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
30 ----------------------------------------------------------------------
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) OCaml if you want to rebuild the generated files, and
64 also to build the OCaml bindings
66 - (Optional) local Fedora mirror
68 - (Optional) Perl if you want to build the perl bindings
70 - (Optional) Python if you want to build the python bindings
72 - (Optional) Ruby, rake if you want to build the ruby bindings
74 - (Optional) Java, JNI, jpackage-utils if you want to build the java
77 - (Optional) GHC if you want to build the Haskell bindings
79 - (Optional) Perl XML::XPath, Sys::Virt modules (for libvirt support
82 - (Optional, but highly recommended) perl-libintl for translating perl code.
84 Running ./configure will check you have all the requirements installed
89 ----------------------------------------------------------------------
91 Then make the daemon, library and root filesystem:
93 ./configure [--with-mirror=URI]
96 Use the optional --with-mirror parameter to specify the URI of a local
97 Fedora mirror. See the discussion of the MIRROR parameter in the
98 febootstrap(8) manpage.
100 Finally run the tests:
104 If everything works, you can install the library and tools by running
105 this command as root:
111 ----------------------------------------------------------------------
113 We provide packages for Fedora >= 11 in Fedora. Use those, or build
114 from our source RPMs - it's far simpler that way.
116 You can compile libguestfs on Fedora 10 but you cannot use it with the
117 version of qemu in Fedora 10. You need to compile your own qemu, see
118 section 'qemu' below.
121 RHEL / EPEL / CentOS etc
122 ----------------------------------------------------------------------
124 We provide packages in EPEL which cover RHEL/CentOS >= 5. Use those
125 or build from our source RPMs.
129 ----------------------------------------------------------------------
131 libguestfs is now built as a package in Debian by Guido Gunther and
132 the other Debian libvirt maintainers. See:
134 http://wiki.debian.org/Teams/DebianLibvirtTeam#Packages
136 You can build for Debian in two different ways, either building a
137 Fedora-based appliance using febootstrap, yum, rpm, fakeroot,
138 fakechroot (all packaged in Debian). However the recommended way is
139 to build a Debian-based appliance using debootstrap and debirf.
141 Both ways are supported by the configure script.
145 ----------------------------------------------------------------------
147 By far the most common problem is with broken or incompatible
150 Different versions of qemu have problems booting the appliance for
151 different reasons. This varies between versions of qemu, and Linux
152 distributions which add their own patches.
154 If you find a problem, you could try using your own qemu built from
155 source (qemu is very easy to build from source), with a 'qemu
156 wrapper'. Qemu wrappers are described in the guestfs(3) manpage.
160 ----------------------------------------------------------------------
162 By default the configure script will look for qemu-kvm (KVM support).
163 You will need a reasonably recent processor for this to work. KVM is
164 much faster than using plain Qemu.
166 You may also need to enable KVM support for non-root users, by following
169 http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F
171 On some systems, this will work too:
175 On some systems, the chmod will not survive a reboot, and you will
176 need to make edits to the udev configuration.
180 ----------------------------------------------------------------------
182 Previous versions of libguestfs required something called "vmchannel".
183 Vmchannel is a special device given to virtual machines which allows
184 them to communicate in some way with the host, often (but not always)
185 without using a traditional network device. In reality, there is no
186 one thing called "vmchannel". This idea has been reimplemented
187 several times under the name vmchannel, and other hypervisors have
188 their own incompatible implementation(s) too.
190 In libguestfs <= 1.0.71, we required a specific vmchannel which is
191 properly known as "guestfwd" and has been upstream in qemu since here:
193 http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html
195 In libguestfs >= 1.0.71 we don't require any vmchannel implementation,
196 as long as qemu has been compiled with support for SLIRP (user mode
197 networking, or "-net user"), which is almost always the case.
199 However we still offer the ability to use vmchannel, and in future we
200 may add support for other types of qemu, which is useful in a few
201 cases, specifically where qemu packagers decide to compile out support
202 for SLIRP (qemu packagers: please don't do this).
