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 - genisoimage / mkisofs
53 - (Optional) Augeas (http://augeas.net/)
55 - perldoc (pod2man, pod2text) to generate the manual pages and
58 - (Optional) Readline to have nicer command-line editing in guestfish.
60 - (Optional) 'reged' program from chntpw to decode Windows registry
61 entries (http://home.eunet.no/~pnordahl/ntpasswd/)
63 - (Optional) xmllint to validate virt-inspector RELAX NG schema
65 - (Optional) OCaml if you want to rebuild the generated files, and
66 also to build the OCaml bindings
68 - (Optional) local Fedora mirror
70 - (Optional) Perl if you want to build the perl bindings
72 - (Optional) Python if you want to build the python bindings
74 - (Optional) Ruby, rake if you want to build the ruby bindings
76 - (Optional) Java, JNI, jpackage-utils if you want to build the java
79 - (Optional) GHC if you want to build the Haskell bindings
81 - (Optional) Perl XML::XPath, Sys::Virt modules (for libvirt support
84 - (Optional, but highly recommended) perl-libintl for translating perl code.
86 Running ./configure will check you have all the requirements installed
91 ----------------------------------------------------------------------
93 Then make the daemon, library and root filesystem:
95 ./configure [--with-mirror=URI]
98 Use the optional --with-mirror parameter to specify the URI of a local
99 Fedora mirror. See the discussion of the MIRROR parameter in the
100 febootstrap(8) manpage.
102 Finally run the tests:
106 If everything works, you can install the library and tools by running
107 this command as root:
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115 We provide packages for Fedora >= 11 in Fedora. Use those, or build
116 from our source RPMs - it's far simpler that way.
118 You can compile libguestfs on Fedora 10 but you cannot use it with the
119 version of qemu in Fedora 10. You need to compile your own qemu, see
120 section 'qemu' below.
123 RHEL / EPEL / CentOS etc
124 ----------------------------------------------------------------------
126 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
127 or build from our source RPMs.
131 ----------------------------------------------------------------------
133 libguestfs is now built as a package in Debian by Guido Gunther and
134 the other Debian libvirt maintainers. See:
136 http://wiki.debian.org/Teams/DebianLibvirtTeam#Packages
138 You can build for Debian in two different ways, either building a
139 Fedora-based appliance using febootstrap, yum, rpm, fakeroot,
140 fakechroot (all packaged in Debian). However the recommended way is
141 to build a Debian-based appliance using debootstrap and debirf.
143 Both ways are supported by the configure script.
147 ----------------------------------------------------------------------
149 By far the most common problem is with broken or incompatible
152 Different versions of qemu have problems booting the appliance for
153 different reasons. This varies between versions of qemu, and Linux
154 distributions which add their own patches.
156 If you find a problem, you could try using your own qemu built from
157 source (qemu is very easy to build from source), with a 'qemu
158 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
162 ----------------------------------------------------------------------
164 By default the configure script will look for qemu-kvm (KVM support).
165 You will need a reasonably recent processor for this to work. KVM is
166 much faster than using plain Qemu.
168 You may also need to enable KVM support for non-root users, by following
171 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
173 On some systems, this will work too:
177 On some systems, the chmod will not survive a reboot, and you will
178 need to make edits to the udev configuration.
182 ----------------------------------------------------------------------
184 Previous versions of libguestfs required something called "vmchannel".
185 Vmchannel is a special device given to virtual machines which allows
186 them to communicate in some way with the host, often (but not always)
187 without using a traditional network device. In reality, there is no
188 one thing called "vmchannel". This idea has been reimplemented
189 several times under the name vmchannel, and other hypervisors have
190 their own incompatible implementation(s) too.
192 In libguestfs <= 1.0.71, we required a specific vmchannel which is
193 properly known as "guestfwd" and has been upstream in qemu since here:
195 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
197 In libguestfs >= 1.0.71 we don't require any vmchannel implementation,
198 as long as qemu has been compiled with support for SLIRP (user mode
199 networking, or "-net user"), which is almost always the case.
