libguestfs/java/examples/CreateDisk.java

// 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);

            // Attach the disk image to libguestfs.
            @SuppressWarnings("serial") 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 (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 we wrote to the disk and we want to detect write
            // errors, call g.shutdown.  You don't need to do this:
            // g.close will do it implicitly.
            g.shutdown ();

            // 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);
        }
    }
}