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, 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 >= 0.10 with vmchannel support
41 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
49 - XDR, rpcgen (on Linux these are provided by glibc)
51 - pcre (Perl Compatible Regular Expressions C library)
53 - libmagic (the library that corresponds to the 'file' command)
55 - squashfs-tools (mksquashfs only)
57 - genisoimage / mkisofs
59 - (Optional) hivex >= 1.2.1 to build Windows Registry support
61 - (Optional) FUSE to build the FUSE module
63 - (Optional) Augeas (http://augeas.net/)
65 - perldoc (pod2man, pod2text) to generate the manual pages and
68 - (Optional) Readline to have nicer command-line editing in guestfish.
70 - (Optional) xmllint to validate virt-inspector RELAX NG schema
72 - (Optional) OCaml + OCaml library xml-light if you want to rebuild
73 the generated files, and also to build the OCaml bindings
74 (http://tech.motion-twin.com/xmllight.html)
76 - (Optional) local Fedora mirror
78 - (Optional) Perl if you want to build the perl bindings
80 - (Optional) Python if you want to build the python bindings
82 - (Optional) Ruby, rake if you want to build the ruby bindings
84 - (Optional) Java, JNI, jpackage-utils if you want to build the java
87 - (Optional) GHC if you want to build the Haskell bindings
89 - (Optional) Perl XML::XPath, Sys::Virt modules (for libvirt support
92 - (Optional, but highly recommended) perl-libintl for translating perl code.
94 Running ./configure will check you have all the requirements installed
99 ----------------------------------------------------------------------
101 Then make the daemon, library and root filesystem:
103 ./configure [--with-mirror=URI]
106 Use the optional --with-mirror parameter to specify the URI of a local
107 Fedora mirror. See the discussion of the MIRROR parameter in the
108 febootstrap(8) manpage.
110 Finally run the tests:
114 If everything works, you can install the library and tools by running
115 this command as root:
121 ----------------------------------------------------------------------
123 We provide packages for Fedora >= 11 in Fedora. Use those, or build
124 from our source RPMs - it's far simpler that way.
126 You can compile libguestfs on Fedora 10 but you cannot use it with the
127 version of qemu in Fedora 10. You need to compile your own qemu, see
128 section 'qemu' below.
131 RHEL / EPEL / CentOS etc
132 ----------------------------------------------------------------------
134 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
135 or build from our source RPMs.
139 ----------------------------------------------------------------------
141 libguestfs is now built as a package in Debian by Guido Gunther and
142 the other Debian libvirt maintainers. See:
144 http://wiki.debian.org/Teams/DebianLibvirtTeam#Packages
146 You can build for Debian in two different ways, either building a
147 Fedora-based appliance using febootstrap, yum, rpm, fakeroot,
148 fakechroot (all packaged in Debian). However the recommended way is
149 to build a Debian-based appliance using debootstrap and debirf.
151 Both ways are supported by the configure script.
155 ----------------------------------------------------------------------
157 By far the most common problem is with broken or incompatible
160 Different versions of qemu have problems booting the appliance for
161 different reasons. This varies between versions of qemu, and Linux
162 distributions which add their own patches.
164 If you find a problem, you could try using your own qemu built from
165 source (qemu is very easy to build from source), with a 'qemu
166 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
170 ----------------------------------------------------------------------
172 By default the configure script will look for qemu-kvm (KVM support).
173 You will need a reasonably recent processor for this to work. KVM is
174 much faster than using plain Qemu.
176 You may also need to enable KVM support for non-root users, by following
179 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
181 On some systems, this will work too:
185 On some systems, the chmod will not survive a reboot, and you will
186 need to make edits to the udev configuration.
190 ----------------------------------------------------------------------
192 Previous versions of libguestfs required something called "vmchannel".
193 Vmchannel is a special device given to virtual machines which allows
194 them to communicate in some way with the host, often (but not always)
195 without using a traditional network device. In reality, there is no
196 one thing called "vmchannel". This idea has been reimplemented
197 several times under the name vmchannel, and other hypervisors have
198 their own incompatible implementation(s) too.
