Fix 'file(1)' command to work on /dev devices.

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

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# Copyright (C) 2009 Red Hat Inc.
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# This library is free software; you can redistribute it and/or
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# Lesser General Public License for more details.
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# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

=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 = $h->aug_ls ($path);

This is just a shortcut for listing C<$h-E<gt>aug_match>
C<path/*> and sorting the resulting nodes into alphabetical order.

=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 $h->chmod ($mode, $path);

Change the mode (permissions) of C<path> to C<mode>.  Only
numeric modes are supported.

=item $h->chown ($owner, $group, $path);

Change the file owner to C<owner> and group to C<group>.

Only numeric uid and gid are supported.  If you want to use
names, you will need to locate and parse the password file
yourself (Augeas support makes this relatively easy).

=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 $existsflag = $h->exists ($path);

This returns C<true> if and only if there is a file, directory
(or anything) with the given C<path> name.

See also C<$h-E<gt>is_file>, C<$h-E<gt>is_dir>, C<$h-E<gt>stat>.

=item $description = $h->file ($path);

This call uses the standard L<file(1)> command to determine
the type or contents of the file.  This also works on devices,
for example to find out whether a partition contains a filesystem.

The exact command which runs is C<file -bsL path>.  Note in
particular that the filename is not prepended to the output
(the C<-b> option).

=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 $dirflag = $h->is_dir ($path);

This returns C<true> if and only if there is a directory
with the given C<path> name.  Note that it returns false for
other objects like files.

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

=item $fileflag = $h->is_file ($path);

This returns C<true> if and only if there is a file
with the given C<path> name.  Note that it returns false for
other objects like directories.

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

=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 $h->lvcreate ($logvol, $volgroup, $mbytes);

This creates an LVM volume group called C<logvol>
on the volume group C<volgroup>, with C<size> megabytes.

=item $h->lvm_remove_all ();

This command removes all LVM logical volumes, volume groups
and physical volumes.

B<This command is dangerous.  Without careful use you
can easily destroy all your data>.

=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 $h->mkdir ($path);

Create a directory named C<path>.

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

Create a directory named C<path>, creating any parent directories
as necessary.  This is like the C<mkdir -p> shell command.

=item $h->mkfs ($fstype, $device);

This creates a filesystem on C<device> (usually a partition
of LVM logical volume).  The filesystem type is C<fstype>, for
example C<ext3>.

=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 @devices = $h->mounts ();

This returns the list of currently mounted filesystems.  It returns
the list of devices (eg. C</dev/sda1>, C</dev/VG/LV>).

Some internal mounts are not shown.

=item $h->pvcreate ($device);

This creates an LVM physical volume on the named C<device>,
where C<device> should usually be a partition name such
as C</dev/sda1>.

=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 $h->rm ($path);

Remove the single file C<path>.

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

Remove the file or directory C<path>, recursively removing the
contents if its a directory.  This is like the C<rm -rf> shell
command.

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

Remove the single directory C<path>.

=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 $h->sfdisk ($device, $cyls, $heads, $sectors, \@lines);

This is a direct interface to the L<sfdisk(8)> program for creating
partitions on block devices.

C<device> should be a block device, for example C</dev/sda>.

C<cyls>, C<heads> and C<sectors> are the number of cylinders, heads
and sectors on the device, which are passed directly to sfdisk as
the I<-C>, I<-H> and I<-S> parameters.  If you pass C<0> for any
of these, then the corresponding parameter is omitted.  Usually for
'large' disks, you can just pass C<0> for these, but for small
(floppy-sized) disks, sfdisk (or rather, the kernel) cannot work
out the right geometry and you will need to tell it.

C<lines> is a list of lines that we feed to C<sfdisk>.  For more
information refer to the L<sfdisk(8)> manpage.

To create a single partition occupying the whole disk, you would
pass C<lines> as a single element list, when the single element being
the string C<,> (comma).

B<This command is dangerous.  Without careful use you
can easily destroy all your data>.

=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 $h->umount ($pathordevice);

This unmounts the given filesystem.  The filesystem may be
specified either by its mountpoint (path) or the device which
contains the filesystem.

=item $h->umount_all ();

This unmounts all mounted filesystems.

Some internal mounts are not unmounted by this call.

=item $h->vgcreate ($volgroup, \@physvols);

This creates an LVM volume group called C<volgroup>
from the non-empty list of physical volumes C<physvols>.

=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.

=item $h->write_file ($path, $content, $size);

This call creates a file called C<path>.  The contents of the
file is the string C<content> (which can contain any 8 bit data),
with length C<size>.

As a special case, if C<size> is C<0>
then the length is calculated using C<strlen> (so in this case
the content cannot contain embedded ASCII NULs).

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

=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