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.\" ========================================================================
.\"
.IX Title "guestfs-lua 3"
.TH guestfs-lua 3 2024-01-05 libguestfs-1.52.0 "Virtualization Support"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
guestfs\-lua \- How to use libguestfs from Lua
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 6
\& local G = require "guestfs"
\& g = G.create ()
\& g:add_drive ("test.img", { format = "raw", readonly = true })
\& g:launch ()
\& devices = g:list_devices ()
\& g:close ()
.Ve
.SH DESCRIPTION
.IX Header "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 \fBguestfs\fR\|(3).
.SS "REQUIRING THE MODULE"
.IX Subsection "REQUIRING THE MODULE"
\&\f(CW\*(C`require "guestfs"\*(C'\fR returns the module, so you have to assign it
to a local variable.  Typical usage is:
.PP
.Vb 1
\& local G = require "guestfs"
.Ve
.PP
(you can use any name you want instead of \f(CW\*(C`G\*(C'\fR, but in the examples
in this man page we always use \f(CW\*(C`G\*(C'\fR).
.SS "OPENING AND CLOSING THE HANDLE"
.IX Subsection "OPENING AND CLOSING THE HANDLE"
To create a new handle, call:
.PP
.Vb 1
\& g = G.create ()
.Ve
.PP
You can also use the optional arguments:
.PP
.Vb 1
\& g = G.create { environment = 0, close_on_exit = 0 }
.Ve
.PP
to set the flags \f(CW\*(C`GUESTFS_CREATE_NO_ENVIRONMENT\*(C'\fR
and/or \f(CW\*(C`GUESTFS_CREATE_NO_CLOSE_ON_EXIT\*(C'\fR.
.PP
The handle will be closed by the garbage collector, but you can
also close it explicitly by doing:
.PP
.Vb 1
\& g:close ()
.Ve
.SS "CALLING METHODS"
.IX Subsection "CALLING METHODS"
Use the ordinary Lua convention for calling methods on the handle.
For example:
.PP
.Vb 1
\& g:set_verbose (true)
.Ve
.SS "FUNCTIONS WITH OPTIONAL ARGUMENTS"
.IX Subsection "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.
.PP
.Vb 1
\& g:add_drive ("test.img")
.Ve
.PP
or:
.PP
.Vb 1
\& g:add_drive ("test.img", { format = "raw", readonly = true })
.Ve
.SS "64 BIT VALUES"
.IX Subsection "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.
.SS ERRORS
.IX Subsection "ERRORS"
Most (but not all) errors are converted into objects (ie. tables)
containing the following fields:
.IP msg 4
.IX Item "msg"
The error message (corresponding to "guestfs_last_error" in \fBguestfs\fR\|(3)).
.IP code 4
.IX Item "code"
The \f(CW\*(C`errno\*(C'\fR (corresponding to "guestfs_last_errno" in \fBguestfs\fR\|(3)).
.PP
These objects also have \f(CW\*(C`_\|_tostring\*(C'\fR functions attached to them
so you can use \f(CW\*(C`tostring\*(C'\fR (or implicit conversion) to convert them
into printable strings.
.PP
Note that the library also throws some errors as plain strings.  You
may need to check the type.
.SS EVENTS
.IX Subsection "EVENTS"
Events can be registered by calling \f(CW\*(C`set_event_callback\*(C'\fR:
.PP
.Vb 1
\& eh = g:set_event_callback (cb, "close")
.Ve
.PP
or to register a single callback for multiple events make the
second argument a list:
.PP
.Vb 1
\& eh = g:set_event_callback (cb, { "appliance", "library", "trace" })
.Ve
.PP
A list of all valid event types (strings) is in the global variable
\&\f(CW\*(C`G.event_all\*(C'\fR.
.PP
The callback (\f(CW\*(C`cb\*(C'\fR) is called with the following parameters:
.PP
.Vb 8
\& 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
.Ve
.PP
You can also remove a callback using the event handle (\f(CW\*(C`eh\*(C'\fR) that was
returned when you registered the callback:
.PP
.Vb 1
\& g:delete_event_callback (eh)
.Ve
.SH "EXAMPLE 1: CREATE A DISK IMAGE"
.IX Header "EXAMPLE 1: CREATE A DISK IMAGE"
.Vb 1
\& \-\- 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 (\*(Aq \*(Aq)
\& 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\en"
\& 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\*(Aqt 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 ()
.Ve
.SH "EXAMPLE 2: INSPECT A VIRTUAL MACHINE DISK IMAGE"
.IX Header "EXAMPLE 2: INSPECT A VIRTUAL MACHINE DISK IMAGE"
.Vb 1
\& \-\- 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
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBguestfs\fR\|(3),
\&\fBguestfs\-examples\fR\|(3),
\&\fBguestfs\-erlang\fR\|(3),
\&\fBguestfs\-gobject\fR\|(3),
\&\fBguestfs\-golang\fR\|(3),
\&\fBguestfs\-java\fR\|(3),
\&\fBguestfs\-ocaml\fR\|(3),
\&\fBguestfs\-perl\fR\|(3),
\&\fBguestfs\-python\fR\|(3),
\&\fBguestfs\-recipes\fR\|(1),
\&\fBguestfs\-ruby\fR\|(3),
http://www.lua.org/,
http://libguestfs.org/.
.SH AUTHORS
.IX Header "AUTHORS"
Richard W.M. Jones (\f(CW\*(C`rjones at redhat dot com\*(C'\fR)
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (C) 2012 Red Hat Inc.
.SH LICENSE
.IX Header "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.
.SH BUGS
.IX Header "BUGS"
To get a list of bugs against libguestfs, use this link:
https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
.PP
To report a new bug against libguestfs, use this link:
https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
.PP
When reporting a bug, please supply:
.IP \(bu 4
The version of libguestfs.
.IP \(bu 4
Where you got libguestfs (eg. which Linux distro, compiled from source, etc)
.IP \(bu 4
Describe the bug accurately and give a way to reproduce it.
.IP \(bu 4
Run \fBlibguestfs\-test\-tool\fR\|(1) and paste the \fBcomplete, unedited\fR
output into the bug report.