NAME¶

guestfs-perl - How to use libguestfs from Perl

SYNOPSIS¶

 use Sys::Guestfs;
 
 my $h = Sys::Guestfs->new ();
 $h->add_drive_opts ('guest.img', format => 'raw');
 $h->launch ();
 $h->mount_options ('', '/dev/sda1', '/');
 $h->touch ('/hello');
 $h->sync ();

DESCRIPTION¶

This manual page documents how to call libguestfs from the Perl programming language. This page just documents the differences from the C API and gives some examples. If you are not familiar with using libguestfs, you also need to read guestfs(3). To read the full Perl API, see Sys::Guestfs(3).

ERRORS¶

Errors from libguestfs functions turn into calls to "croak" (see Carp(3)).

EXAMPLE 1: CREATE A DISK IMAGE¶

 #!/usr/bin/perl -w
 
 # Example showing how to create a disk image.
 
 use strict;
 use Sys::Guestfs;
 
 my $output = "disk.img";
 
 my $g = new Sys::Guestfs ();
 
 # Create a raw-format sparse disk image, 512 MB in size.
 open FILE, ">$output" or die "$output: $!";
 truncate FILE, 512 * 1024 * 1024 or die "$output: truncate: $!";
 close FILE or die "$output: $!";
 
 # Set the trace flag so that we can see each libguestfs call.
 $g->set_trace (1);
 
 # Set the autosync flag so that the disk will be synchronized
 # automatically when the libguestfs handle is closed.
 $g->set_autosync (1);
 
 # Attach the disk image to libguestfs.
 $g->add_drive_opts ($output, format => "raw", readonly => 0);
 
 # Run the libguestfs back-end.
 $g->launch ();
 
 # Get the list of devices.  Because we only added one drive
 # above, we expect that this list should contain a single
 # element.
 my @devices = $g->list_devices ();
 if (@devices != 1) {
     die "error: expected a single device from list-devices";
 }
 
 # Partition the disk as one single MBR partition.
 $g->part_disk ($devices[0], "mbr");
 
 # Get the list of partitions.  We expect a single element, which
 # is the partition we have just created.
 my @partitions = $g->list_partitions ();
 if (@partitions != 1) {
     die "error: expected a single partition from list-partitions";
 }
 
 # Create a filesystem on the partition.
 $g->mkfs ("ext4", $partitions[0]);
 
 # Now mount the filesystem so that we can add files.
 $g->mount_options ("", $partitions[0], "/");
 
 # Create some files and directories.
 $g->touch ("/empty");
 my $message = "Hello, world\n";
 $g->write ("/hello", $message);
 $g->mkdir ("/foo");
 
 # This one uploads the local file /etc/resolv.conf into
 # the disk image.
 $g->upload ("/etc/resolv.conf", "/foo/resolv.conf");
 
 # Because 'autosync' was set (above) we can just exit here
 # and the disk contents will be synchronized.  You can also do
 # this manually by calling $g->umount_all and $g->sync.
 exit 0

EXAMPLE 2: INSPECT A VIRTUAL MACHINE DISK IMAGE¶

 #!/usr/bin/perl -w
 
 # Example showing how to inspect a virtual machine disk.
 
 use strict;
 use Sys::Guestfs;
 
 if (@ARGV < 1) {
     die "usage: inspect_vm disk.img"
 }
 
 my $disk = $ARGV[0];
 
 my $g = new Sys::Guestfs ();
 
 # Attach the disk image read-only to libguestfs.
 # You could also add an optional format => ... argument here.  This is
 # advisable since automatic format detection is insecure.
 $g->add_drive_opts ($disk, readonly => 1);
 
 # Run the libguestfs back-end.
 $g->launch ();
 
 # Ask libguestfs to inspect for operating systems.
 my @roots = $g->inspect_os ();
 if (@roots == 0) {
     die "inspect_vm: no operating systems found";
 }
 
 for my $root (@roots) {
     printf "Root device: %s\n", $root;
 
     # Print basic information about the operating system.
     printf "  Product name: %s\n", $g->inspect_get_product_name ($root);
     printf "  Version:      %d.%d\n",
         $g->inspect_get_major_version ($root),
         $g->inspect_get_minor_version ($root);
     printf "  Type:         %s\n", $g->inspect_get_type ($root);
     printf "  Distro:       %s\n", $g->inspect_get_distro ($root);
 
     # Mount up the disks, like guestfish -i.
     #
     # Sort keys by length, shortest first, so that we end up
     # mounting the filesystems in the correct order.
     my %mps = $g->inspect_get_mountpoints ($root);
     my @mps = sort { length $a <=> length $b } (keys %mps);
     for my $mp (@mps) {
         eval { $g->mount_ro ($mps{$mp}, $mp) };
         if ($@) {
             print "$@ (ignored)\n"
         }
     }
 
     # If /etc/issue.net file exists, print up to 3 lines.
     my $filename = "/etc/issue.net";
     if ($g->is_file ($filename)) {
         printf "--- %s ---\n", $filename;
         my @lines = $g->head_n (3, $filename);
         print "$_\n" foreach @lines;
     }
 
     # Unmount everything.
     $g->umount_all ()
 }

SEE ALSO¶

Sys::Guestfs(3), guestfs(3), guestfs-examples(3), guestfs-erlang(3), guestfs-java(3), guestfs-ocaml(3), guestfs-python(3), guestfs-recipes(1), guestfs-ruby(3), <http://libguestfs.org/>.

AUTHORS¶

Richard W.M. Jones ("rjones at redhat dot com")

COPYRIGHT¶

Copyright (C) 2011 Red Hat Inc. <http://libguestfs.org/> The examples in this manual page may be freely copied, modified and distributed without any restrictions. This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA