path: root/README

Libguestfs is a library for accessing and modifying guest disk images.
Amongst the things this is good for: making batch configuration
changes to guests, getting disk used/free statistics (see also:
virt-df), migrating between virtualization systems (see also:
virt-p2v), performing partial backups, performing partial guest
clones, cloning guests and changing registry/UUID/hostname info, and
much else besides.

Libguestfs uses Linux kernel and qemu code, and can access any type of
guest filesystem that Linux and qemu can, including but not limited
to: ext2/3/4, btrfs, FAT and NTFS, LVM, many different disk partition
schemes, qcow, qcow2, vmdk.

Libguestfs provides ways to enumerate guest storage (eg. partitions,
LVs, what filesystem is in each LV, etc.).  It can also run commands
in the context of the guest.  Also you can access filesystems over
FUSE.

Libguestfs is a library that can be linked with C and C++ management
programs (or management programs written in OCaml, Perl, Python, Ruby,
Java, PHP, Haskell or C#).  You can also use it from shell scripts or the
command line.

Libguestfs was written by Richard W.M. Jones (rjones@redhat.com) and
hacked on by lots of other people.  For discussion, development,
patches, etc. please use the mailing list:

  http://www.redhat.com/mailman/listinfo/libguestfs


Home page
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  http://libguestfs.org/


Requirements
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- recent QEMU >= 0.12 with virtio-serial support

- febootstrap >= 3.0
     *NB*: febootstrap 2.x WILL NOT WORK
           febootstrap 3.x is distro-independent, and is required on
             Debian and other distros too

- XDR, rpcgen (on Linux these are provided by glibc)

- pcre (Perl Compatible Regular Expressions C library) (optional)

- libmagic (the library that corresponds to the 'file' command) (optional)

- libvirt (optional)

- libxml2 (optional)

- Augeas (http://augeas.net/) (optional)

- gperf

- squashfs-tools (mksquashfs only)

- genisoimage / mkisofs

- hivex >= 1.2.1 (http://libguestfs.org/download)

- (Optional) Berkeley DB 'db_dump' and 'db_load' utilities
  (db4-utils or db4.X-util or similar)

- (Optional) FUSE to build the FUSE module

- perldoc (pod2man, pod2text, pod2html) to generate the manual pages
  and other documentation.

- (Optional) Readline to have nicer command-line editing in guestfish.

- (Optional) xmllint to validate virt-inspector RELAX NG schema

- (Optional) OCaml if you want to rebuild the generated files, and
  also to build the OCaml bindings

- (Optional) local Fedora mirror

- (Optional) Perl if you want to build the perl bindings

- (Optional) Python if you want to build the python bindings

- (Optional) Ruby, rake if you want to build the ruby bindings

- (Optional) Java, JNI, jpackage-utils if you want to build the java
bindings

- (Optional) GHC if you want to build the Haskell bindings

- (Optional) Perl Sys::Virt module.

- (Optional) Perl Win::Hivex module.

- (Optional) Perl Pod::Usage module.

- (Optional) Perl Test::More module (from perl Test::Simple).

- (Optional) Perl String::ShellQuote module.

- (Optional, but highly recommended) perl-libintl for translating perl code.

- (Optional) po4a for translating manpages and POD files.

- (Optional) PHP, phpize if you want to build the PHP bindings

Running ./configure will check you have all the requirements installed
on your machine.


Building
----------------------------------------------------------------------

Then make the daemon, library and root filesystem:

  ./configure [--with-mirror=URI]
  make

Use the optional --with-mirror parameter to specify the URI of a local
Fedora mirror.  See the discussion of the MIRROR parameter in the
febootstrap(8) manpage.

Finally run the tests:

  make check

If everything works, you can install the library and tools by running
this command as root:

  make install


qemu
----------------------------------------------------------------------

By far the most common problem is with broken or incompatible
qemu releases.

Different versions of qemu have problems booting the appliance for
different reasons.  This varies between versions of qemu, and Linux
distributions which add their own patches.

If you find a problem, you could try using your own qemu built from
source (qemu is very easy to build from source), with a 'qemu
wrapper'.  Qemu wrappers are described in the guestfs(3) manpage.


Note on using KVM
----------------------------------------------------------------------

By default the configure script will look for qemu-kvm (KVM support).
You will need a reasonably recent processor for this to work.  KVM is
much faster than using plain Qemu.

You may also need to enable KVM support for non-root users, by following
these instructions:

  http://www.linux-kvm.org/page/FAQ#How_can_I_use_kvm_with_a_non-privileged_user.3F

On some systems, this will work too:

  chmod o+rw /dev/kvm

On some systems, the chmod will not survive a reboot, and you will
need to make edits to the udev configuration.


vmchannel
----------------------------------------------------------------------

Previous versions of libguestfs required something called "vmchannel".
Vmchannel is a special device given to virtual machines which allows
them to communicate in some way with the host, often (but not always)
without using a traditional network device.  In reality, there is no
one thing called "vmchannel".  This idea has been reimplemented
several times under the name vmchannel, and other hypervisors have
their own incompatible implementation(s) too.

In libguestfs <= 1.0.71, we required a specific vmchannel which is
properly known as "guestfwd" and has been upstream in qemu since here:

  http://lists.gnu.org/archive/html/qemu-devel/2009-02/msg01042.html

In libguestfs >= 1.0.71 we don't require any vmchannel implementation,
as long as qemu has been compiled with support for SLIRP (user mode
networking, or "-net user"), which is almost always the case.

In libguestfs >= 1.5.4 we switched again to using qemu's virtio-serial
and removed all the other vmchannels and the SLIRP channel.


Supermin appliance
----------------------------------------------------------------------

In libguestfs >= 1.7.19 the supermin appliance is the default and only
supported form of appliance.  For more information see febootstrap
(http://people.redhat.com/~rjones/febootstrap/).


Mirroring tip
----------------------------------------------------------------------

On my machines I can usually rebuild the appliance in around 3
minutes.  If it takes much longer for you, use a local Fedora mirror
or squid.

To use squid to cache yum downloads, read this first:
https://lists.dulug.duke.edu/pipermail/yum/2006-August/009041.html
(In brief, because yum chooses random mirrors each time, squid doesn't
work very well with default yum configuration.  To get around this,
choose a Fedora mirror which is close to you, set this with
'./configure --with-mirror=[...]', and then proxy the whole lot
through squid by setting http_proxy environment variable).

You will also need to substantially increase the squid configuration
limits:
http://fedoraproject.org/wiki/Using_Mock_to_test_package_builds#Using_Squid_to_Speed_Up_Mock_package_downloads


Porting to other Linux distros / non-Linux
----------------------------------------------------------------------

libguestfs itself should be fairly portable to other Linux
distributions.  Non-Linux ports are trickier, but we will accept
patches if they aren't too invasive.

The main porting issues are with the dependencies needed to build the
appliance.  You will need to port the febootstrap first
(http://people.redhat.com/~rjones/febootstrap/).


Copyright and license information
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Copyright (C) 2009-2010 Red Hat Inc.

The library is distributed under the LGPLv2+.  The programs are
distributed under the GPLv2+.  Please see the files COPYING and
COPYING.LIB for full license information.