function is
936 available at compile time, we recommend using build tools
937 such as autoconf or cmake. For example in autotools you could
940 AC_CHECK_LIB([guestfs],[guestfs_create])
941 AC_CHECK_FUNCS([guestfs_dd])
943 which would result in C<HAVE_GUESTFS_DD> being either defined
944 or not defined in your program.
946 =head2 SINGLE CALLS AT RUN TIME
948 Testing at compile time doesn't guarantee that a function really
949 exists in the library. The reason is that you might be dynamically
950 linked against a previous I<libguestfs.so> (dynamic library)
951 which doesn't have the call. This situation unfortunately results
952 in a segmentation fault, which is a shortcoming of the C dynamic
953 linking system itself.
955 You can use L<dlopen(3)> to test if a function is available
956 at run time, as in this example program (note that you still
957 need the compile time check as well):
969 #ifdef HAVE_GUESTFS_DD
973 /* Test if the function guestfs_dd is really available. */
974 dl = dlopen (NULL, RTLD_LAZY);
976 fprintf (stderr, "dlopen: %s\n", dlerror ());
979 has_function = dlsym (dl, "guestfs_dd") != NULL;
983 printf ("this libguestfs.so does NOT have guestfs_dd function\n");
985 printf ("this libguestfs.so has guestfs_dd function\n");
986 /* Now it's safe to call
987 guestfs_dd (g, "foo", "bar");
991 printf ("guestfs_dd function was not found at compile time\n");
995 You may think the above is an awful lot of hassle, and it is.
996 There are other ways outside of the C linking system to ensure
997 that this kind of incompatibility never arises, such as using
1000 Requires: libguestfs >= 1.0.80
1004 <!-- old anchor for the next section -->
1005 <a name="state_machine_and_low_level_event_api"/>
1011 Internally, libguestfs is implemented by running an appliance (a
1012 special type of small virtual machine) using L<qemu(1)>. Qemu runs as
1013 a child process of the main program.
1019 | | child process / appliance
1020 | | __________________________
1022 +-------------------+ RPC | +-----------------+ |
1023 | libguestfs <--------------------> guestfsd | |
1024 | | | +-----------------+ |
1025 \___________________/ | | Linux kernel | |
1026 | +--^--------------+ |
1027 \_________|________________/
1035 The library, linked to the main program, creates the child process and
1036 hence the appliance in the L</guestfs_launch> function.
1038 Inside the appliance is a Linux kernel and a complete stack of
1039 userspace tools (such as LVM and ext2 programs) and a small
1040 controlling daemon called L</guestfsd>. The library talks to
1041 L</guestfsd> using remote procedure calls (RPC). There is a mostly
1042 one-to-one correspondence between libguestfs API calls and RPC calls
1043 to the daemon. Lastly the disk image(s) are attached to the qemu
1044 process which translates device access by the appliance's Linux kernel
1045 into accesses to the image.
1047 A common misunderstanding is that the appliance "is" the virtual
1048 machine. Although the disk image you are attached to might also be
1049 used by some virtual machine, libguestfs doesn't know or care about
1050 this. (But you will care if both libguestfs's qemu process and your
1051 virtual machine are trying to update the disk image at the same time,
1052 since these usually results in massive disk corruption).
1054 =head1 STATE MACHINE
1056 libguestfs uses a state machine to model the child process:
1067 / | \ \ guestfs_launch
1078 \______/ <------ \________/
1080 The normal transitions are (1) CONFIG (when the handle is created, but
1081 there is no child process), (2) LAUNCHING (when the child process is
1082 booting up), (3) alternating between READY and BUSY as commands are
1083 issued to, and carried out by, the child process.
1085 The guest may be killed by L</guestfs_kill_subprocess>, or may die
1086 asynchronously at any time (eg. due to some internal error), and that
1087 causes the state to transition back to CONFIG.
1089 Configuration commands for qemu such as L</guestfs_add_drive> can only
1090 be issued when in the CONFIG state.
1092 The high-level API offers two calls that go from CONFIG through
1093 LAUNCHING to READY. L</guestfs_launch> blocks until the child process
1094 is READY to accept commands (or until some failure or timeout).
1095 L</guestfs_launch> internally moves the state from CONFIG to LAUNCHING
1096 while it is running.
1098 High-level API actions such as L</guestfs_mount> can only be issued
1099 when in the READY state. These high-level API calls block waiting for
1100 the command to be carried out (ie. the state to transition to BUSY and
1101 then back to READY). But using the low-level event API, you get
1102 non-blocking versions. (But you can still only carry out one
1103 operation per handle at a time - that is a limitation of the
1104 communications protocol we use).
