System Administration Guide, Volume 1

Copying File Systems Between Disks

Two commands are used to copy file systems between disks:

The next section describes how to use the dd command to copy file systems between disks.

Making a Literal File System Copy

The dd command makes a literal (block-level) copy of a complete UFS file system to another file system or to a tape. By default, the dd command copies its standard input to its standard output.

Note -

Do not use the dd command with variable-length tape drives without first specifying an appropriate block size.

You can specify a device name in place of the standard input or the standard output or both. In this example, contents of the diskette are copied to a file in the /tmp directory:

$ dd < /floppy/floppy0 > /tmp/output.file
2400+0 records in
2400+0 records out

The dd command reports on the number of blocks it reads and writes. The number after the + is a count of the partial blocks that were copied. The default block size is 512 bytes.

The dd command syntax is different from most other commands. Options are specified as keyword=value pairs, where keyword is the option you want to set and value is the argument for that option. For example, you can replace the standard input and output with this syntax:

$ dd if=input-file of=output-file

To use the keyword=value pairs instead of the redirect symbols in the previous example, you would type:

$ dd if=/floppy/floppy0 of=/tmp/output.file

How to Clone a Disk (dd)

  1. Make sure the source and destination disks have the same disk geometry.

  2. Become superuser.

  3. Create the /reconfigure file on the system so the system will recognize the clone disk to be added when it reboots.

    # touch /reconfigure
  4. Shut down the system.

    # init 0
  5. Attach the clone disk to the system.

  6. Boot the system.

    ok boot
  7. Use the dd command to copy the master disk to the clone disk.

    # dd if=/dev/rdsk/device-name of=/dev/rdsk/device-name bs=blocksize


    Represents the overlap slice of the master disk device, usually slice 2. 


    Represents the overlap slice of the clone disk device, usually slice 2. 


    Block size, such as 128 Kbytes or 256 Kbytes. A large block size value decreases the time it takes to copy. 

  8. Check the new file system.

    # fsck /dev/rdsk/device-name
  9. Mount the clone disk's root (/) file system.

    # mount /dev/dsk/device-name /mnt
  10. Edit the clone disk's /etc/vfstab to reference the correct device names.

    For example, changing all instances of c0t3d0 with c0t1d0.

  11. Unmount the clone disk's root (/) file system.

    # umount /mnt
  12. Shut down the system.

    # init 0
  13. Boot from the clone disk to single-user mode.

    # boot diskn -s

    Note -

    The installboot command is not needed for the clone disk because the boot blocks are copied as part of the overlap slice.

  14. Unconfigure the clone disk.

    # sys-unconfig

    The system is shut down after it is unconfigured.

  15. Boot from the clone disk again and provide its system information, such as host name, time zone, and so forth.

    # boot diskn
  16. Log in as superuser to verify the system information after the system is booted.

    hostname console login:

Example--Cloning a Disk (dd)

# init 0
ok boot
# dd if=/dev/rdsk/c0t0d0s2 of=/dev/rdsk/c0t2d0s2 bs=128k
# fsck /dev/rdsk/c0t2d0s2
# mount /dev/dsk/c0t2d0s2 /mnt 
# cd /mnt/etc
# vi vfstab
(Modify entries for the new disk)
# cd /
# umount /mnt
# init 0
# boot disk2 -s
# sys-unconfig
# boot disk2