1guestfs-lua(3) Virtualization Support guestfs-lua(3)
2
3
4
6 guestfs-lua - How to use libguestfs from Lua
7
9 local G = require "guestfs"
10 g = G.create ()
11 g:add_drive ("test.img", { format = "raw", readonly = true })
12 g:launch ()
13 devices = g:list_devices ()
14 g:close ()
15
17 This manual page documents how to call libguestfs from the Lua
18 programming language. This page just documents the differences from
19 the C API and gives some examples. If you are not familiar with using
20 libguestfs, you also need to read guestfs(3).
21
22 REQUIRING THE MODULE
23 "require "guestfs"" returns the module, so you have to assign it to a
24 local variable. Typical usage is:
25
26 local G = require "guestfs"
27
28 (you can use any name you want instead of "G", but in the examples in
29 this man page we always use "G").
30
31 OPENING AND CLOSING THE HANDLE
32 To create a new handle, call:
33
34 g = G.create ()
35
36 You can also use the optional arguments:
37
38 g = G.create { environment = 0, close_on_exit = 0 }
39
40 to set the flags "GUESTFS_CREATE_NO_ENVIRONMENT" and/or
41 "GUESTFS_CREATE_NO_CLOSE_ON_EXIT".
42
43 The handle will be closed by the garbage collector, but you can also
44 close it explicitly by doing:
45
46 g:close ()
47
48 CALLING METHODS
49 Use the ordinary Lua convention for calling methods on the handle. For
50 example:
51
52 g:set_verbose (true)
53
54 FUNCTIONS WITH OPTIONAL ARGUMENTS
55 For functions that take optional arguments, the first arguments are the
56 non-optional ones. The optional final argument is a table supplying
57 the optional arguments.
58
59 g:add_drive ("test.img")
60
61 or:
62
63 g:add_drive ("test.img", { format = "raw", readonly = true })
64
65 64 BIT VALUES
66 Currently 64 bit values must be passed as strings, and are returned as
67 strings. This is because 32 bit Lua cannot handle 64 bit integers
68 properly. We hope to come up with a better solution later.
69
70 ERRORS
71 Most (but not all) errors are converted into objects (ie. tables)
72 containing the following fields:
73
74 msg The error message (corresponding to "guestfs_last_error" in
75 guestfs(3)).
76
77 code
78 The "errno" (corresponding to "guestfs_last_errno" in guestfs(3)).
79
80 These objects also have "__tostring" functions attached to them so you
81 can use "tostring" (or implicit conversion) to convert them into
82 printable strings.
83
84 Note that the library also throws some errors as plain strings. You
85 may need to check the type.
86
87 EVENTS
88 Events can be registered by calling "set_event_callback":
89
90 eh = g:set_event_callback (cb, "close")
91
92 or to register a single callback for multiple events make the second
93 argument a list:
94
95 eh = g:set_event_callback (cb, { "appliance", "library", "trace" })
96
97 A list of all valid event types (strings) is in the global variable
98 "G.event_all".
99
100 The callback ("cb") is called with the following parameters:
101
102 function cb (g, event, eh, flags, buf, array)
103 -- g is the guestfs handle
104 -- event is a string which is the name of the event that fired
105 -- flags is always zero
106 -- buf is the data buffer (eg. log message etc)
107 -- array is the array of 64 bit ints (eg. progress bar status etc)
108 ...
109 end
110
111 You can also remove a callback using the event handle ("eh") that was
112 returned when you registered the callback:
113
114 g:delete_event_callback (eh)
115
117 -- Example showing how to create a disk image.
118
119 local G = require "guestfs"
120
121 local output = "disk.img"
122
123 local g = G.create ()
124
125 -- Create a raw-format sparse disk image, 512 MB in size.
126 file = io.open (output, "w")
127 file:seek ("set", 512 * 1024 * 1024)
128 file:write (' ')
129 file:close ()
130
131 -- Set the trace flag so that we can see each libguestfs call.
132 g:set_trace (true)
133
134 -- Attach the disk image to libguestfs.
135 g:add_drive (output, { format = "raw", readonly = false })
136
137 -- Run the libguestfs back-end.
138 g:launch ()
139
140 -- Get the list of devices. Because we only added one drive
141 -- above, we expect that this list should contain a single
142 -- element.
143 devices = g:list_devices ()
144 if table.getn (devices) ~= 1 then
145 error "expected a single device from list-devices"
146 end
147
148 -- Partition the disk as one single MBR partition.
