NAME¶

guestfs-lua - How to use libguestfs from Lua

SYNOPSIS¶

 local G = require "guestfs"
 g = G.create ()
 g:add_drive ("test.img", { format = "raw", readonly = true })
 g:launch ()
 devices = g:list_devices ()
 g:close ()

DESCRIPTION¶

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

 local G = require "guestfs"

 g = G.create ()

 g = G.create { environment = 0, close_on_exit = 0 }

 g:close ()

 g:set_verbose (true)

 g:add_drive ("test.img")

 g:add_drive ("test.img", { format = "raw", readonly = true })

 eh = g:set_event_callback (cb, "close")

 eh = g:set_event_callback (cb, { "appliance", "library", "trace" })

 function cb (g, event, eh, flags, buf, array)
   -- g is the guestfs handle
   -- event is a string which is the name of the event that fired
   -- flags is always zero
   -- buf is the data buffer (eg. log message etc)
   -- array is the array of 64 bit ints (eg. progress bar status etc)
   ...
 end

 g:delete_event_callback (eh)

EXAMPLE 1: CREATE A DISK IMAGE¶

 -- Example showing how to create a disk image.
 
 local G = require "guestfs"
 
 local output = "disk.img"
 
 local g = G.create ()
 
 -- Create a raw-format sparse disk image, 512 MB in size.
 file = io.open (output, "w")
 file:seek ("set", 512 * 1024 * 1024)
 file:write (' ')
 file:close ()
 
 -- Set the trace flag so that we can see each libguestfs call.
 g:set_trace (true)
 
 -- Attach the disk image to libguestfs.
 g:add_drive (output, { format = "raw", readonly = false })
 
 -- 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 table.getn (devices) ~= 1 then
    error "expected a single device from list-devices"
 end
 
 -- Partition the disk as one single MBR partition.
 g:part_disk (devices[1], "mbr")
 
 -- Get the list of partitions.  We expect a single element, which
 -- is the partition we have just created.
 partitions = g:list_partitions ()
 if table.getn (partitions) ~= 1 then
    error "expected a single partition from list-partitions"
 end
 
 -- Create a filesystem on the partition.
 g:mkfs ("ext4", partitions[1])
 
 -- Now mount the filesystem so that we can add files.
 g:mount (partitions[1], "/")
 
 -- 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.
 
 local G = require "guestfs"
 
 if table.getn (arg) == 1 then
    disk = arg[1]
 else
    error ("usage: inspect_vm disk.img")
 end
 
 local g = G.create ()
 
 -- Attach the disk image read-only to libguestfs.
 g:add_drive (disk, { -- format:"raw"
                      readonly = true })
 
 -- Run the libguestfs back-end.
 g:launch ()
 
 -- Ask libguestfs to inspect for operating systems.
 local roots = g:inspect_os ()
 if table.getn (roots) == 0 then
    error ("inspect_vm: no operating systems found")
 end
 
 for _, root in ipairs (roots) do
    print ("Root device: ", root)
 
    -- Print basic information about the operating system.
    print ("  Product name: ", g:inspect_get_product_name (root))
    print ("  Version:      ",
           g:inspect_get_major_version (root),
           g:inspect_get_minor_version (root))
    print ("  Type:         ", g:inspect_get_type (root))
    print ("  Distro:       ", 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)
    table.sort (mps,
                function (a, b)
                   return string.len (a) < string.len (b)
                end)
    for mp,dev in pairs (mps) do
       pcall (function () g:mount_ro (dev, mp) end)
    end
 
    -- If /etc/issue.net file exists, print up to 3 lines.
    filename = "/etc/issue.net"
    if g:is_file (filename) then
       print ("--- ", filename, " ---")
       lines = g:head_n (3, filename)
       for _, line in ipairs (lines) do
          print (line)
       end
    end
 
    -- Unmount everything.
    g:umount_all ()
 end

SEE ALSO¶

guestfs(3), guestfs-examples(3), guestfs-erlang(3), guestfs-gobject(3), guestfs-golang(3), guestfs-java(3), guestfs-ocaml(3), guestfs-perl(3), guestfs-python(3), guestfs-recipes(1), guestfs-ruby(3), http://www.lua.org/, http://libguestfs.org/.

AUTHORS¶

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

COPYRIGHT¶

Copyright (C) 2012 Red Hat Inc.

LICENSE¶

This manual page contains examples which we hope you will use in your programs. The examples may be freely copied, modified and distributed for any purpose without any restrictions.

BUGS¶

To get a list of bugs against libguestfs, use this link: https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools

To report a new bug against libguestfs, use this link: https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools

When reporting a bug, please supply:

• The version of libguestfs.
• Where you got libguestfs (eg. which Linux distro, compiled from source, etc)
• Describe the bug accurately and give a way to reproduce it.
• Run libguestfs-test-tool(1) and paste the complete, unedited output into the bug report.