1guestfs-ocaml(3) Virtualization Support guestfs-ocaml(3)
2
6 guestfs-ocaml - How to use libguestfs from OCaml
7
9 Module style:
10 let g = Guestfs.create () in
12 Guestfs.add_drive_opts g ~format:"raw" ~readonly:true "disk.img";
13 Guestfs.launch g;
14 Object-oriented style:
16 let g = new Guestfs.guestfs () in
18 g#add_drive_opts ~format:"raw" ~readonly:true "disk.img";
19 g#launch ();
20 ocamlfind opt prog.ml -package guestfs -linkpkg -o prog
22 or:
23 ocamlopt -I +guestfs mlguestfs.cmxa prog.ml -o prog
24
26 This manual page documents how to call libguestfs from the OCaml
27 programming language. This page just documents the differences from
28 the C API and gives some examples. If you are not familiar with using
29 libguestfs, you also need to read guestfs(3).
30 PROGRAMMING STYLES
32 There are two different programming styles supported by the OCaml
33 bindings. You can use a module style, with each C function mapped to
34 an OCaml function:
35 int guestfs_set_verbose (guestfs_h *g, int flag);
37 becomes:
39 val Guestfs.set_verbose : Guestfs.t -> bool -> unit
41 Alternately you can use an object-oriented style, calling methods on
43 the class "Guestfs.guestfs":
44 method set_verbose : bool -> unit
46 The object-oriented style is usually briefer, and the minor performance
48 penalty isn't noticable in the general overhead of performing
49 libguestfs functions.
50 CLOSING THE HANDLE
52 The handle is closed when it is reaped by the garbage collector.
53 Because libguestfs handles include a lot of state, it is also possible
54 to close (and hence free) them explicitly by calling "Guestfs.close" or
55 the "#close" method.
56 EXCEPTIONS
58 Errors from libguestfs functions are mapped into the "Guestfs.Error"
59 exception. This has a single parameter which is the error message (a
60 string).
61 Calling any function/method on a closed handle raises
63 "Guestfs.Handle_closed". The single parameter is the name of the
64 function that you called.
65
67 (* Example showing how to create a disk image. *)
68 open Unix
70 open Printf
71 let output = "disk.img"
73 let () =
75 let g = new Guestfs.guestfs () in
76 (* Create a raw-format sparse disk image, 512 MB in size. *)
78 let fd = openfile output [O_WRONLY;O_CREAT;O_TRUNC;O_NOCTTY] 0o666 in
79 ftruncate fd (512 * 1024 * 1024);
80 close fd;
81 (* Set the trace flag so that we can see each libguestfs call. *)
83 g#set_trace true;
84 (* Set the autosync flag so that the disk will be synchronized
86 * automatically when the libguestfs handle is closed.
87 *)
88 g#set_autosync true;
89 (* Attach the disk image to libguestfs. *)
91 g#add_drive_opts ~format:"raw" ~readonly:false output;
92 (* Run the libguestfs back-end. *)
94 g#launch ();
95 (* Get the list of devices. Because we only added one drive
97 * above, we expect that this list should contain a single
98 * element.
99 *)
100 let devices = g#list_devices () in
101 if Array.length devices <> 1 then
102 failwith "error: expected a single device from list-devices";
103 (* Partition the disk as one single MBR partition. *)
105 g#part_disk devices.(0) "mbr";
106 (* Get the list of partitions. We expect a single element, which
108 * is the partition we have just created.
109 *)
110 let partitions = g#list_partitions () in
111 if Array.length partitions <> 1 then
112 failwith "error: expected a single partition from list-partitions";
113 (* Create a filesystem on the partition. *)
115 g#mkfs "ext4" partitions.(0);
116 (* Now mount the filesystem so that we can add files. *)
118 g#mount_options "" partitions.(0) "/";
119 (* Create some files and directories. *)
121 g#touch "/empty";
122 let message = "Hello, world\n" in
123 g#write "/hello" message;
124 g#mkdir "/foo";
125 (* This one uploads the local file /etc/resolv.conf into
127 * the disk image.
128 *)
129 g#upload "/etc/resolv.conf" "/foo/resolv.conf";
130 (* Because 'autosync' was set (above) we can just close the handle
132 * and the disk contents will be synchronized. You can also do
133 * this manually by calling g#umount_all and g#sync.
134 *
135 * Note also that handles are automatically closed if they are
136 * reaped by the garbage collector. You only need to call close
137 * if you want to close the handle right away.
138 *)
139 g#close ()
140
142 (* Example showing how to inspect a virtual machine disk. *)
143 open Printf
145 let disk =
147 if Array.length Sys.argv = 2 then
148 Sys.argv.(1)
149 else
150 failwith "usage: inspect_vm disk.img"
151 let () =
153 let g = new Guestfs.guestfs () in
154 (* Attach the disk image read-only to libguestfs. *)
156 g#add_drive_opts (*~format:"raw"*) ~readonly:true disk;
157 (* Run the libguestfs back-end. *)
159 g#launch ();
160 (* Ask libguestfs to inspect for operating systems. *)
162 let roots = g#inspect_os () in
163 if Array.length roots = 0 then
164 failwith "inspect_vm: no operating systems found";
165 Array.iter (
167 fun root ->
168 printf "Root device: %s\n" root;
169 (* Print basic information about the operating system. *)
171 printf " Product name: %s\n" (g#inspect_get_product_name root);
172 printf " Version: %d.%d\n"
173 (g#inspect_get_major_version root)
174 (g#inspect_get_minor_version root);
175 printf " Type: %s\n" (g#inspect_get_type root);
176 printf " Distro: %s\n" (g#inspect_get_distro root);
177 (* Mount up the disks, like guestfish -i.
179 *
180 * Sort keys by length, shortest first, so that we end up
181 * mounting the filesystems in the correct order.
182 *)
183 let mps = g#inspect_get_mountpoints root in
184 let cmp (a,_) (b,_) =
185 compare (String.length a) (String.length b) in
186 let mps = List.sort cmp mps in
187 List.iter (
188 fun (mp, dev) ->
189 try g#mount_ro dev mp
190 with Guestfs.Error msg -> eprintf "%s (ignored)\n" msg
191 ) mps;
192 (* If /etc/issue.net file exists, print up to 3 lines. *)
194 let filename = "/etc/issue.net" in
195 if g#is_file filename then (
196 printf "--- %s ---\n" filename;
197 let lines = g#head_n 3 filename in
198 Array.iter print_endline lines
199 );
200 (* Unmount everything. *)
202 g#umount_all ()
203 ) roots
204
206 guestfs(3), guestfs-examples(3), guestfs-python(3), guestfs-ruby(3),
207 <http://libguestfs.org/>, <http://caml.inria.fr/>.
208
210 Richard W.M. Jones ("rjones at redhat dot com")
211
213 Copyright (C) 2010 Red Hat Inc. <http://libguestfs.org/>
214 The examples in this manual page may be freely copied, modified and
216 distributed without any restrictions.
217 This library is free software; you can redistribute it and/or modify it
219 under the terms of the GNU Lesser General Public License as published
220 by the Free Software Foundation; either version 2 of the License, or
221 (at your option) any later version.
222 This library is distributed in the hope that it will be useful, but
224 WITHOUT ANY WARRANTY; without even the implied warranty of
225 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
226 Lesser General Public License for more details.
227 You should have received a copy of the GNU Lesser General Public
229 License along with this library; if not, write to the Free Software
230 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
231 02110-1301 USA
232libguestfs-1.8.15 2011-11-10 guestfs-ocaml(3)