Image Backup

An image backup is one that copies an entire disk, not selected files or directory trees, to another device. If the backup is performed on a system disk, the necessary boot records are copied as well. This is also called a full backup. If the destination is a tape, everything on disk is written to a container file on tape. This container file is termed a save set. The commands for this operation are as follows:

     $ BACKUP/IMAGE/VERIFY/RECORD/IGNORE=INTERLOCK -     _$ DUA0: -     _$ MUA400:FULLBU.SAV/REWIND/LABEL=FULL 

Reading the BACKUP command line from left to right, it specifies that an image backup is to be created.

• The /IMAGE qualifier signifies the option.

• The / VERIFY qualifier specifies that after the tape is written, all files in the save set are to be read back and compared to the original on disk.

• The /RECORD qualifier causes BACKUP to add the date and time of the backup operation to each file on disk. This provides an audit trail for the manager and is used for incremental backups, as described later. The date is accessed as shown:

     $ dir/date=backup login.com;0   Directory FACULTY:[DMILLER]   LOGIN.COM;101        24-AUG-2002 07:51:35.60 

• If the disk is mounted so that anyone may access it, open files will not be backed up. To avoid this treatment, add the / IGNORE=INTERLOCK qualifier.

• The source is a disk on device DUA0:.

• The destination is a tape on device MUA400:.

• The save set is to be named FULLBU.SAV.

• The /REWIND qualifier ensures that the tape will be initialized before backup.

• The /LABEL qualifier specifies the logical label assigned to the tape and is limited to six characters.

If the tape is too small to contain all of the files on the disk, the operator will be instructed to supply a new tape. When he or she responds to the prompt, the backup operation continues. The dialog is similar to the following:

     %BACKUP-I-RESUME, resuming operation on volume 2     %BACKUP-I-READYWRITE, mount volume FULL on MUA400: for writing     Respond with YES when ready: 

Alternately, tape robots can be connected to the tape drive to switch tapes automatically.

If the destination is another disk, there is another option. The destination disk can contain either a save set or a directory tree. This latter option is termed a disk-to-disk copy. The command is illustrated as follows. The destination disk, DUA300:, has to be private, not public, because it will be completely reinitialized and it should be large enough to contain all of the files on DUA0:. This is not a bit-by-bit copy, and DUA300: will be a defragmented version of DUA0:.

If defragmentation is the goal, Disk File Optimizer (DFO), Compaq/HP's defragmention program, will run on an active disk to defragment both files and free space.

    $ BACKUP/IMAGE/VERIFY/RECORD/IGNORE=INTERLOCK -     _$ DUA0: -     _$ DUA300: 

Thus, DUA300: becomes an exact duplicate of DUA0:. If DUA0: is bootable, DUA300: will be as well.