guestfs-ruby3

Usage

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

Overview

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).

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.
 g.disk_create (output, "raw", 512 * 1024 * 1024)
 
 # Set the trace flag so that we can see each libguestfs call.
 g.set_trace(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(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 we wrote to the disk and we want to detect write
 # errors, call g.shutdown.  You don't need to do this:
 # g.close will do it implicitly.
 g.shutdown()
 
 # Note also that handles are automatically closed if they are
 # reaped by the garbage collector.  You only need to call close
 # if you want to close the handle right away.
 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 => true)
 
 # 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