1106 Finally, the child process sends asynchronous messages back to the
1107 main program, such as kernel log messages. Mostly these are ignored
1108 by the high-level API, but using the low-level event API you can
1109 register to receive these messages.
1111 =head2 SETTING CALLBACKS TO HANDLE EVENTS
1113 The child process generates events in some situations. Current events
1114 include: receiving a log message, the child process exits.
1116 Use the C<guestfs_set_*_callback> functions to set a callback for
1117 different types of events.
1119 Only I<one callback of each type> can be registered for each handle.
1120 Calling C<guestfs_set_*_callback> again overwrites the previous
1121 callback of that type. Cancel all callbacks of this type by calling
1122 this function with C<cb> set to C<NULL>.
1124 =head2 guestfs_set_log_message_callback
1126 typedef void (*guestfs_log_message_cb) (guestfs_h *g, void *opaque,
1127 char *buf, int len);
1128 void guestfs_set_log_message_callback (guestfs_h *g,
1129 guestfs_log_message_cb cb,
1132 The callback function C<cb> will be called whenever qemu or the guest
1133 writes anything to the console.
1135 Use this function to capture kernel messages and similar.
1137 Normally there is no log message handler, and log messages are just
1140 =head2 guestfs_set_subprocess_quit_callback
1142 typedef void (*guestfs_subprocess_quit_cb) (guestfs_h *g, void *opaque);
1143 void guestfs_set_subprocess_quit_callback (guestfs_h *g,
1144 guestfs_subprocess_quit_cb cb,
1147 The callback function C<cb> will be called when the child process
1148 quits, either asynchronously or if killed by
1149 L</guestfs_kill_subprocess>. (This corresponds to a transition from
1150 any state to the CONFIG state).
1152 =head2 guestfs_set_launch_done_callback
1154 typedef void (*guestfs_launch_done_cb) (guestfs_h *g, void *opaque);
1155 void guestfs_set_launch_done_callback (guestfs_h *g,
1156 guestfs_launch_done_cb cb,
1159 The callback function C<cb> will be called when the child process
1160 becomes ready first time after it has been launched. (This
1161 corresponds to a transition from LAUNCHING to the READY state).
1163 =head2 guestfs_set_close_callback
1165 typedef void (*guestfs_close_cb) (guestfs_h *g, void *opaque);
1166 void guestfs_set_close_callback (guestfs_h *g,
1167 guestfs_close_cb cb,
1170 The callback function C<cb> will be called while the handle
1171 is being closed (synchronously from L</guestfs_close>).
1173 Note that libguestfs installs an L<atexit(3)> handler to try to
1174 clean up handles that are open when the program exits. This
1175 means that this callback might be called indirectly from
1176 L<exit(3)>, which can cause unexpected problems in higher-level
1177 languages (eg. if your HLL interpreter has already been cleaned
1178 up by the time this is called, and if your callback then jumps
1179 into some HLL function).
1181 =head1 BLOCK DEVICE NAMING
1183 In the kernel there is now quite a profusion of schemata for naming
1184 block devices (in this context, by I<block device> I mean a physical
1185 or virtual hard drive). The original Linux IDE driver used names
1186 starting with C</dev/hd*>. SCSI devices have historically used a
1187 different naming scheme, C</dev/sd*>. When the Linux kernel I<libata>
1188 driver became a popular replacement for the old IDE driver
1189 (particularly for SATA devices) those devices also used the
1190 C</dev/sd*> scheme. Additionally we now have virtual machines with
1191 paravirtualized drivers. This has created several different naming
1192 systems, such as C</dev/vd*> for virtio disks and C</dev/xvd*> for Xen
1195 As discussed above, libguestfs uses a qemu appliance running an
1196 embedded Linux kernel to access block devices. We can run a variety
1197 of appliances based on a variety of Linux kernels.
