[libguestfs.git] / perl / lib / Sys / Guestfs.pm

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# Copyright (C) 2009 Red Hat Inc.
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=pod

=head1 NAME

Sys::Guestfs - Perl bindings for libguestfs

=head1 SYNOPSIS

 use Sys::Guestfs;
 
 my $h = Sys::Guestfs->new ();
 $h->add_drive ('guest.img');
 $h->launch ();
 $h->wait_ready ();
 $h->mount ('/dev/sda1', '/');
 $h->touch ('/hello');
 $h->sync ();

=head1 DESCRIPTION

The C<Sys::Guestfs> module provides a Perl XS binding to the
libguestfs API for examining and modifying virtual machine
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 FTP.

=head1 ERRORS

All errors turn into calls to C<croak> (see L<Carp(3)>).

=head1 METHODS

=over 4

=cut

package Sys::Guestfs;

use strict;
use warnings;

require XSLoader;
XSLoader::load ('Sys::Guestfs');

=item $h = Sys::Guestfs->new ();

Create a new guestfs handle.

=cut

sub new {
  my $proto = shift;
  my $class = ref ($proto) || $proto;

  my $self = Sys::Guestfs::_create ();
  bless $self, $class;
  return $self;
}

=item $h->add_cdrom (filename);

This function adds a virtual CD-ROM disk image to the guest.

This is equivalent to the qemu parameter C<-cdrom filename>.

=item $h->add_drive (filename);

This function adds a virtual machine disk image C<filename> to the
guest.  The first time you call this function, the disk appears as IDE
disk 0 (C</dev/sda>) in the guest, the second time as C</dev/sdb>, and
so on.

You don't necessarily need to be root when using libguestfs.  However
you obviously do need sufficient permissions to access the filename
for whatever operations you want to perform (ie. read access if you
just want to read the image or write access if you want to modify the
image).

This is equivalent to the qemu parameter C<-drive file=filename>.

=item $h->aug_close ();

Close the current Augeas handle and free up any resources
used by it.  After calling this, you have to call
C<$h-E<gt>aug_init> again before you can use any other
Augeas functions.

=item ($nrnodes, $created) = $h->aug_defnode (name, expr, val);

Defines a variable C<name> whose value is the result of
evaluating C<expr>.

If C<expr> evaluates to an empty nodeset, a node is created,
equivalent to calling C<$h-E<gt>aug_set> C<expr>, C<value>.
C<name> will be the nodeset containing that single node.

On success this returns a pair containing the
number of nodes in the nodeset, and a boolean flag
if a node was created.

=item $nrnodes = $h->aug_defvar (name, expr);

Defines an Augeas variable C<name> whose value is the result
of evaluating C<expr>.  If C<expr> is NULL, then C<name> is
undefined.

On success this returns the number of nodes in C<expr>, or
C<0> if C<expr> evaluates to something which is not a nodeset.

=item $val = $h->aug_get (path);

Look up the value associated with C<path>.  If C<path>
matches exactly one node, the C<value> is returned.

=item $h->aug_init (root, flags);

Create a new Augeas handle for editing configuration files.
If there was any previous Augeas handle associated with this
guestfs session, then it is closed.

You must call this before using any other C<$h-E<gt>aug_*>
commands.

C<root> is the filesystem root.  C<root> must not be NULL,
use C</> instead.

The flags are the same as the flags defined in
E<lt>augeas.hE<gt>, the logical I<or> of the following
integers:

=over 4

=item C<AUG_SAVE_BACKUP> = 1

Keep the original file with a C<.augsave> extension.

=item C<AUG_SAVE_NEWFILE> = 2

Save changes into a file with extension C<.augnew>, and
do not overwrite original.  Overrides C<AUG_SAVE_BACKUP>.

=item C<AUG_TYPE_CHECK> = 4

Typecheck lenses (can be expensive).

=item C<AUG_NO_STDINC> = 8

Do not use standard load path for modules.

=item C<AUG_SAVE_NOOP> = 16

Make save a no-op, just record what would have been changed.

=item C<AUG_NO_LOAD> = 32

Do not load the tree in C<$h-E<gt>aug_init>.

=back

To close the handle, you can call C<$h-E<gt>aug_close>.

To find out more about Augeas, see L<http://augeas.net/>.

=item $h->aug_insert (path, label, before);

Create a new sibling C<label> for C<path>, inserting it into
the tree before or after C<path> (depending on the boolean
flag C<before>).

C<path> must match exactly one existing node in the tree, and
C<label> must be a label, ie. not contain C</>, C<*> or end
with a bracketed index C<[N]>.

=item $h->aug_load ();

Load files into the tree.

See C<aug_load> in the Augeas documentation for the full gory
details.

=item @matches = $h->aug_match (path);

Returns a list of paths which match the path expression C<path>.
The returned paths are sufficiently qualified so that they match
exactly one node in the current tree.

=item $h->aug_mv (src, dest);

Move the node C<src> to C<dest>.  C<src> must match exactly
one node.  C<dest> is overwritten if it exists.

=item $nrnodes = $h->aug_rm (path);

Remove C<path> and all of its children.

On success this returns the number of entries which were removed.

=item $h->aug_save ();

This writes all pending changes to disk.

The flags which were passed to C<$h-E<gt>aug_init> affect exactly
how files are saved.

=item $h->aug_set (path, val);

Set the value associated with C<path> to C<value>.

=item $content = $h->cat (path);

Return the contents of the file named C<path>.

Note that this function cannot correctly handle binary files
(specifically, files containing C<\0> character which is treated
as end of string).  For those you need to use the C<$h-E<gt>read_file>
function which has a more complex interface.

Because of the message protocol, there is a transfer limit 
of somewhere between 2MB and 4MB.  To transfer large files you should use
FTP.

