NAME¶
guestfs-java - How to use libguestfs from Java
SYNOPSIS¶
import com.redhat.et.libguestfs.*;
GuestFS g = new GuestFS ();
g.add_drive_opts ("disk.img", null);
g.launch ();
DESCRIPTION¶
This manual page documents how to call libguestfs from the Java 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
guestfs(3).
CLOSING THE HANDLE¶
The handle is closed when it is reaped by the garbage collector. Because
libguestfs handles include a lot of state, it is also possible to close (and
hence free) them explicitly by calling the "close" method.
EXCEPTIONS¶
Errors from libguestfs functions are mapped into the
"LibGuestFSException" exception. This has a single parameter which
is the error message (a "String").
Calling any method on a closed handle raises the same exception.
EXAMPLE 1: CREATE A DISK IMAGE¶
// Example showing how to create a disk image.
import java.io.*;
import java.util.Map;
import java.util.HashMap;
import com.redhat.et.libguestfs.*;
public class CreateDisk
{
static String output = "disk.img";
public static void main (String[] argv)
{
try {
GuestFS g = new GuestFS ();
// Create a raw-format sparse disk image, 512 MB in size.
RandomAccessFile f = new RandomAccessFile (output, "rw");
f.setLength (512 * 1024 * 1024);
f.close ();
// 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.
Map<String, Object> optargs = new HashMap<String, Object>() {
{
put ("format", "raw");
put ("readonly", Boolean.FALSE);
}
};
g.add_drive_opts (output, optargs);
// 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.
String[] devices = g.list_devices ();
if (devices.length != 1)
throw new 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.
String[] partitions = g.list_partitions ();
if (partitions.length != 1)
throw new 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");
String message = "Hello, world\n";
g.write ("/hello", message.getBytes());
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 ();
}
catch (Exception exn) {
System.err.println (exn);
System.exit (1);
}
}
}
EXAMPLE 2: INSPECT A VIRTUAL MACHINE DISK IMAGE¶
// Example showing how to inspect a virtual machine disk.
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import com.redhat.et.libguestfs.*;
public class InspectVM
{
static final Comparator<String> COMPARE_KEYS_LEN =
new Comparator<String>() {
public int compare (String k1, String k2) {
return k1.length() - k2.length();
}
};
public static void main (String[] argv)
{
try {
if (argv.length != 1)
throw new Error ("usage: InspectVM disk.img");
String disk = argv[0];
GuestFS g = new GuestFS ();
// Attach the disk image read-only to libguestfs.
Map<String, Object> optargs = new HashMap<String, Object>() {
{
//put ("format", "raw");
put ("readonly", Boolean.TRUE);
}
};
g.add_drive_opts (disk, optargs);
// Run the libguestfs back-end.
g.launch ();
// Ask libguestfs to inspect for operating systems.
String roots[] = g.inspect_os ();
if (roots.length == 0)
throw new Error ("inspect_vm: no operating systems found");
for (String root : roots) {
System.out.println ("Root device: " + root);
// Print basic information about the operating system.
System.out.println (" Product name: " +
g.inspect_get_product_name (root));
System.out.println (" Version: " +
g.inspect_get_major_version (root) +
"." +
g.inspect_get_minor_version (root));
System.out.println (" Type: " +
g.inspect_get_type (root));
System.out.println (" 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.
Map<String,String> mps = g.inspect_get_mountpoints (root);
List<String> mps_keys = new ArrayList (mps.keySet ());
Collections.sort (mps_keys, COMPARE_KEYS_LEN);
for (String mp : mps_keys) {
String dev = mps.get (mp);
try {
g.mount_ro (dev, mp);
}
catch (Exception exn) {
System.err.println (exn + " (ignored)");
}
}
// If /etc/issue.net file exists, print up to 3 lines.
String filename = "/etc/issue.net";
if (g.is_file (filename)) {
System.out.println ("--- " + filename + " ---");
String[] lines = g.head_n (3, filename);
for (String line : lines)
System.out.println (line);
}
// Unmount everything.
g.umount_all ();
}
}
catch (Exception exn) {
System.err.println (exn);
System.exit (1);
}
}
}
SEE ALSO¶
guestfs(3),
guestfs-examples(3),
guestfs-erlang(3),
guestfs-ocaml(3),
guestfs-perl(3),
guestfs-python(3),
guestfs-recipes(1),
guestfs-ruby(3),
<
http://libguestfs.org/>, <
http://caml.inria.fr/>.
AUTHORS¶
Richard W.M. Jones ("rjones at redhat dot com")
COPYRIGHT¶
Copyright (C) 2011 Red Hat Inc. <
http://libguestfs.org/>
The examples in this manual page may be freely copied, modified and distributed
without any restrictions.
This library is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your option) any
later version.
This library is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
details.
You should have received a copy of the GNU Lesser General Public License along
with this library; if not, write to the Free Software Foundation, Inc., 51
Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
