ocaml: Translate C examples into OCaml and include documentation.

[libguestfs.git] / ocaml / examples / create_disk.ml

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+(* Example showing how to create a disk image. *)
+
+open Unix
+open Printf
+
+let output = "disk.img"
+
+let () =
+  let g = new Guestfs.guestfs () in
+
+  (* Create a raw-format sparse disk image, 512 MB in size. *)
+  let fd = openfile output [O_WRONLY;O_CREAT;O_TRUNC;O_NOCTTY] 0o666 in
+  ftruncate fd (512 * 1024 * 1024);
+  close fd;
+
+  (* Set the trace flag so that we can see each libguestfs call. *)
+  g#set_trace true;
+
+  (* Set the autosync flag so that the disk will be synchronized
+   * automatically when the libguestfs handle is closed.
+   *)
+  g#set_autosync true;
+
+  (* Attach the disk image to libguestfs. *)
+  g#add_drive_opts ~format:"raw" ~readonly:false output;
+
+  (* 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.
+   *)
+  let devices = g#list_devices () in
+  if Array.length devices <> 1 then
+    failwith "error: expected a single device from list-devices";
+
+  (* Partition the disk as one single MBR partition. *)
+  g#part_disk devices.(0) "mbr";
+
+  (* Get the list of partitions.  We expect a single element, which
+   * is the partition we have just created.
+   *)
+  let partitions = g#list_partitions () in
+  if Array.length partitions <> 1 then
+    failwith "error: expected a single partition from list-partitions";
+
+  (* Create a filesystem on the partition. *)
+  g#mkfs "ext4" partitions.(0);
+
+  (* Now mount the filesystem so that we can add files. *)
+  g#mount_options "" partitions.(0) "/";
+
+  (* Create some files and directories. *)
+  g#touch "/empty";
+  let message = "Hello, world\n" in
+  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 'autosync' was set (above) we can just close the handle
+   * and the disk contents will be synchronized.  You can also do
+   * this manually by calling g#umount_all and g#sync.
+   *
+   * 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 ()