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).
23 For discussion please use the fedora-virt mailing list:
25 https://www.redhat.com/mailman/listinfo/fedora-virt
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31 http://libguestfs.org/
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37 - recent QEMU >= 0.10 with vmchannel support
38 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
46 - XDR, rpcgen (on Linux these are provided by glibc)
48 - squashfs-tools (mksquashfs only)
50 - (Optional) Augeas (http://augeas.net/)
52 - perldoc (pod2man, pod2text) to generate the manual pages and
55 - (Optional) Readline to have nicer command-line editing in guestfish.
57 - (Optional) 'reged' program from chntpw to decode Windows registry
58 entries (http://home.eunet.no/~pnordahl/ntpasswd/)
60 - (Optional) OCaml if you want to rebuild the generated files, and
61 also to build the OCaml bindings
63 - (Optional) local Fedora mirror
65 - (Optional) Perl if you want to build the perl bindings
67 - (Optional) Python if you want to build the python bindings
69 - (Optional) Ruby, rake if you want to build the ruby bindings
71 - (Optional) Java, JNI, jpackage-utils if you want to build the java
74 - (Optional) GHC if you want to build the Haskell bindings
76 Running ./configure will check you have all the requirements installed
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83 Then make the daemon, library and root filesystem:
85 ./configure [--with-mirror=URI]
88 Use the optional --with-mirror parameter to specify the URI of a local
89 Fedora mirror. See the discussion of the MIRROR parameter in the
90 febootstrap(8) manpage.
92 Finally run the tests:
96 If everything works, you can install the library and tools by running
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105 We provide packages for Fedora >= 11 in Fedora. Use those, or build
106 from our source RPMs - it's far simpler that way.
108 You can compile libguestfs on Fedora 10 but you cannot use it with the
109 version of qemu in Fedora 10. You need to compile your own qemu, see
110 section 'qemu' below.
113 RHEL / EPEL / CentOS etc
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116 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
117 or build from our source RPMs.
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123 libguestfs should build and run on Debian.
125 febootstrap, yum, rpm, fakeroot, fakechroot are all packaged in
128 Please see the fedora-virt mailing list for the status of libguestfs
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135 By far the most common problem is with broken or incompatible
138 First of all, you need qemu >= 0.10.4, which contains a vmchannel
139 implementation. There are several, conflicting, incompatible things
140 called 'vmchannel' which at one time or another have been added or
141 proposed for qemu/KVM. The _only_ one we support is this one:
143 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
145 Secondly, different versions of qemu have problems booting the
146 appliance for different reasons. This varies between versions of
147 qemu, and Linux distributions which add their own patches.
149 If you find a problem, you could try using your own qemu built from
150 source (qemu is very easy to build from source), with a 'qemu
151 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
155 ----------------------------------------------------------------------
157 By default the configure script will look for qemu-kvm (KVM support).
158 You will need a reasonably recent processor for this to work. KVM is
159 much faster than using plain Qemu.
161 You may also need to enable KVM support for non-root users, by following
164 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
166 On some systems, this will work too:
170 On some systems, the chmod will not survive a reboot, and you will
171 need to make edits to the udev configuration.
175 ----------------------------------------------------------------------
177 If you configure with --enable-supermin then we will build a supermin
178 appliance (supermin = super-minimized). This is a very specialized
179 appliance which is built on-the-fly at runtime (specifically, when you
180 call guestfs_launch).
182 The normal appliance is a self-contained Linux operating system, based
183 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
184 copy of all the libraries and programs needed, like kernel, libc,
185 bash, coreutils etc etc.
187 The supermin appliance removes the kernel and all the executable
188 libraries and programs from the appliance. That just leaves a
189 skeleton of config files and some data files, which is obviously
190 massively smaller than the normal appliance. At runtime we rebuild
191 the appliance on-the-fly from the libraries and programs on the host
192 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
194 Although this process of rebuilding the appliance each time sounds
195 slow, it turns out to be faster than using the prebuilt appliance.
196 (Most of the saving comes from not compressing the appliance - it
197 transpires that decompressing the appliance is the slowest part of the
198 whole boot sequence). On my machine, a new appliance can be built in
199 under a fifth of a second, and the boot time is several seconds
202 The big advantage of the supermin appliance for distributions like
203 Fedora is that it gets security fixes automatically from the host, so
204 there is no need to rebuild the whole of libguestfs for a security
205 update in some underlying library.
207 There are several DISADVANTAGES:
209 It won't work at all except in very narrow, controlled cases like the
210 Fedora packaging case. We control the dependencies of the libguestfs
211 RPM tightly to ensure that the required binaries are actually present
214 Furthermore there are certain unlikely changes in the packages on the
215 host which could break a supermin appliance, eg. an updated library
216 which depends on an additional data file.
218 Also supermin appliances are subjected to changes in the host kernel
219 which might break compatibility with qemu -- these are, of course,
220 real bugs in any case.
222 Lastly, supermin appliances really can't be moved between branches of
223 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
224 they are not self-contained and they rely on certain libraries being
225 around. You shouldn't do this anyway.
227 Use supermin appliances with caution.
230 Notes on cross-architecture support
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233 At the moment we basically don't support cross-architecture or
234 32-on-64. This limits what is possible for some guests. Filesystem
235 operations and FTP export will work fine, but running commands in
236 guests may not be possible.
238 To enable this requires work for cross-architecture and 32-on-64
239 support in febootstrap, fakeroot and fakechroot.
241 The daemon/ directory contains its own configure script. This is so
242 that in future we will be able to cross-compile the daemon.
246 ----------------------------------------------------------------------
248 On my machines I can usually rebuild the appliance in around 3
249 minutes. If it takes much longer for you, use a local Fedora mirror
252 To use squid to cache yum downloads, read this first:
253 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
254 (In brief, because yum chooses random mirrors each time, squid doesn't
255 work very well with default yum configuration. To get around this,
256 choose a Fedora mirror which is close to you, set this with
257 './configure --with-mirror=[...]', and then proxy the whole lot
258 through squid by setting http_proxy environment variable).
260 You will also need to substantially increase the squid configuration
262 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
265 Porting to other Linux distros / non-Linux
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268 libguestfs itself should be fairly portable to other Linux
269 distributions. Non-Linux ports are trickier, but we will accept
270 patches if they aren't too invasive.
272 The main porting issues are with the dependencies needed to build the
273 appliance. You will need to find or port the following packages
279 - rpm-python http://www.rpm.org/
280 - yum http://yum.baseurl.org/
281 - febootstrap http://et.redhat.com/~rjones/febootstrap/
284 Copyright and license information
285 ----------------------------------------------------------------------
287 Copyright (C) 2009 Red Hat Inc.
289 The library is distributed under the LGPLv2+. The programs are
290 distributed under the GPLv2+. Please see the files COPYING and
291 COPYING.LIB for full license information.