1 Libguestfs is a library for accessing and modifying guest disk images.
2 Amongst the things this is good for: making batch configuration
3 changes to guests, getting disk used/free statistics (see also:
4 virt-df), migrating between virtualization systems (see also:
5 virt-p2v), performing partial backups, performing partial guest
6 clones, cloning guests and changing registry/UUID/hostname info, and
9 Libguestfs uses Linux kernel and qemu code, and can access any type of
10 guest filesystem that Linux and qemu can, including but not limited
11 to: ext2/3/4, btrfs, FAT and NTFS, LVM, many different disk partition
12 schemes, qcow, qcow2, vmdk.
14 Libguestfs provides ways to enumerate guest storage (eg. partitions,
15 LVs, what filesystem is in each LV, etc.). It can also run commands
16 in the context of the guest. Also you can access filesystems over
19 Libguestfs is a library that can be linked with C and C++ management
20 programs (or management programs written in OCaml, Perl, Python, Ruby,
21 Java, PHP, Haskell or C#). You can also use it from shell scripts or the
24 Libguestfs was written by Richard W.M. Jones (rjones@redhat.com) and
25 hacked on by lots of other people. For discussion, development,
26 patches, etc. please use the mailing list:
28 http://www.redhat.com/mailman/listinfo/libguestfs
32 ----------------------------------------------------------------------
34 http://libguestfs.org/
38 ----------------------------------------------------------------------
40 - recent QEMU >= 0.12 with virtio-serial support
48 - XDR, rpcgen (on Linux these are provided by glibc)
50 - pcre (Perl Compatible Regular Expressions C library) (optional)
52 - libmagic (the library that corresponds to the 'file' command) (optional)
58 - Augeas (http://augeas.net/) (optional)
62 - squashfs-tools (mksquashfs only)
64 - genisoimage / mkisofs
66 - hivex >= 1.2.1 (http://libguestfs.org/download)
68 - (Optional) Berkeley DB 'db_dump' and 'db_load' utilities
69 (db4-utils or db4.X-util or similar)
71 - (Optional) FUSE to build the FUSE module
73 - perldoc (pod2man, pod2text, pod2html) to generate the manual pages
74 and other documentation.
76 - (Optional) Readline to have nicer command-line editing in guestfish.
78 - (Optional) xmllint to validate virt-inspector RELAX NG schema
80 - (Optional) OCaml if you want to rebuild the generated files, and
81 also to build the OCaml bindings
83 - (Optional) local Fedora mirror
85 - (Optional) Perl if you want to build the perl bindings
87 - (Optional) Python if you want to build the python bindings
89 - (Optional) Ruby, rake if you want to build the ruby bindings
91 - (Optional) Java, JNI, jpackage-utils if you want to build the java
94 - (Optional) GHC if you want to build the Haskell bindings
96 - (Optional) Perl Sys::Virt module.
98 - (Optional) Perl Win::Hivex module.
100 - (Optional) Perl Pod::Usage module.
102 - (Optional) Perl Test::More module (from perl Test::Simple).
104 - (Optional) Perl String::ShellQuote module.
106 - (Optional, but highly recommended) perl-libintl for translating perl code.
108 - (Optional) po4a for translating manpages and POD files.
110 - (Optional) PHP, phpize if you want to build the PHP bindings
112 Running ./configure will check you have all the requirements installed
117 ----------------------------------------------------------------------
119 Then make the daemon, library and root filesystem:
121 ./configure [--with-mirror=URI]
124 Use the optional --with-mirror parameter to specify the URI of a local
125 Fedora mirror. See the discussion of the MIRROR parameter in the
126 febootstrap(8) manpage.
128 Finally run the tests:
132 If everything works, you can install the library and tools by running
133 this command as root:
139 ----------------------------------------------------------------------
141 We provide packages for Fedora >= 11 in Fedora. Use those, or build
142 from our source RPMs - it's far simpler that way.
144 You can compile libguestfs on Fedora 10 but you cannot use it with the
145 version of qemu in Fedora 10. You need to compile your own qemu, see
146 section 'qemu' below.
149 RHEL / EPEL / CentOS etc
150 ----------------------------------------------------------------------
152 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
153 or build from our source RPMs.
157 ----------------------------------------------------------------------
159 libguestfs is now built as a package in Debian by Guido Gunther and
160 the other Debian libvirt maintainers. See:
162 http://wiki.debian.org/Teams/DebianLibvirtTeam#Packages
164 You can build for Debian in two different ways, either building a
165 Fedora-based appliance using febootstrap, yum, rpm, fakeroot,
166 fakechroot (all packaged in Debian). However the recommended way is
167 to build a Debian-based appliance using debootstrap and debirf.
169 Both ways are supported by the configure script.
173 ----------------------------------------------------------------------
175 By far the most common problem is with broken or incompatible
178 Different versions of qemu have problems booting the appliance for
179 different reasons. This varies between versions of qemu, and Linux
180 distributions which add their own patches.
