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)
52 - libmagic (the library that corresponds to the 'file' command)
60 - Augeas (http://augeas.net/)
62 - squashfs-tools (mksquashfs only)
64 - genisoimage / mkisofs
66 - hivex >= 1.2.1 (http://libguestfs.org/download)
68 - (Optional) FUSE to build the FUSE module
70 - perldoc (pod2man, pod2text) to generate the manual pages and
73 - (Optional) Readline to have nicer command-line editing in guestfish.
75 - (Optional) xmllint to validate virt-inspector RELAX NG schema
77 - (Optional) OCaml + OCaml library xml-light if you want to rebuild
78 the generated files, and also to build the OCaml bindings
79 (http://tech.motion-twin.com/xmllight.html)
81 - (Optional) local Fedora mirror
83 - (Optional) Perl if you want to build the perl bindings
85 - (Optional) Python if you want to build the python bindings
87 - (Optional) Ruby, rake if you want to build the ruby bindings
89 - (Optional) Java, JNI, jpackage-utils if you want to build the java
92 - (Optional) GHC if you want to build the Haskell bindings
94 - (Optional) Perl XML::XPath, Sys::Virt modules (for libvirt support
97 - (Optional, but highly recommended) perl-libintl for translating perl code.
99 - (Optional) po4a for translating manpages and POD files.
101 - (Optional) PHP, phpize if you want to build the PHP bindings
103 Running ./configure will check you have all the requirements installed
108 ----------------------------------------------------------------------
110 Then make the daemon, library and root filesystem:
112 ./configure [--with-mirror=URI]
115 Use the optional --with-mirror parameter to specify the URI of a local
116 Fedora mirror. See the discussion of the MIRROR parameter in the
117 febootstrap(8) manpage.
119 Finally run the tests:
123 If everything works, you can install the library and tools by running
124 this command as root:
130 ----------------------------------------------------------------------
132 We provide packages for Fedora >= 11 in Fedora. Use those, or build
133 from our source RPMs - it's far simpler that way.
135 You can compile libguestfs on Fedora 10 but you cannot use it with the
136 version of qemu in Fedora 10. You need to compile your own qemu, see
137 section 'qemu' below.
140 RHEL / EPEL / CentOS etc
141 ----------------------------------------------------------------------
143 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
144 or build from our source RPMs.
148 ----------------------------------------------------------------------
150 libguestfs is now built as a package in Debian by Guido Gunther and
151 the other Debian libvirt maintainers. See:
153 http://wiki.debian.org/Teams/DebianLibvirtTeam#Packages
155 You can build for Debian in two different ways, either building a
156 Fedora-based appliance using febootstrap, yum, rpm, fakeroot,
157 fakechroot (all packaged in Debian). However the recommended way is
158 to build a Debian-based appliance using debootstrap and debirf.
160 Both ways are supported by the configure script.
164 ----------------------------------------------------------------------
166 By far the most common problem is with broken or incompatible
169 Different versions of qemu have problems booting the appliance for
170 different reasons. This varies between versions of qemu, and Linux
171 distributions which add their own patches.
173 If you find a problem, you could try using your own qemu built from
174 source (qemu is very easy to build from source), with a 'qemu
175 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
179 ----------------------------------------------------------------------
181 By default the configure script will look for qemu-kvm (KVM support).
182 You will need a reasonably recent processor for this to work. KVM is
183 much faster than using plain Qemu.
185 You may also need to enable KVM support for non-root users, by following
188 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
190 On some systems, this will work too:
194 On some systems, the chmod will not survive a reboot, and you will
195 need to make edits to the udev configuration.
199 ----------------------------------------------------------------------
201 Previous versions of libguestfs required something called "vmchannel".
202 Vmchannel is a special device given to virtual machines which allows
203 them to communicate in some way with the host, often (but not always)
204 without using a traditional network device. In reality, there is no
205 one thing called "vmchannel". This idea has been reimplemented
206 several times under the name vmchannel, and other hypervisors have
207 their own incompatible implementation(s) too.