201 However we still offer the ability to use vmchannel, and in future we
202 may add support for other types of qemu, which is useful in a few
203 cases, specifically where qemu packagers decide to compile out support
204 for SLIRP (qemu packagers: please don't do this).
208 ----------------------------------------------------------------------
210 If you configure with --enable-supermin then we will build a supermin
211 appliance (supermin = super-minimized). This is a very specialized
212 appliance which is built on-the-fly at runtime (specifically, when you
213 call guestfs_launch).
215 The normal appliance is a self-contained Linux operating system, based
216 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
217 copy of all the libraries and programs needed, like kernel, libc,
218 bash, coreutils etc etc.
220 The supermin appliance removes the kernel and all the executable
221 libraries and programs from the appliance. That just leaves a
222 skeleton of config files and some data files, which is obviously
223 massively smaller than the normal appliance. At runtime we rebuild
224 the appliance on-the-fly from the libraries and programs on the host
225 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
227 Although this process of rebuilding the appliance each time sounds
228 slow, it turns out to be faster than using the prebuilt appliance.
229 (Most of the saving comes from not compressing the appliance - it
230 transpires that decompressing the appliance is the slowest part of the
231 whole boot sequence). On my machine, a new appliance can be built in
232 under a fifth of a second, and the boot time is several seconds
235 The big advantage of the supermin appliance for distributions like
236 Fedora is that it gets security fixes automatically from the host, so
237 there is no need to rebuild the whole of libguestfs for a security
238 update in some underlying library.
240 There are several DISADVANTAGES:
242 It won't work at all except in very narrow, controlled cases like the
243 Fedora packaging case. We control the dependencies of the libguestfs
244 RPM tightly to ensure that the required binaries are actually present
247 Furthermore there are certain unlikely changes in the packages on the
248 host which could break a supermin appliance, eg. an updated library
249 which depends on an additional data file.
251 Also supermin appliances are subjected to changes in the host kernel
252 which might break compatibility with qemu -- these are, of course,
253 real bugs in any case.
255 Lastly, supermin appliances really can't be moved between branches of
256 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
257 they are not self-contained and they rely on certain libraries being
258 around. You shouldn't do this anyway.
260 Use supermin appliances with caution.
263 Notes on cross-architecture support
264 ----------------------------------------------------------------------
266 At the moment we basically don't support cross-architecture or
267 32-on-64. This limits what is possible for some guests. Filesystem
268 operations and FTP export will work fine, but running commands in
269 guests may not be possible.
271 To enable this requires work for cross-architecture and 32-on-64
272 support in febootstrap, fakeroot and fakechroot.
274 The daemon/ directory contains its own configure script. This is so
275 that in future we will be able to cross-compile the daemon.
279 ----------------------------------------------------------------------
281 On my machines I can usually rebuild the appliance in around 3
282 minutes. If it takes much longer for you, use a local Fedora mirror
285 To use squid to cache yum downloads, read this first:
286 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
287 (In brief, because yum chooses random mirrors each time, squid doesn't
288 work very well with default yum configuration. To get around this,
289 choose a Fedora mirror which is close to you, set this with
290 './configure --with-mirror=[...]', and then proxy the whole lot
291 through squid by setting http_proxy environment variable).
293 You will also need to substantially increase the squid configuration
295 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
298 Porting to other Linux distros / non-Linux
299 ----------------------------------------------------------------------
301 libguestfs itself should be fairly portable to other Linux
302 distributions. Non-Linux ports are trickier, but we will accept
303 patches if they aren't too invasive.
305 The main porting issues are with the dependencies needed to build the
306 appliance. You will need to find or port the following packages
312 - rpm-python http://www.rpm.org/
313 - yum http://yum.baseurl.org/
314 - febootstrap http://et.redhat.com/~rjones/febootstrap/
317 Copyright and license information
318 ----------------------------------------------------------------------
320 Copyright (C) 2009 Red Hat Inc.
322 The library is distributed under the LGPLv2+. The programs are
323 distributed under the GPLv2+. Please see the files COPYING and
324 COPYING.LIB for full license information.