149 g:part_disk (devices[1], "mbr")
150
151 -- Get the list of partitions. We expect a single element, which
152 -- is the partition we have just created.
153 partitions = g:list_partitions ()
154 if table.getn (partitions) ~= 1 then
155 error "expected a single partition from list-partitions"
156 end
157
158 -- Create a filesystem on the partition.
159 g:mkfs ("ext4", partitions[1])
160
161 -- Now mount the filesystem so that we can add files.
162 g:mount (partitions[1], "/")
163
164 -- Create some files and directories.
165 g:touch ("/empty")
166 message = "Hello, world\n"
167 g:write ("/hello", message)
168 g:mkdir ("/foo")
169
170 -- This one uploads the local file /etc/resolv.conf into
171 -- the disk image.
172 g:upload ("/etc/resolv.conf", "/foo/resolv.conf")
173
174 -- Because we wrote to the disk and we want to detect write
175 -- errors, call g:shutdown. You don't need to do this:
176 -- g:close will do it implicitly.
177 g:shutdown ()
178
179 -- Note also that handles are automatically closed if they are
180 -- reaped by the garbage collector. You only need to call close
181 -- if you want to close the handle right away.
182 g:close ()
183
185 -- Example showing how to inspect a virtual machine disk.
186
187 local G = require "guestfs"
188
189 if table.getn (arg) == 1 then
190 disk = arg[1]
191 else
192 error ("usage: inspect_vm disk.img")
193 end
194
195 local g = G.create ()
196
197 -- Attach the disk image read-only to libguestfs.
198 g:add_drive (disk, { -- format:"raw"
199 readonly = true })
200
201 -- Run the libguestfs back-end.
202 g:launch ()
203
204 -- Ask libguestfs to inspect for operating systems.
205 local roots = g:inspect_os ()
206 if table.getn (roots) == 0 then
207 error ("inspect_vm: no operating systems found")
208 end
209
210 for _, root in ipairs (roots) do
211 print ("Root device: ", root)
212
213 -- Print basic information about the operating system.
214 print (" Product name: ", g:inspect_get_product_name (root))
215 print (" Version: ",
216 g:inspect_get_major_version (root),
217 g:inspect_get_minor_version (root))
218 print (" Type: ", g:inspect_get_type (root))
219 print (" Distro: ", g:inspect_get_distro (root))
220
221 -- Mount up the disks, like guestfish -i.
222 --
223 -- Sort keys by length, shortest first, so that we end up
224 -- mounting the filesystems in the correct order.
225 mps = g:inspect_get_mountpoints (root)
226 table.sort (mps,
227 function (a, b)
228 return string.len (a) < string.len (b)
229 end)
230 for mp,dev in pairs (mps) do
231 pcall (function () g:mount_ro (dev, mp) end)
232 end
233
234 -- If /etc/issue.net file exists, print up to 3 lines.
235 filename = "/etc/issue.net"
236 if g:is_file (filename) then
237 print ("--- ", filename, " ---")
238 lines = g:head_n (3, filename)
239 for _, line in ipairs (lines) do
240 print (line)
241 end
242 end
243
244 -- Unmount everything.
245 g:umount_all ()
246 end
247
249 guestfs(3), guestfs-examples(3), guestfs-erlang(3), guestfs-gobject(3),
250 guestfs-golang(3), guestfs-java(3), guestfs-ocaml(3), guestfs-perl(3),
251 guestfs-python(3), guestfs-recipes(1), guestfs-ruby(3),
252 http://www.lua.org/, http://libguestfs.org/.
253
255 Richard W.M. Jones ("rjones at redhat dot com")
256
258 Copyright (C) 2012 Red Hat Inc.
259
261 This manual page contains examples which we hope you will use in your
262 programs. The examples may be freely copied, modified and distributed
263 for any purpose without any restrictions.
264
266 To get a list of bugs against libguestfs, use this link:
267 https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
268
269 To report a new bug against libguestfs, use this link:
270 https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
271
272 When reporting a bug, please supply:
273
274 · The version of libguestfs.
275
276 · Where you got libguestfs (eg. which Linux distro, compiled from
277 source, etc)
278
279 · Describe the bug accurately and give a way to reproduce it.
280
281 · Run libguestfs-test-tool(1) and paste the complete, unedited output
282 into the bug report.
283
284
285
286libguestfs-1.40.2 2019-02-07 guestfs-lua(3)