=item $h->config (qemuparam, qemuvalue);

This can be used to add arbitrary qemu command line parameters
of the form C<-param value>.  Actually it's not quite arbitrary - we
prevent you from setting some parameters which would interfere with
parameters that we use.

The first character of C<param> string must be a C<-> (dash).

C<value> can be NULL.

=item $autosync = $h->get_autosync ();

Get the autosync flag.

=item $path = $h->get_path ();

Return the current search path.

This is always non-NULL.  If it wasn't set already, then this will
return the default path.

=item $verbose = $h->get_verbose ();

This returns the verbose messages flag.

=item $h->kill_subprocess ();

This kills the qemu subprocess.  You should never need to call this.

=item $h->launch ();

Internally libguestfs is implemented by running a virtual machine
using L<qemu(1)>.

You should call this after configuring the handle
(eg. adding drives) but before performing any actions.

=item @devices = $h->list_devices ();

List all the block devices.

The full block device names are returned, eg. C</dev/sda>

=item @partitions = $h->list_partitions ();

List all the partitions detected on all block devices.

The full partition device names are returned, eg. C</dev/sda1>

This does not return logical volumes.  For that you will need to
call C<$h-E<gt>lvs>.

=item $listing = $h->ll (directory);

List the files in C<directory> (relative to the root directory,
there is no cwd) in the format of 'ls -la'.

This command is mostly useful for interactive sessions.  It
is I<not> intended that you try to parse the output string.

=item @listing = $h->ls (directory);

List the files in C<directory> (relative to the root directory,
there is no cwd).  The '.' and '..' entries are not returned, but
hidden files are shown.

This command is mostly useful for interactive sessions.  Programs
should probably use C<$h-E<gt>readdir> instead.

=item @logvols = $h->lvs ();

List all the logical volumes detected.  This is the equivalent
of the L<lvs(8)> command.

This returns a list of the logical volume device names
(eg. C</dev/VolGroup00/LogVol00>).

See also C<$h-E<gt>lvs_full>.

=item @logvols = $h->lvs_full ();

List all the logical volumes detected.  This is the equivalent
of the L<lvs(8)> command.  The "full" version includes all fields.

=item $h->mount (device, mountpoint);

Mount a guest disk at a position in the filesystem.  Block devices
are named C</dev/sda>, C</dev/sdb> and so on, as they were added to
the guest.  If those block devices contain partitions, they will have
the usual names (eg. C</dev/sda1>).  Also LVM C</dev/VG/LV>-style
names can be used.

The rules are the same as for L<mount(2)>:  A filesystem must
first be mounted on C</> before others can be mounted.  Other
filesystems can only be mounted on directories which already
exist.

The mounted filesystem is writable, if we have sufficient permissions
on the underlying device.

The filesystem options C<sync> and C<noatime> are set with this
call, in order to improve reliability.

=item @physvols = $h->pvs ();

List all the physical volumes detected.  This is the equivalent
of the L<pvs(8)> command.

This returns a list of just the device names that contain
PVs (eg. C</dev/sda2>).

See also C<$h-E<gt>pvs_full>.

=item @physvols = $h->pvs_full ();

List all the physical volumes detected.  This is the equivalent
of the L<pvs(8)> command.  The "full" version includes all fields.

=item @lines = $h->read_lines (path);

Return the contents of the file named C<path>.

The file contents are returned as a list of lines.  Trailing
C<LF> and C<CRLF> character sequences are I<not> returned.

Note that this function cannot correctly handle binary files
(specifically, files containing C<\0> character which is treated
as end of line).  For those you need to use the C<$h-E<gt>read_file>
function which has a more complex interface.

=item $h->set_autosync (autosync);

If C<autosync> is true, this enables autosync.  Libguestfs will make a
best effort attempt to run C<$h-E<gt>sync> when the handle is closed
(also if the program exits without closing handles).

=item $h->set_path (path);

Set the path that libguestfs searches for kernel and initrd.img.

The default is C<$libdir/guestfs> unless overridden by setting
C<LIBGUESTFS_PATH> environment variable.

The string C<path> is stashed in the libguestfs handle, so the caller
must make sure it remains valid for the lifetime of the handle.

Setting C<path> to C<NULL> restores the default path.

=item $h->set_verbose (verbose);

If C<verbose> is true, this turns on verbose messages (to C<stderr>).

Verbose messages are disabled unless the environment variable
C<LIBGUESTFS_DEBUG> is defined and set to C<1>.

=item $h->sync ();

This syncs the disk, so that any writes are flushed through to the
underlying disk image.

You should always call this if you have modified a disk image, before
closing the handle.

=item $h->touch (path);

Touch acts like the L<touch(1)> command.  It can be used to
update the timestamps on a file, or, if the file does not exist,
to create a new zero-length file.

=item @volgroups = $h->vgs ();

List all the volumes groups detected.  This is the equivalent
of the L<vgs(8)> command.

This returns a list of just the volume group names that were
detected (eg. C<VolGroup00>).

See also C<$h-E<gt>vgs_full>.

=item @volgroups = $h->vgs_full ();

List all the volumes groups detected.  This is the equivalent
of the L<vgs(8)> command.  The "full" version includes all fields.

=item $h->wait_ready ();

Internally libguestfs is implemented by running a virtual machine
using L<qemu(1)>.

You should call this after C<$h-E<gt>launch> to wait for the launch
to complete.

=cut

1;

=back

=head1 COPYRIGHT

Copyright (C) 2009 Red Hat Inc.

=head1 LICENSE

Please see the file COPYING.LIB for the full license.

=head1 SEE ALSO

L<guestfs(3)>, L<guestfish(1)>.

=cut