1199 This causes a problem for libguestfs because many API calls use device
1200 or partition names. Working scripts and the recipe (example) scripts
1201 that we make available over the internet could fail if the naming
1204 Therefore libguestfs defines C</dev/sd*> as the I<standard naming
1205 scheme>. Internally C</dev/sd*> names are translated, if necessary,
1206 to other names as required. For example, under RHEL 5 which uses the
1207 C</dev/hd*> scheme, any device parameter C</dev/sda2> is translated to
1208 C</dev/hda2> transparently.
1210 Note that this I<only> applies to parameters. The
1211 L</guestfs_list_devices>, L</guestfs_list_partitions> and similar calls
1212 return the true names of the devices and partitions as known to the
1215 =head2 ALGORITHM FOR BLOCK DEVICE NAME TRANSLATION
1217 Usually this translation is transparent. However in some (very rare)
1218 cases you may need to know the exact algorithm. Such cases include
1219 where you use L</guestfs_config> to add a mixture of virtio and IDE
1220 devices to the qemu-based appliance, so have a mixture of C</dev/sd*>
1221 and C</dev/vd*> devices.
1223 The algorithm is applied only to I<parameters> which are known to be
1224 either device or partition names. Return values from functions such
1225 as L</guestfs_list_devices> are never changed.
1231 Is the string a parameter which is a device or partition name?
1235 Does the string begin with C</dev/sd>?
1239 Does the named device exist? If so, we use that device.
1240 However if I<not> then we continue with this algorithm.
1244 Replace initial C</dev/sd> string with C</dev/hd>.
1246 For example, change C</dev/sda2> to C</dev/hda2>.
1248 If that named device exists, use it. If not, continue.
1252 Replace initial C</dev/sd> string with C</dev/vd>.
1254 If that named device exists, use it. If not, return an error.
1258 =head2 PORTABILITY CONCERNS
1260 Although the standard naming scheme and automatic translation is
1261 useful for simple programs and guestfish scripts, for larger programs
1262 it is best not to rely on this mechanism.
1264 Where possible for maximum future portability programs using
1265 libguestfs should use these future-proof techniques:
1271 Use L</guestfs_list_devices> or L</guestfs_list_partitions> to list
1272 actual device names, and then use those names directly.
1274 Since those device names exist by definition, they will never be
1279 Use higher level ways to identify filesystems, such as LVM names,
1280 UUIDs and filesystem labels.
1286 =head2 COMMUNICATION PROTOCOL
1288 Don't rely on using this protocol directly. This section documents
1289 how it currently works, but it may change at any time.
1291 The protocol used to talk between the library and the daemon running
1292 inside the qemu virtual machine is a simple RPC mechanism built on top
1293 of XDR (RFC 1014, RFC 1832, RFC 4506).
1295 The detailed format of structures is in C<src/guestfs_protocol.x>
1296 (note: this file is automatically generated).
1298 There are two broad cases, ordinary functions that don't have any
1299 C<FileIn> and C<FileOut> parameters, which are handled with very
1300 simple request/reply messages. Then there are functions that have any
1301 C<FileIn> or C<FileOut> parameters, which use the same request and
1302 reply messages, but they may also be followed by files sent using a
1305 =head3 ORDINARY FUNCTIONS (NO FILEIN/FILEOUT PARAMS)
1307 For ordinary functions, the request message is:
1309 total length (header + arguments,
1310 but not including the length word itself)
1311 struct guestfs_message_header (encoded as XDR)
1312 struct guestfs_<foo>_args (encoded as XDR)
1314 The total length field allows the daemon to allocate a fixed size
1315 buffer into which it slurps the rest of the message. As a result, the
1316 total length is limited to C<GUESTFS_MESSAGE_MAX> bytes (currently
1317 4MB), which means the effective size of any request is limited to
1318 somewhere under this size.
1320 Note also that many functions don't take any arguments, in which case
1321 the C<guestfs_I<foo>_args> is completely omitted.
1323 The header contains the procedure number (C<guestfs_proc>) which is
1324 how the receiver knows what type of args structure to expect, or none
1327 The reply message for ordinary functions is:
1329 total length (header + ret,
1330 but not including the length word itself)
1331 struct guestfs_message_header (encoded as XDR)
1332 struct guestfs_<foo>_ret (encoded as XDR)
1334 As above the C<guestfs_I<foo>_ret> structure may be completely omitted
1335 for functions that return no formal return values.
1337 As above the total length of the reply is limited to
1338 C<GUESTFS_MESSAGE_MAX>.
1340 In the case of an error, a flag is set in the header, and the reply
1341 message is slightly changed:
1343 total length (header + error,
1344 but not including the length word itself)
1345 struct guestfs_message_header (encoded as XDR)
1346 struct guestfs_message_error (encoded as XDR)
1348 The C<guestfs_message_error> structure contains the error message as a
1351 =head3 FUNCTIONS THAT HAVE FILEIN PARAMETERS
1353 A C<FileIn> parameter indicates that we transfer a file I<into> the
1354 guest. The normal request message is sent (see above). However this
1355 is followed by a sequence of file chunks.