182 If you find a problem, you could try using your own qemu built from
183 source (qemu is very easy to build from source), with a 'qemu
184 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
188 ----------------------------------------------------------------------
190 By default the configure script will look for qemu-kvm (KVM support).
191 You will need a reasonably recent processor for this to work. KVM is
192 much faster than using plain Qemu.
194 You may also need to enable KVM support for non-root users, by following
197 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
199 On some systems, this will work too:
203 On some systems, the chmod will not survive a reboot, and you will
204 need to make edits to the udev configuration.
208 ----------------------------------------------------------------------
210 Previous versions of libguestfs required something called "vmchannel".
211 Vmchannel is a special device given to virtual machines which allows
212 them to communicate in some way with the host, often (but not always)
213 without using a traditional network device. In reality, there is no
214 one thing called "vmchannel". This idea has been reimplemented
215 several times under the name vmchannel, and other hypervisors have
216 their own incompatible implementation(s) too.
218 In libguestfs <= 1.0.71, we required a specific vmchannel which is
219 properly known as "guestfwd" and has been upstream in qemu since here:
221 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
223 In libguestfs >= 1.0.71 we don't require any vmchannel implementation,
224 as long as qemu has been compiled with support for SLIRP (user mode
225 networking, or "-net user"), which is almost always the case.
227 In libguestfs >= 1.5.4 we switched again to using qemu's virtio-serial
228 and removed all the other vmchannels and the SLIRP channel.
232 ----------------------------------------------------------------------
234 If you configure with --enable-supermin then we will build a supermin
235 appliance (supermin = super-minimized). This is a very specialized
236 appliance which is built on-the-fly at runtime (specifically, when you
237 call guestfs_launch).
239 The normal appliance is a self-contained Linux operating system, based
240 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
241 copy of all the libraries and programs needed, like kernel, libc,
242 bash, coreutils etc etc.
244 The supermin appliance removes the kernel and all the executable
245 libraries and programs from the appliance. That just leaves a
246 skeleton of config files and some data files, which is obviously
247 massively smaller than the normal appliance. At runtime we rebuild
248 the appliance on-the-fly from the libraries and programs on the host
249 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
251 Although this process of rebuilding the appliance each time sounds
252 slow, it turns out to be faster than using the prebuilt appliance.
253 (Most of the saving comes from not compressing the appliance - it
254 transpires that decompressing the appliance is the slowest part of the
255 whole boot sequence). On my machine, a new appliance can be built in
256 under a fifth of a second, and the boot time is several seconds
259 The big advantage of the supermin appliance for distributions like
260 Fedora is that it gets security fixes automatically from the host, so
261 there is no need to rebuild the whole of libguestfs for a security
262 update in some underlying library.
264 There are several DISADVANTAGES:
266 It won't work at all except in very narrow, controlled cases like the
267 Fedora packaging case. We control the dependencies of the libguestfs
268 RPM tightly to ensure that the required binaries are actually present
271 Furthermore there are certain unlikely changes in the packages on the
272 host which could break a supermin appliance, eg. an updated library
273 which depends on an additional data file.
275 Also supermin appliances are subjected to changes in the host kernel
276 which might break compatibility with qemu -- these are, of course,
277 real bugs in any case.
279 Lastly, supermin appliances really can't be moved between branches of
280 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
281 they are not self-contained and they rely on certain libraries being
282 around. You shouldn't do this anyway.
284 Use supermin appliances with caution.
287 Notes on cross-architecture support
288 ----------------------------------------------------------------------
290 At the moment we basically don't support cross-architecture or
291 32-on-64. This limits what is possible for some guests. Filesystem
292 operations and FUSE will work fine, but running commands in guests may
295 To enable this requires work for cross-architecture and 32-on-64
296 support in febootstrap, fakeroot and fakechroot.
298 The daemon/ directory contains its own configure script. This is so
299 that in future we will be able to cross-compile the daemon.
303 ----------------------------------------------------------------------
305 On my machines I can usually rebuild the appliance in around 3
306 minutes. If it takes much longer for you, use a local Fedora mirror
309 To use squid to cache yum downloads, read this first:
310 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
311 (In brief, because yum chooses random mirrors each time, squid doesn't
312 work very well with default yum configuration. To get around this,
313 choose a Fedora mirror which is close to you, set this with
314 './configure --with-mirror=[...]', and then proxy the whole lot
315 through squid by setting http_proxy environment variable).
317 You will also need to substantially increase the squid configuration
319 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
322 Porting to other Linux distros / non-Linux
323 ----------------------------------------------------------------------
325 libguestfs itself should be fairly portable to other Linux
326 distributions. Non-Linux ports are trickier, but we will accept
327 patches if they aren't too invasive.
329 The main porting issues are with the dependencies needed to build the
330 appliance. You will need to find or port the following packages
336 - rpm-python http://www.rpm.org/
337 - yum http://yum.baseurl.org/
338 - febootstrap http://people.redhat.com/~rjones/febootstrap/
341 Copyright and license information
342 ----------------------------------------------------------------------
344 Copyright (C) 2009-2010 Red Hat Inc.
346 The library is distributed under the LGPLv2+. The programs are
347 distributed under the GPLv2+. Please see the files COPYING and
348 COPYING.LIB for full license information.