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) to generate the manual pages and
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, but highly recommended) perl-libintl for translating perl code.
106 - (Optional) po4a for translating manpages and POD files.
108 - (Optional) PHP, phpize if you want to build the PHP bindings
110 Running ./configure will check you have all the requirements installed
115 ----------------------------------------------------------------------
117 Then make the daemon, library and root filesystem:
119 ./configure [--with-mirror=URI]
122 Use the optional --with-mirror parameter to specify the URI of a local
123 Fedora mirror. See the discussion of the MIRROR parameter in the
124 febootstrap(8) manpage.
126 Finally run the tests:
130 If everything works, you can install the library and tools by running
131 this command as root:
137 ----------------------------------------------------------------------
139 We provide packages for Fedora >= 11 in Fedora. Use those, or build
140 from our source RPMs - it's far simpler that way.
142 You can compile libguestfs on Fedora 10 but you cannot use it with the
143 version of qemu in Fedora 10. You need to compile your own qemu, see
144 section 'qemu' below.
147 RHEL / EPEL / CentOS etc
148 ----------------------------------------------------------------------
150 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
151 or build from our source RPMs.
155 ----------------------------------------------------------------------
157 libguestfs is now built as a package in Debian by Guido Gunther and
158 the other Debian libvirt maintainers. See:
160 http://wiki.debian.org/Teams/DebianLibvirtTeam#Packages
162 You can build for Debian in two different ways, either building a
163 Fedora-based appliance using febootstrap, yum, rpm, fakeroot,
164 fakechroot (all packaged in Debian). However the recommended way is
165 to build a Debian-based appliance using debootstrap and debirf.
167 Both ways are supported by the configure script.
171 ----------------------------------------------------------------------
173 By far the most common problem is with broken or incompatible
176 Different versions of qemu have problems booting the appliance for
177 different reasons. This varies between versions of qemu, and Linux
178 distributions which add their own patches.
180 If you find a problem, you could try using your own qemu built from
181 source (qemu is very easy to build from source), with a 'qemu
182 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
186 ----------------------------------------------------------------------
188 By default the configure script will look for qemu-kvm (KVM support).
189 You will need a reasonably recent processor for this to work. KVM is
190 much faster than using plain Qemu.
192 You may also need to enable KVM support for non-root users, by following
195 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
197 On some systems, this will work too:
201 On some systems, the chmod will not survive a reboot, and you will
202 need to make edits to the udev configuration.
206 ----------------------------------------------------------------------
208 Previous versions of libguestfs required something called "vmchannel".
209 Vmchannel is a special device given to virtual machines which allows
210 them to communicate in some way with the host, often (but not always)
211 without using a traditional network device. In reality, there is no
212 one thing called "vmchannel". This idea has been reimplemented
213 several times under the name vmchannel, and other hypervisors have
214 their own incompatible implementation(s) too.
216 In libguestfs <= 1.0.71, we required a specific vmchannel which is
217 properly known as "guestfwd" and has been upstream in qemu since here:
219 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
221 In libguestfs >= 1.0.71 we don't require any vmchannel implementation,
222 as long as qemu has been compiled with support for SLIRP (user mode
223 networking, or "-net user"), which is almost always the case.
225 In libguestfs >= 1.5.4 we switched again to using qemu's virtio-serial
226 and removed all the other vmchannels and the SLIRP channel.
230 ----------------------------------------------------------------------
232 If you configure with --enable-supermin then we will build a supermin
233 appliance (supermin = super-minimized). This is a very specialized
234 appliance which is built on-the-fly at runtime (specifically, when you
235 call guestfs_launch).
237 The normal appliance is a self-contained Linux operating system, based
238 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
239 copy of all the libraries and programs needed, like kernel, libc,
240 bash, coreutils etc etc.
242 The supermin appliance removes the kernel and all the executable
243 libraries and programs from the appliance. That just leaves a
244 skeleton of config files and some data files, which is obviously
245 massively smaller than the normal appliance. At runtime we rebuild
246 the appliance on-the-fly from the libraries and programs on the host
247 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
249 Although this process of rebuilding the appliance each time sounds
250 slow, it turns out to be faster than using the prebuilt appliance.
251 (Most of the saving comes from not compressing the appliance - it
252 transpires that decompressing the appliance is the slowest part of the
253 whole boot sequence). On my machine, a new appliance can be built in
254 under a fifth of a second, and the boot time is several seconds
257 The big advantage of the supermin appliance for distributions like
258 Fedora is that it gets security fixes automatically from the host, so
259 there is no need to rebuild the whole of libguestfs for a security
260 update in some underlying library.
262 There are several DISADVANTAGES:
264 It won't work at all except in very narrow, controlled cases like the
265 Fedora packaging case. We control the dependencies of the libguestfs
266 RPM tightly to ensure that the required binaries are actually present
269 Furthermore there are certain unlikely changes in the packages on the
270 host which could break a supermin appliance, eg. an updated library
271 which depends on an additional data file.
273 Also supermin appliances are subjected to changes in the host kernel
274 which might break compatibility with qemu -- these are, of course,
275 real bugs in any case.
277 Lastly, supermin appliances really can't be moved between branches of
278 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
279 they are not self-contained and they rely on certain libraries being
280 around. You shouldn't do this anyway.
282 Use supermin appliances with caution.
285 Notes on cross-architecture support
286 ----------------------------------------------------------------------
288 At the moment we basically don't support cross-architecture or
289 32-on-64. This limits what is possible for some guests. Filesystem
290 operations and FUSE will work fine, but running commands in guests may
293 To enable this requires work for cross-architecture and 32-on-64
294 support in febootstrap, fakeroot and fakechroot.
296 The daemon/ directory contains its own configure script. This is so
297 that in future we will be able to cross-compile the daemon.
301 ----------------------------------------------------------------------
303 On my machines I can usually rebuild the appliance in around 3
304 minutes. If it takes much longer for you, use a local Fedora mirror
307 To use squid to cache yum downloads, read this first:
308 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
309 (In brief, because yum chooses random mirrors each time, squid doesn't
310 work very well with default yum configuration. To get around this,
311 choose a Fedora mirror which is close to you, set this with
312 './configure --with-mirror=[...]', and then proxy the whole lot
313 through squid by setting http_proxy environment variable).
315 You will also need to substantially increase the squid configuration
317 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
320 Porting to other Linux distros / non-Linux
321 ----------------------------------------------------------------------
323 libguestfs itself should be fairly portable to other Linux
324 distributions. Non-Linux ports are trickier, but we will accept
325 patches if they aren't too invasive.
327 The main porting issues are with the dependencies needed to build the
328 appliance. You will need to find or port the following packages
334 - rpm-python http://www.rpm.org/
335 - yum http://yum.baseurl.org/
336 - febootstrap http://people.redhat.com/~rjones/febootstrap/
339 Copyright and license information
340 ----------------------------------------------------------------------
342 Copyright (C) 2009-2010 Red Hat Inc.
344 The library is distributed under the LGPLv2+. The programs are
345 distributed under the GPLv2+. Please see the files COPYING and
346 COPYING.LIB for full license information.