1357 total length (header + arguments,
1358 but not including the length word itself,
1359 and not including the chunks)
1360 struct guestfs_message_header (encoded as XDR)
1361 struct guestfs_<foo>_args (encoded as XDR)
1362 sequence of chunks for FileIn param #0
1363 sequence of chunks for FileIn param #1 etc.
1365 The "sequence of chunks" is:
1367 length of chunk (not including length word itself)
1368 struct guestfs_chunk (encoded as XDR)
1370 struct guestfs_chunk (encoded as XDR)
1373 struct guestfs_chunk (with data.data_len == 0)
1375 The final chunk has the C<data_len> field set to zero. Additionally a
1376 flag is set in the final chunk to indicate either successful
1377 completion or early cancellation.
1379 At time of writing there are no functions that have more than one
1380 FileIn parameter. However this is (theoretically) supported, by
1381 sending the sequence of chunks for each FileIn parameter one after
1382 another (from left to right).
1384 Both the library (sender) I<and> the daemon (receiver) may cancel the
1385 transfer. The library does this by sending a chunk with a special
1386 flag set to indicate cancellation. When the daemon sees this, it
1387 cancels the whole RPC, does I<not> send any reply, and goes back to
1388 reading the next request.
1390 The daemon may also cancel. It does this by writing a special word
1391 C<GUESTFS_CANCEL_FLAG> to the socket. The library listens for this
1392 during the transfer, and if it gets it, it will cancel the transfer
1393 (it sends a cancel chunk). The special word is chosen so that even if
1394 cancellation happens right at the end of the transfer (after the
1395 library has finished writing and has started listening for the reply),
1396 the "spurious" cancel flag will not be confused with the reply
1399 This protocol allows the transfer of arbitrary sized files (no 32 bit
1400 limit), and also files where the size is not known in advance
1401 (eg. from pipes or sockets). However the chunks are rather small
1402 (C<GUESTFS_MAX_CHUNK_SIZE>), so that neither the library nor the
1403 daemon need to keep much in memory.
1405 =head3 FUNCTIONS THAT HAVE FILEOUT PARAMETERS
1407 The protocol for FileOut parameters is exactly the same as for FileIn
1408 parameters, but with the roles of daemon and library reversed.
1410 total length (header + ret,
1411 but not including the length word itself,
1412 and not including the chunks)
1413 struct guestfs_message_header (encoded as XDR)
1414 struct guestfs_<foo>_ret (encoded as XDR)
1415 sequence of chunks for FileOut param #0
1416 sequence of chunks for FileOut param #1 etc.
1418 =head3 INITIAL MESSAGE
1420 Because the underlying channel (QEmu -net channel) doesn't have any
1421 sort of connection control, when the daemon launches it sends an
1422 initial word (C<GUESTFS_LAUNCH_FLAG>) which indicates that the guest
1423 and daemon is alive. This is what L</guestfs_launch> waits for.
1425 =head1 MULTIPLE HANDLES AND MULTIPLE THREADS
1427 All high-level libguestfs actions are synchronous. If you want
1428 to use libguestfs asynchronously then you must create a thread.
1430 Only use the handle from a single thread. Either use the handle
1431 exclusively from one thread, or provide your own mutex so that two
1432 threads cannot issue calls on the same handle at the same time.
1434 =head1 QEMU WRAPPERS
1436 If you want to compile your own qemu, run qemu from a non-standard
1437 location, or pass extra arguments to qemu, then you can write a
1438 shell-script wrapper around qemu.
1440 There is one important rule to remember: you I<must C<exec qemu>> as
1441 the last command in the shell script (so that qemu replaces the shell
1442 and becomes the direct child of the libguestfs-using program). If you
1443 don't do this, then the qemu process won't be cleaned up correctly.
1445 Here is an example of a wrapper, where I have built my own copy of
1449 qemudir=/home/rjones/d/qemu
1450 exec $qemudir/x86_64-softmmu/qemu-system-x86_64 -L $qemudir/pc-bios "$@"
1452 Save this script as C</tmp/qemu.wrapper> (or wherever), C<chmod +x>,
1453 and then use it by setting the LIBGUESTFS_QEMU environment variable.
1456 LIBGUESTFS_QEMU=/tmp/qemu.wrapper guestfish
1458 Note that libguestfs also calls qemu with the -help and -version
1459 options in order to determine features.