209 In libguestfs <= 1.0.71, we required a specific vmchannel which is
210 properly known as "guestfwd" and has been upstream in qemu since here:
212 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
214 In libguestfs >= 1.0.71 we don't require any vmchannel implementation,
215 as long as qemu has been compiled with support for SLIRP (user mode
216 networking, or "-net user"), which is almost always the case.
218 In libguestfs >= 1.5.4 we switched again to using qemu's virtio-serial
219 and removed all the other vmchannels and the SLIRP channel.
223 ----------------------------------------------------------------------
225 If you configure with --enable-supermin then we will build a supermin
226 appliance (supermin = super-minimized). This is a very specialized
227 appliance which is built on-the-fly at runtime (specifically, when you
228 call guestfs_launch).
230 The normal appliance is a self-contained Linux operating system, based
231 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
232 copy of all the libraries and programs needed, like kernel, libc,
233 bash, coreutils etc etc.
235 The supermin appliance removes the kernel and all the executable
236 libraries and programs from the appliance. That just leaves a
237 skeleton of config files and some data files, which is obviously
238 massively smaller than the normal appliance. At runtime we rebuild
239 the appliance on-the-fly from the libraries and programs on the host
240 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
242 Although this process of rebuilding the appliance each time sounds
243 slow, it turns out to be faster than using the prebuilt appliance.
244 (Most of the saving comes from not compressing the appliance - it
245 transpires that decompressing the appliance is the slowest part of the
246 whole boot sequence). On my machine, a new appliance can be built in
247 under a fifth of a second, and the boot time is several seconds
250 The big advantage of the supermin appliance for distributions like
251 Fedora is that it gets security fixes automatically from the host, so
252 there is no need to rebuild the whole of libguestfs for a security
253 update in some underlying library.
255 There are several DISADVANTAGES:
257 It won't work at all except in very narrow, controlled cases like the
258 Fedora packaging case. We control the dependencies of the libguestfs
259 RPM tightly to ensure that the required binaries are actually present
262 Furthermore there are certain unlikely changes in the packages on the
263 host which could break a supermin appliance, eg. an updated library
264 which depends on an additional data file.
266 Also supermin appliances are subjected to changes in the host kernel
267 which might break compatibility with qemu -- these are, of course,
268 real bugs in any case.
270 Lastly, supermin appliances really can't be moved between branches of
271 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
272 they are not self-contained and they rely on certain libraries being
273 around. You shouldn't do this anyway.
275 Use supermin appliances with caution.
278 Notes on cross-architecture support
279 ----------------------------------------------------------------------
281 At the moment we basically don't support cross-architecture or
282 32-on-64. This limits what is possible for some guests. Filesystem
283 operations and FUSE will work fine, but running commands in guests may
286 To enable this requires work for cross-architecture and 32-on-64
287 support in febootstrap, fakeroot and fakechroot.
289 The daemon/ directory contains its own configure script. This is so
290 that in future we will be able to cross-compile the daemon.
294 ----------------------------------------------------------------------
296 On my machines I can usually rebuild the appliance in around 3
297 minutes. If it takes much longer for you, use a local Fedora mirror
300 To use squid to cache yum downloads, read this first:
301 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
302 (In brief, because yum chooses random mirrors each time, squid doesn't
303 work very well with default yum configuration. To get around this,
304 choose a Fedora mirror which is close to you, set this with
305 './configure --with-mirror=[...]', and then proxy the whole lot
306 through squid by setting http_proxy environment variable).
308 You will also need to substantially increase the squid configuration
310 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
313 Porting to other Linux distros / non-Linux
314 ----------------------------------------------------------------------
316 libguestfs itself should be fairly portable to other Linux
317 distributions. Non-Linux ports are trickier, but we will accept
318 patches if they aren't too invasive.
320 The main porting issues are with the dependencies needed to build the
321 appliance. You will need to find or port the following packages
327 - rpm-python http://www.rpm.org/
328 - yum http://yum.baseurl.org/
329 - febootstrap http://people.redhat.com/~rjones/febootstrap/
332 Copyright and license information
333 ----------------------------------------------------------------------
335 Copyright (C) 2009-2010 Red Hat Inc.
337 The library is distributed under the LGPLv2+. The programs are
338 distributed under the GPLv2+. Please see the files COPYING and
339 COPYING.LIB for full license information.