NAME¶

guestfs-ruby - How to use libguestfs from Ruby

SYNOPSIS¶

 require 'guestfs'
 g = Guestfs::Guestfs.new()
 g.add_drive_opts("disk.img",
                  :readonly => 1, :format => "raw")
 g.launch()

DESCRIPTION¶

This manual page documents how to call libguestfs from the Ruby 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).

EXCEPTIONS¶

Errors from libguestfs functions are mapped into the "Error" exception. This has a single parameter which is the error message (a string).

EXAMPLE 1: CREATE A DISK IMAGE¶

 # Example showing how to create a disk image.
 
 require 'guestfs'
 
 output = "disk.img"
 
 g = Guestfs::Guestfs.new()
 
 # Create a raw-format sparse disk image, 512 MB in size.
 File.open(output, "w") {
   |f| f.truncate(512 * 1024 * 1024)
 }
 
 # 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")
 
 # 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.
 devices = g.list_devices()
 if devices.length != 1 then
   raise "error: expected a single device from list-devices"
 end
 
 # 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.
 partitions = g.list_partitions()
 if partitions.length != 1 then
   raise "error: expected a single partition from list-partitions"
 end
 
 # 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")
 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 close the handle
 # and the disk contents will be synchronized.  You can also do
 # this manually by calling g#umount_all and g#sync.
 g.close()

EXAMPLE 2: INSPECT A VIRTUAL MACHINE DISK IMAGE¶

 # Example showing how to inspect a virtual machine disk.
 
 require 'guestfs'
 
 if ARGV.length == 0
   puts "usage: inspect_vm disk.img"
   exit 1
 end
 disk = ARGV[0]
 
 g = Guestfs::Guestfs.new()
 
 # Attach the disk image read-only to libguestfs.
 g.add_drive_opts(disk, :readonly => 1)
 
 # Run the libguestfs back-end.
 g.launch()
 
 # Ask libguestfs to inspect for operating systems.
 roots = g.inspect_os()
 if roots.length == 0
   puts "inspect_vm: no operating systems found"
   exit 1
 end
 
 for root in roots do
   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.
   mps = g.inspect_get_mountpoints(root)
   mps = mps.sort {|a,b| a[0].length <=> b[0].length}
   for mp in mps do
     begin
       g.mount_ro(mp[1], mp[0])
     rescue Guestfs::Error => msg
       printf("%s (ignored)\n", msg)
     end
   end
 
   # If /etc/issue.net file exists, print up to 3 lines.
   filename = "/etc/issue.net"
   if g.is_file filename then
     printf("--- %s ---\n", filename)
     lines = g.head_n(3, filename)
     for line in lines do
       puts line
     end
   end
 
   # Unmount everything.
   g.umount_all()
 end

SEE ALSO¶

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

AUTHORS¶

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

COPYRIGHT¶

Copyright (C) 2010 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