200 In libguestfs <= 1.0.71, we required a specific vmchannel which is
201 properly known as "guestfwd" and has been upstream in qemu since here:
203 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
205 In libguestfs >= 1.0.71 we don't require any vmchannel implementation,
206 as long as qemu has been compiled with support for SLIRP (user mode
207 networking, or "-net user"), which is almost always the case.
209 However we still offer the ability to use vmchannel, and in future we
210 may add support for other types of qemu, which is useful in a few
211 cases, specifically where qemu packagers decide to compile out support
212 for SLIRP (qemu packagers: please don't do this).
216 ----------------------------------------------------------------------
218 If you configure with --enable-supermin then we will build a supermin
219 appliance (supermin = super-minimized). This is a very specialized
220 appliance which is built on-the-fly at runtime (specifically, when you
221 call guestfs_launch).
223 The normal appliance is a self-contained Linux operating system, based
224 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
225 copy of all the libraries and programs needed, like kernel, libc,
226 bash, coreutils etc etc.
228 The supermin appliance removes the kernel and all the executable
229 libraries and programs from the appliance. That just leaves a
230 skeleton of config files and some data files, which is obviously
231 massively smaller than the normal appliance. At runtime we rebuild
232 the appliance on-the-fly from the libraries and programs on the host
233 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
235 Although this process of rebuilding the appliance each time sounds
236 slow, it turns out to be faster than using the prebuilt appliance.
237 (Most of the saving comes from not compressing the appliance - it
238 transpires that decompressing the appliance is the slowest part of the
239 whole boot sequence). On my machine, a new appliance can be built in
240 under a fifth of a second, and the boot time is several seconds
243 The big advantage of the supermin appliance for distributions like
244 Fedora is that it gets security fixes automatically from the host, so
245 there is no need to rebuild the whole of libguestfs for a security
246 update in some underlying library.
248 There are several DISADVANTAGES:
250 It won't work at all except in very narrow, controlled cases like the
251 Fedora packaging case. We control the dependencies of the libguestfs
252 RPM tightly to ensure that the required binaries are actually present
255 Furthermore there are certain unlikely changes in the packages on the
256 host which could break a supermin appliance, eg. an updated library
257 which depends on an additional data file.
259 Also supermin appliances are subjected to changes in the host kernel
260 which might break compatibility with qemu -- these are, of course,
261 real bugs in any case.
263 Lastly, supermin appliances really can't be moved between branches of
264 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
265 they are not self-contained and they rely on certain libraries being
266 around. You shouldn't do this anyway.
268 Use supermin appliances with caution.
271 Notes on cross-architecture support
272 ----------------------------------------------------------------------
274 At the moment we basically don't support cross-architecture or
275 32-on-64. This limits what is possible for some guests. Filesystem
276 operations and FUSE will work fine, but running commands in guests may
279 To enable this requires work for cross-architecture and 32-on-64
280 support in febootstrap, fakeroot and fakechroot.
282 The daemon/ directory contains its own configure script. This is so
283 that in future we will be able to cross-compile the daemon.
287 ----------------------------------------------------------------------
289 On my machines I can usually rebuild the appliance in around 3
290 minutes. If it takes much longer for you, use a local Fedora mirror
293 To use squid to cache yum downloads, read this first:
294 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
295 (In brief, because yum chooses random mirrors each time, squid doesn't
296 work very well with default yum configuration. To get around this,
297 choose a Fedora mirror which is close to you, set this with
298 './configure --with-mirror=[...]', and then proxy the whole lot
299 through squid by setting http_proxy environment variable).
301 You will also need to substantially increase the squid configuration
303 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
306 Porting to other Linux distros / non-Linux
307 ----------------------------------------------------------------------
309 libguestfs itself should be fairly portable to other Linux
310 distributions. Non-Linux ports are trickier, but we will accept
311 patches if they aren't too invasive.
313 The main porting issues are with the dependencies needed to build the
314 appliance. You will need to find or port the following packages
320 - rpm-python http://www.rpm.org/
321 - yum http://yum.baseurl.org/
322 - febootstrap http://people.redhat.com/~rjones/febootstrap/
325 Copyright and license information
326 ----------------------------------------------------------------------
328 Copyright (C) 2009-2010 Red Hat Inc.
330 The library is distributed under the LGPLv2+. The programs are
331 distributed under the GPLv2+. Please see the files COPYING and
332 COPYING.LIB for full license information.