206 ----------------------------------------------------------------------
208 If you configure with --enable-supermin then we will build a supermin
209 appliance (supermin = super-minimized). This is a very specialized
210 appliance which is built on-the-fly at runtime (specifically, when you
211 call guestfs_launch).
213 The normal appliance is a self-contained Linux operating system, based
214 on the Fedora/RHEL/CentOS Linux distro. So it contains a complete
215 copy of all the libraries and programs needed, like kernel, libc,
216 bash, coreutils etc etc.
218 The supermin appliance removes the kernel and all the executable
219 libraries and programs from the appliance. That just leaves a
220 skeleton of config files and some data files, which is obviously
221 massively smaller than the normal appliance. At runtime we rebuild
222 the appliance on-the-fly from the libraries and programs on the host
223 (eg. pulling in the real /lib/libc.so, the real /bin/bash etc.)
225 Although this process of rebuilding the appliance each time sounds
226 slow, it turns out to be faster than using the prebuilt appliance.
227 (Most of the saving comes from not compressing the appliance - it
228 transpires that decompressing the appliance is the slowest part of the
229 whole boot sequence). On my machine, a new appliance can be built in
230 under a fifth of a second, and the boot time is several seconds
233 The big advantage of the supermin appliance for distributions like
234 Fedora is that it gets security fixes automatically from the host, so
235 there is no need to rebuild the whole of libguestfs for a security
236 update in some underlying library.
238 There are several DISADVANTAGES:
240 It won't work at all except in very narrow, controlled cases like the
241 Fedora packaging case. We control the dependencies of the libguestfs
242 RPM tightly to ensure that the required binaries are actually present
245 Furthermore there are certain unlikely changes in the packages on the
246 host which could break a supermin appliance, eg. an updated library
247 which depends on an additional data file.
249 Also supermin appliances are subjected to changes in the host kernel
250 which might break compatibility with qemu -- these are, of course,
251 real bugs in any case.
253 Lastly, supermin appliances really can't be moved between branches of
254 distributions (eg. built on Fedora 12 and moved to Fedora 10) because
255 they are not self-contained and they rely on certain libraries being
256 around. You shouldn't do this anyway.
258 Use supermin appliances with caution.
261 Notes on cross-architecture support
262 ----------------------------------------------------------------------
264 At the moment we basically don't support cross-architecture or
265 32-on-64. This limits what is possible for some guests. Filesystem
266 operations and FTP export will work fine, but running commands in
267 guests may not be possible.
269 To enable this requires work for cross-architecture and 32-on-64
270 support in febootstrap, fakeroot and fakechroot.
272 The daemon/ directory contains its own configure script. This is so
273 that in future we will be able to cross-compile the daemon.
277 ----------------------------------------------------------------------
279 On my machines I can usually rebuild the appliance in around 3
280 minutes. If it takes much longer for you, use a local Fedora mirror
283 To use squid to cache yum downloads, read this first:
284 https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
285 (In brief, because yum chooses random mirrors each time, squid doesn't
286 work very well with default yum configuration. To get around this,
287 choose a Fedora mirror which is close to you, set this with
288 './configure --with-mirror=[...]', and then proxy the whole lot
289 through squid by setting http_proxy environment variable).
291 You will also need to substantially increase the squid configuration
293 http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads
296 Porting to other Linux distros / non-Linux
297 ----------------------------------------------------------------------
299 libguestfs itself should be fairly portable to other Linux
300 distributions. Non-Linux ports are trickier, but we will accept
301 patches if they aren't too invasive.
303 The main porting issues are with the dependencies needed to build the
304 appliance. You will need to find or port the following packages
310 - rpm-python http://www.rpm.org/
311 - yum http://yum.baseurl.org/
312 - febootstrap http://et.redhat.com/~rjones/febootstrap/
315 Copyright and license information
316 ----------------------------------------------------------------------
318 Copyright (C) 2009 Red Hat Inc.
320 The library is distributed under the LGPLv2+. The programs are
321 distributed under the GPLv2+. Please see the files COPYING and
322 COPYING.LIB for full license information.