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 FTP.
18 Libguestfs is a library that can be linked with C and C++ management
19 programs (or management programs written in OCaml, Perl, Python, Ruby, Java
20 or Haskell). You can also use it from shell scripts or the command line.
22 Libguestfs was written by Richard W.M. Jones (rjones@redhat.com) and
23 hacked on by lots of other people. For discussion, development,
24 patches, etc. please use the mailing list:
26 http://www.redhat.com/mailman/listinfo/libguestfs
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32 http://libguestfs.org/
36 ----------------------------------------------------------------------
38 - recent QEMU >= 0.10 with vmchannel support
39 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
47 - XDR, rpcgen (on Linux these are provided by glibc)
49 - squashfs-tools (mksquashfs only)
51 - (Optional) Augeas (http://augeas.net/)
53 - perldoc (pod2man, pod2text) to generate the manual pages and
56 - (Optional) Readline to have nicer command-line editing in guestfish.
58 - (Optional) 'reged' program from chntpw to decode Windows registry
59 entries (http://home.eunet.no/~pnordahl/ntpasswd/)
61 - (Optional) OCaml if you want to rebuild the generated files, and
62 also to build the OCaml bindings
64 - (Optional) local Fedora mirror
66 - (Optional) Perl if you want to build the perl bindings
68 - (Optional) Python if you want to build the python bindings
70 - (Optional) Ruby, rake if you want to build the ruby bindings
72 - (Optional) Java, JNI, jpackage-utils if you want to build the java
75 - (Optional) GHC if you want to build the Haskell bindings
77 - (Optional) Perl XML::XPath, Sys::Virt modules (for libvirt support
80 Running ./configure will check you have all the requirements installed
85 ----------------------------------------------------------------------
87 Then make the daemon, library and root filesystem:
89 ./configure [--with-mirror=URI]
92 Use the optional --with-mirror parameter to specify the URI of a local
93 Fedora mirror. See the discussion of the MIRROR parameter in the
94 febootstrap(8) manpage.
96 Finally run the tests:
100 If everything works, you can install the library and tools by running
101 this command as root:
107 ----------------------------------------------------------------------
109 We provide packages for Fedora >= 11 in Fedora. Use those, or build
110 from our source RPMs - it's far simpler that way.
112 You can compile libguestfs on Fedora 10 but you cannot use it with the
113 version of qemu in Fedora 10. You need to compile your own qemu, see
114 section 'qemu' below.
117 RHEL / EPEL / CentOS etc
118 ----------------------------------------------------------------------
120 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
121 or build from our source RPMs.
125 ----------------------------------------------------------------------
127 libguestfs is now built as a package in Debian by Guido Gunther and
128 the other Debian libvirt maintainers. See:
130 http://wiki.debian.org/Teams/DebianLibvirtTeam#Packages
132 You can build for Debian in two different ways, either building a
133 Fedora-based appliance using febootstrap, yum, rpm, fakeroot,
134 fakechroot (all packaged in Debian). However the recommended way is
135 to build a Debian-based appliance using debootstrap and debirf.
137 Both ways are supported by the configure script.
141 ----------------------------------------------------------------------
143 By far the most common problem is with broken or incompatible
146 First of all, you need qemu >= 0.10.4, which contains a vmchannel
147 implementation. There are several, conflicting, incompatible things
148 called 'vmchannel' which at one time or another have been added or
149 proposed for qemu/KVM. The _only_ one we support is this one:
151 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
153 Secondly, different versions of qemu have problems booting the
154 appliance for different reasons. This varies between versions of
155 qemu, and Linux distributions which add their own patches.
157 If you find a problem, you could try using your own qemu built from
158 source (qemu is very easy to build from source), with a 'qemu
159 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
163 ----------------------------------------------------------------------
165 By default the configure script will look for qemu-kvm (KVM support).
166 You will need a reasonably recent processor for this to work. KVM is
167 much faster than using plain Qemu.