1461 =head1 LIBGUESTFS VERSION NUMBERS
1463 Since April 2010, libguestfs has started to make separate development
1464 and stable releases, along with corresponding branches in our git
1465 repository. These separate releases can be identified by version
1468 even numbers for stable: 1.2.x, 1.4.x, ...
1469 .-------- odd numbers for development: 1.3.x, 1.5.x, ...
1475 | `-------- sub-version
1477 `------ always '1' because we don't change the ABI
1479 Thus "1.3.5" is the 5th update to the development branch "1.3".
1481 As time passes we cherry pick fixes from the development branch and
1482 backport those into the stable branch, the effect being that the
1483 stable branch should get more stable and less buggy over time. So the
1484 stable releases are ideal for people who don't need new features but
1485 would just like the software to work.
1487 Our criteria for backporting changes are:
1493 Documentation changes which don't affect any code are
1494 backported unless the documentation refers to a future feature
1495 which is not in stable.
1499 Bug fixes which are not controversial, fix obvious problems, and
1500 have been well tested are backported.
1504 Simple rearrangements of code which shouldn't affect how it works get
1505 backported. This is so that the code in the two branches doesn't get
1506 too far out of step, allowing us to backport future fixes more easily.
1510 We I<don't> backport new features, new APIs, new tools etc, except in
1511 one exceptional case: the new feature is required in order to
1512 implement an important bug fix.
1516 A new stable branch starts when we think the new features in
1517 development are substantial and compelling enough over the current
1518 stable branch to warrant it. When that happens we create new stable
1519 and development versions 1.N.0 and 1.(N+1).0 [N is even]. The new
1520 dot-oh release won't necessarily be so stable at this point, but by
1521 backporting fixes from development, that branch will stabilize over
1524 =head1 ENVIRONMENT VARIABLES
1528 =item LIBGUESTFS_APPEND
1530 Pass additional options to the guest kernel.
1532 =item LIBGUESTFS_DEBUG
1534 Set C<LIBGUESTFS_DEBUG=1> to enable verbose messages. This
1535 has the same effect as calling C<guestfs_set_verbose (g, 1)>.
1537 =item LIBGUESTFS_MEMSIZE
1539 Set the memory allocated to the qemu process, in megabytes. For
1542 LIBGUESTFS_MEMSIZE=700
1544 =item LIBGUESTFS_PATH
1546 Set the path that libguestfs uses to search for kernel and initrd.img.
1547 See the discussion of paths in section PATH above.
1549 =item LIBGUESTFS_QEMU
1551 Set the default qemu binary that libguestfs uses. If not set, then
1552 the qemu which was found at compile time by the configure script is
1555 See also L</QEMU WRAPPERS> above.
1557 =item LIBGUESTFS_TRACE
1559 Set C<LIBGUESTFS_TRACE=1> to enable command traces. This
1560 has the same effect as calling C<guestfs_set_trace (g, 1)>.
1564 Location of temporary directory, defaults to C</tmp>.
1566 If libguestfs was compiled to use the supermin appliance then each
1567 handle will require rather a large amount of space in this directory
1568 for short periods of time (~ 80 MB). You can use C<$TMPDIR> to
1569 configure another directory to use in case C</tmp> is not large
1581 L<virt-inspector(1)>,
1582 L<virt-list-filesystems(1)>,
1583 L<virt-list-partitions(1)>,
1592 L<http://libguestfs.org/>.
1594 Tools with a similar purpose:
1603 To get a list of bugs against libguestfs use this link:
1605 L<https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools>
1607 To report a new bug against libguestfs use this link:
1609 L<https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools>
1611 When reporting a bug, please check:
1617 That the bug hasn't been reported already.
1621 That you are testing a recent version.
1625 Describe the bug accurately, and give a way to reproduce it.
1629 Run libguestfs-test-tool and paste the B<complete, unedited>
1630 output into the bug report.
1636 Richard W.M. Jones (C<rjones at redhat dot com>)
1640 Copyright (C) 2009-2010 Red Hat Inc.
1641 L<http://libguestfs.org/>
1643 This library is free software; you can redistribute it and/or
1644 modify it under the terms of the GNU Lesser General Public
1645 License as published by the Free Software Foundation; either
1646 version 2 of the License, or (at your option) any later version.
1648 This library is distributed in the hope that it will be useful,
1649 but WITHOUT ANY WARRANTY; without even the implied warranty of
1650 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
1651 Lesser General Public License for more details.
1653 You should have received a copy of the GNU Lesser General Public
1654 License along with this library; if not, write to the Free Software
1655 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA