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/
35 ----------------------------------------------------------------------
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 - (Optional) Perl XML::XPath, Sys::Virt modules (for libvirt support
79 Running ./configure will check you have all the requirements installed
84 ----------------------------------------------------------------------
86 Then make the daemon, library and root filesystem:
88 ./configure [--with-mirror=URI]
91 Use the optional --with-mirror parameter to specify the URI of a local
92 Fedora mirror. See the discussion of the MIRROR parameter in the
93 febootstrap(8) manpage.
95 Finally run the tests:
99 If everything works, you can install the library and tools by running
100 this command as root:
106 ----------------------------------------------------------------------
108 We provide packages for Fedora >= 11 in Fedora. Use those, or build
109 from our source RPMs - it's far simpler that way.
111 You can compile libguestfs on Fedora 10 but you cannot use it with the
112 version of qemu in Fedora 10. You need to compile your own qemu, see
113 section 'qemu' below.
116 RHEL / EPEL / CentOS etc
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119 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
120 or build from our source RPMs.
124 ----------------------------------------------------------------------
126 libguestfs should build and run on Debian.
128 febootstrap, yum, rpm, fakeroot, fakechroot are all packaged in
131 Please see the fedora-virt mailing list for the status of libguestfs
136 ----------------------------------------------------------------------
138 By far the most common problem is with broken or incompatible
141 First of all, you need qemu >= 0.10.4, which contains a vmchannel
142 implementation. There are several, conflicting, incompatible things
143 called 'vmchannel' which at one time or another have been added or
144 proposed for qemu/KVM. The _only_ one we support is this one:
146 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
148 Secondly, different versions of qemu have problems booting the
149 appliance for different reasons. This varies between versions of
150 qemu, and Linux distributions which add their own patches.
152 If you find a problem, you could try using your own qemu built from
153 source (qemu is very easy to build from source), with a 'qemu
154 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
158 ----------------------------------------------------------------------
160 By default the configure script will look for qemu-kvm (KVM support).
161 You will need a reasonably recent processor for this to work. KVM is
162 much faster than using plain Qemu.
164 You may also need to enable KVM support for non-root users, by following
167 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
169 On some systems, this will work too:
173 On some systems, the chmod will not survive a reboot, and you will
174 need to make edits to the udev configuration.
178 ----------------------------------------------------------------------
180 If you configure with --enable-supermin then we will build a supermin
181 appliance (supermin = super-minimized). This is a very specialized
182 appliance which is built on-the-fly at runtime (specifically, when you
183 call guestfs_launch).
185 The normal appliance is a self-contained Linux operating system, based
186 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
187 copy of all the libraries and programs needed, like kernel, libc,
188 bash, coreutils etc etc.
190 The supermin appliance removes the kernel and all the executable
191 libraries and programs from the appliance. That just leaves a
192 skeleton of config files and some data files, which is obviously
193 massively smaller than the normal appliance. At runtime we rebuild
194 the appliance on-the-fly from the libraries and programs on the host
195 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
197 Although this process of rebuilding the appliance each time sounds
198 slow, it turns out to be faster than using the prebuilt appliance.
199 (Most of the saving comes from not compressing the appliance - it
200 transpires that decompressing the appliance is the slowest part of the
201 whole boot sequence). On my machine, a new appliance can be built in
202 under a fifth of a second, and the boot time is several seconds
205 The big advantage of the supermin appliance for distributions like
206 Fedora is that it gets security fixes automatically from the host, so
207 there is no need to rebuild the whole of libguestfs for a security
208 update in some underlying library.
210 There are several DISADVANTAGES:
212 It won't work at all except in very narrow, controlled cases like the
213 Fedora packaging case. We control the dependencies of the libguestfs
214 RPM tightly to ensure that the required binaries are actually present
217 Furthermore there are certain unlikely changes in the packages on the
218 host which could break a supermin appliance, eg. an updated library
219 which depends on an additional data file.
221 Also supermin appliances are subjected to changes in the host kernel
222 which might break compatibility with qemu -- these are, of course,
223 real bugs in any case.
225 Lastly, supermin appliances really can't be moved between branches of
226 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
227 they are not self-contained and they rely on certain libraries being
228 around. You shouldn't do this anyway.
230 Use supermin appliances with caution.
233 Notes on cross-architecture support
234 ----------------------------------------------------------------------
236 At the moment we basically don't support cross-architecture or
237 32-on-64. This limits what is possible for some guests. Filesystem
238 operations and FTP export will work fine, but running commands in
239 guests may not be possible.
241 To enable this requires work for cross-architecture and 32-on-64
242 support in febootstrap, fakeroot and fakechroot.
244 The daemon/ directory contains its own configure script. This is so
245 that in future we will be able to cross-compile the daemon.
249 ----------------------------------------------------------------------
251 On my machines I can usually rebuild the appliance in around 3
252 minutes. If it takes much longer for you, use a local Fedora mirror
255 To use squid to cache yum downloads, read this first:
256 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
257 (In brief, because yum chooses random mirrors each time, squid doesn't
258 work very well with default yum configuration. To get around this,
259 choose a Fedora mirror which is close to you, set this with
260 './configure --with-mirror=[...]', and then proxy the whole lot
261 through squid by setting http_proxy environment variable).
263 You will also need to substantially increase the squid configuration
265 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
268 Porting to other Linux distros / non-Linux
269 ----------------------------------------------------------------------
271 libguestfs itself should be fairly portable to other Linux
272 distributions. Non-Linux ports are trickier, but we will accept
273 patches if they aren't too invasive.
275 The main porting issues are with the dependencies needed to build the
276 appliance. You will need to find or port the following packages
282 - rpm-python http://www.rpm.org/
283 - yum http://yum.baseurl.org/
284 - febootstrap http://et.redhat.com/~rjones/febootstrap/
287 Copyright and license information
288 ----------------------------------------------------------------------
290 Copyright (C) 2009 Red Hat Inc.
292 The library is distributed under the LGPLv2+. The programs are
293 distributed under the GPLv2+. Please see the files COPYING and
294 COPYING.LIB for full license information.