169 You may also need to enable KVM support for non-root users, by following
172 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
174 On some systems, this will work too:
178 On some systems, the chmod will not survive a reboot, and you will
179 need to make edits to the udev configuration.
183 ----------------------------------------------------------------------
185 If you configure with --enable-supermin then we will build a supermin
186 appliance (supermin = super-minimized). This is a very specialized
187 appliance which is built on-the-fly at runtime (specifically, when you
188 call guestfs_launch).
190 The normal appliance is a self-contained Linux operating system, based
191 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
192 copy of all the libraries and programs needed, like kernel, libc,
193 bash, coreutils etc etc.
195 The supermin appliance removes the kernel and all the executable
196 libraries and programs from the appliance. That just leaves a
197 skeleton of config files and some data files, which is obviously
198 massively smaller than the normal appliance. At runtime we rebuild
199 the appliance on-the-fly from the libraries and programs on the host
200 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
202 Although this process of rebuilding the appliance each time sounds
203 slow, it turns out to be faster than using the prebuilt appliance.
204 (Most of the saving comes from not compressing the appliance - it
205 transpires that decompressing the appliance is the slowest part of the
206 whole boot sequence). On my machine, a new appliance can be built in
207 under a fifth of a second, and the boot time is several seconds
210 The big advantage of the supermin appliance for distributions like
211 Fedora is that it gets security fixes automatically from the host, so
212 there is no need to rebuild the whole of libguestfs for a security
213 update in some underlying library.
215 There are several DISADVANTAGES:
217 It won't work at all except in very narrow, controlled cases like the
218 Fedora packaging case. We control the dependencies of the libguestfs
219 RPM tightly to ensure that the required binaries are actually present
222 Furthermore there are certain unlikely changes in the packages on the
223 host which could break a supermin appliance, eg. an updated library
224 which depends on an additional data file.
226 Also supermin appliances are subjected to changes in the host kernel
227 which might break compatibility with qemu -- these are, of course,
228 real bugs in any case.
230 Lastly, supermin appliances really can't be moved between branches of
231 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
232 they are not self-contained and they rely on certain libraries being
233 around. You shouldn't do this anyway.
235 Use supermin appliances with caution.
238 Notes on cross-architecture support
239 ----------------------------------------------------------------------
241 At the moment we basically don't support cross-architecture or
242 32-on-64. This limits what is possible for some guests. Filesystem
243 operations and FTP export will work fine, but running commands in
244 guests may not be possible.
246 To enable this requires work for cross-architecture and 32-on-64
247 support in febootstrap, fakeroot and fakechroot.
249 The daemon/ directory contains its own configure script. This is so
250 that in future we will be able to cross-compile the daemon.
254 ----------------------------------------------------------------------
256 On my machines I can usually rebuild the appliance in around 3
257 minutes. If it takes much longer for you, use a local Fedora mirror
260 To use squid to cache yum downloads, read this first:
261 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
262 (In brief, because yum chooses random mirrors each time, squid doesn't
263 work very well with default yum configuration. To get around this,
264 choose a Fedora mirror which is close to you, set this with
265 './configure --with-mirror=[...]', and then proxy the whole lot
266 through squid by setting http_proxy environment variable).
268 You will also need to substantially increase the squid configuration
270 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
273 Porting to other Linux distros / non-Linux
274 ----------------------------------------------------------------------
276 libguestfs itself should be fairly portable to other Linux
277 distributions. Non-Linux ports are trickier, but we will accept
278 patches if they aren't too invasive.
280 The main porting issues are with the dependencies needed to build the
281 appliance. You will need to find or port the following packages
287 - rpm-python http://www.rpm.org/
288 - yum http://yum.baseurl.org/
289 - febootstrap http://et.redhat.com/~rjones/febootstrap/
292 Copyright and license information
293 ----------------------------------------------------------------------
295 Copyright (C) 2009 Red Hat Inc.
297 The library is distributed under the LGPLv2+. The programs are
298 distributed under the GPLv2+. Please see the files COPYING and
299 COPYING.LIB for full license information.