Tip: Custom guestmount in Perl

Since libguestfs 1.18 guestmount has just been a slim wrapper around the libguestfs guestfs_mount_local API. You can replace guestmount with a small custom script if you want to do tricky/non-standard stuff like setting filesystem mount options, as in the example below.

$ ./mount-local.pl --ro -a /tmp/f17x64.img --mountopts=noatime /tmp/mount
mounting disk on /tmp/mount
to unmount: fusermount -u /tmp/mount

#!/usr/bin/perl -w

use strict;
use Getopt::Long;
use Sys::Guestfs;

my $readonly = 0;
my @drives;
my $mountopts;
my $trace = 0;

GetOptions ("ro|r" => \$readonly,
            "add|a=s" => \@drives,
            "mountopts=s" => \$mountopts,
            "trace|x" => \$trace)
    or die "$0 [--ro] [--add drive] [--mountopts mountopts] mountpoint\n";

die "$0: no drives (-a) were specified\n"
    unless @drives > 0;
die "$0: no mountpoint was specified\n"
    unless @ARGV == 1;

my $g = Sys::Guestfs->new ();
$g->set_trace (1) if $trace;
foreach (@drives) {
    $g->add_drive_opts ($_, readonly => $readonly)
}
$g->launch ();

# Inspect the disk to find OSes.
my @roots = $g->inspect_os ();
unless (@roots == 1) {
    die "$0: no operating systems found\n";
}
my $root = $roots[0];

# Mount up the disks like using the -i option.
my %mps = $g->inspect_get_mountpoints ($root);
my @mps = sort { length $a <=> length $b } (keys %mps);
foreach (@mps) {
    my $options = $readonly ? "ro" : "rw";
    $options .= "," . $mountopts if defined $mountopts;
    eval { $g->mount_options ($options, $mps{$_}, $_) };
    if ($@) {
        print "$@ (ignored)\n"
    }
}

# Export the filesystem using FUSE.
$g->mount_local ($ARGV[0]);

print "mounting disk on $ARGV[0]\n";
print "to unmount: fusermount -u $ARGV[0]\n";
$g->mount_local_run ();
# This returns when the filesystem is unmounted.

$g->shutdown ();
$g->close ();