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 noticeable 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 (* Attach the disk image to libguestfs. *)
86 g#add_drive_opts ~format:"raw" ~readonly:false output;
87 (* Run the libguestfs back-end. *)
89 g#launch ();
90 (* Get the list of devices. Because we only added one drive
92 * above, we expect that this list should contain a single
93 * element.
94 *)
95 let devices = g#list_devices () in
96 if Array.length devices <> 1 then
97 failwith "error: expected a single device from list-devices";
98 (* Partition the disk as one single MBR partition. *)
100 g#part_disk devices.(0) "mbr";
101 (* Get the list of partitions. We expect a single element, which
103 * is the partition we have just created.
104 *)
105 let partitions = g#list_partitions () in
106 if Array.length partitions <> 1 then
107 failwith "error: expected a single partition from list-partitions";
108 (* Create a filesystem on the partition. *)
110 g#mkfs "ext4" partitions.(0);
111 (* Now mount the filesystem so that we can add files. *)
113 g#mount partitions.(0) "/";
114 (* Create some files and directories. *)
116 g#touch "/empty";
117 let message = "Hello, world\n" in
118 g#write "/hello" message;
119 g#mkdir "/foo";
120 (* This one uploads the local file /etc/resolv.conf into
122 * the disk image.
123 *)
124 g#upload "/etc/resolv.conf" "/foo/resolv.conf";
125 (* Because we wrote to the disk and we want to detect write
127 * errors, call g#shutdown. You don't need to do this:
128 * g#close will do it implicitly.
129 *)
130 g#shutdown ();
131 (* Note also that handles are automatically closed if they are
133 * reaped by the garbage collector. You only need to call close
134 * if you want to close the handle right away.
135 *)
136 g#close ()
137
139 (* Example showing how to inspect a virtual machine disk. *)
140 open Printf
142 let disk =
144 if Array.length Sys.argv = 2 then
145 Sys.argv.(1)
146 else
147 failwith "usage: inspect_vm disk.img"
148 let () =
150 let g = new Guestfs.guestfs () in
151 (* Attach the disk image read-only to libguestfs. *)
153 g#add_drive_opts (*~format:"raw"*) ~readonly:true disk;
154 (* Run the libguestfs back-end. *)
156 g#launch ();
157 (* Ask libguestfs to inspect for operating systems. *)
159 let roots = g#inspect_os () in
160 if Array.length roots = 0 then
161 failwith "inspect_vm: no operating systems found";
162 Array.iter (
164 fun root ->
165 printf "Root device: %s\n" root;
166 (* Print basic information about the operating system. *)
168 printf " Product name: %s\n" (g#inspect_get_product_name root);
169 printf " Version: %d.%d\n"
170 (g#inspect_get_major_version root)
171 (g#inspect_get_minor_version root);
172 printf " Type: %s\n" (g#inspect_get_type root);
173 printf " Distro: %s\n" (g#inspect_get_distro root);
174 (* Mount up the disks, like guestfish -i.
176 *
177 * Sort keys by length, shortest first, so that we end up
178 * mounting the filesystems in the correct order.
179 *)
180 let mps = g#inspect_get_mountpoints root in
181 let cmp (a,_) (b,_) =
182 compare (String.length a) (String.length b) in
183 let mps = List.sort cmp mps in
184 List.iter (
185 fun (mp, dev) ->
186 try g#mount_ro dev mp
187 with Guestfs.Error msg -> eprintf "%s (ignored)\n" msg
188 ) mps;
189 (* If /etc/issue.net file exists, print up to 3 lines. *)
191 let filename = "/etc/issue.net" in
192 if g#is_file filename then (
193 printf "--- %s ---\n" filename;
194 let lines = g#head_n 3 filename in
195 Array.iter print_endline lines
196 );
197 (* Unmount everything. *)
199 g#umount_all ()
200 ) roots
201
203 guestfs(3), guestfs-examples(3), guestfs-erlang(3), guestfs-java(3),
204 guestfs-lua(3), guestfs-perl(3), guestfs-python(3), guestfs-recipes(1),
205 guestfs-ruby(3), http://libguestfs.org/, http://caml.inria.fr/.
206
208 Richard W.M. Jones ("rjones at redhat dot com")
209
211 Copyright (C) 2010-2012 Red Hat Inc.
212
214 This manual page contains examples which we hope you will use in your
215 programs. The examples may be freely copied, modified and distributed
216 for any purpose without any restrictions.
217
219 To get a list of bugs against libguestfs, use this link:
220 https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
221 To report a new bug against libguestfs, use this link:
223 https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
224 When reporting a bug, please supply:
226 · The version of libguestfs.
228 · Where you got libguestfs (eg. which Linux distro, compiled from
230 source, etc)
231 · Describe the bug accurately and give a way to reproduce it.
233 · Run libguestfs-test-tool(1) and paste the complete, unedited output
235 into the bug report.
236libguestfs-1.20.11 2013-08-27 guestfs-ocaml(3)