Unix/Linux Go Back    


CentOS 7.0 - man page for guestfs-lua (centos section 3)

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


guestfs-lua(3)			      Virtualization Support			   guestfs-lua(3)

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).

   REQUIRING THE MODULE
       "require "guestfs"" returns the module, so you have to assign it to a local variable.
       Typical usage is:

	local G = require "guestfs"

       (you can use any name you want instead of "G", but in the examples in this man page we
       always use "G").

   OPENING AND CLOSING THE HANDLE
       To create a new handle, call:

	g = G.create ()

       You can also use the optional arguments:

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

       to set the flags "GUESTFS_CREATE_NO_ENVIRONMENT" and/or "GUESTFS_CREATE_NO_CLOSE_ON_EXIT".

       The handle will be closed by the garbage collector, but you can also close it explicitly
       by doing:

	g:close ()

   CALLING METHODS
       Use the ordinary Lua convention for calling methods on the handle.  For example:

	g:set_verbose (true)

   FUNCTIONS WITH OPTIONAL ARGUMENTS
       For functions that take optional arguments, the first arguments are the non-optional ones.
       The optional final argument is a table supplying the optional arguments.

	g:add_drive ("test.img")

       or:

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

   64 BIT VALUES
       Currently 64 bit values must be passed as strings, and are returned as strings.	This is
       because 32 bit Lua cannot handle 64 bit integers properly.  We hope to come up with a
       better solution later.

   ERRORS
       Most (but not all) errors are converted into objects (ie. tables) containing the following
       fields:

       msg The error message (corresponding to "guestfs_last_error" in guestfs(3)).

       code
	   The "errno" (corresponding to "guestfs_last_errno" in guestfs(3)).

       These objects also have "__tostring" functions attached to them so you can use "tostring"
       (or implicit conversion) to convert them into printable strings.

       Note that the library also throws some errors as plain strings.	You may need to check the
       type.

   EVENTS
       Events can be registered by calling "set_event_callback":

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

       or to register a single callback for multiple events make the second argument a list:

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

       A list of all valid event types (strings) is in the global variable "G.event_all".

       The callback ("cb") is called with the following parameters:

	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

       You can also remove a callback using the event handle ("eh") that was returned when you
       registered the callback:

	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-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:

       o   The version of libguestfs.

       o   Where you got libguestfs (eg. which Linux distro, compiled from source, etc)

       o   Describe the bug accurately and give a way to reproduce it.

       o   Run libguestfs-test-tool(1) and paste the complete, unedited output into the bug
	   report.

libguestfs-1.22.6			    2013-08-24				   guestfs-lua(3)
Unix & Linux Commands & Man Pages : ©2000 - 2018 Unix and Linux Forums


All times are GMT -4. The time now is 04:12 PM.