Backups Under SGI

• Other Backup Utilities
• Making Bootable Tapes
• Changes in IRIX 6.2
• Tips and Quirks

Other Backup Utilities

SGI provides as a couple additional options for performing backups; bru, Backup, and Restore. These three are very much interconnected as Backup and Restore are simply front end interfaces to bru.

bru supports a large number of options including:

• The ability to locate and back up files based on modification date.
• Multiple levels of verbosity while running.
• The ability to save and restore directories, symbolic links, block special files, and character special files.
• The ability to compare archives with the current directory hierarchy.
• The ability to ensure data integrity via a checksum computation on every archive block.

The default parameter that bru uses, such as archive device name and size, are dependent on the system. If no tape device is specified, bru uses the default /dev/tape.

bru can be called from the command line using the following syntax:

bru -options device

bru also be accessed through the Backup and Restore interfaces available under the System menu. This menu offers a Backup & Restore option. If this option is selected a Backup & Restore window appears on the screen. After "Tape drive:" a button will be displayed for each tape drive connected to the system as well as a button labeled "Remote". If the "Remote" button is selected, a field appears where the name of the system can be entered. After selecting a tape drive, an operation, either "Backup" or "Restore", must be selected.

Clicking in the "Accept" button at the bottom of the window will bring up new window where the particular files and directories may be selected for backup or restoration.

Making Bootable Tapes

In order to restore the root filesystem from tape, a special bootable stand-alone shell (SASH) tape must be created. This is also known as a miniroot tape.

1. Put in the IRIX distribution CD.
2. Enter:

   distcp /CDROM/dist/sa name_of_tape_device

3. Use the Backup utility to make a full backup of the root filesystem.

Restoring the system when the root filesystem has been damaged requires two tapes; the SASH tape and a full system backup tape.

1. Power on the system and press the Esc key to interrupt the boot sequence when the following prompt appears:

   Starting up the system....
   
   To perform system maintenance instead, press Esc key

2. When the System Maintenance Menu appears click on Recover the System.
3. Insert the bootable SASH tape when the following prompt appears:

   Insert the installation tape, then press Enter 

4. A few messages may appear on the screen while the miniroot is loading, including the following message:

   Copying installation program to disk....

5. Next this message will appear:

   CRASH RECOVERY
   
   You may type sh to get a shell prompt at most questions.
   
   Remote or local restore: ([r]emote, [l]ocal): [l]
   

   Make the appropriate selection for the tape drive being used.

6. Insert the backup tape when prompted.
7. Reboot the system when the process is complete.

Changes in IRIX 6.2

Under IRIX 6.2, dump and restore are applicable only to the EFS filesystem. When the XFS filesystem is used, xfsdump and xfsrestore must be used instead. xfsdump and xfsrestore allow data to be backed up or restored on local and remote systems. They can be used for entire filesystems, directories, or individual files.

A dump or restore can be interrupted and then resumed at any time. They can also be divided among several drives. All IRIX file types are supported: regular files, directories, symbolic links, block and character device files, hard links, and sockets.

Both commands can be used with a pipe to copy data across filesystems or the network. The syntax is:

xfsdump -s /people/ichabod - /usr | xfsrestore - /tmp

This creates an exact copy of /usr/people/ichabod in the /tmp directory. The -s option specifies a subtree of a main directory, relative to the root directory. To copy this same directory on a network host named headless:

xfsdump -s /people/ichabod - /usr | rsh headless xfsrestore - /tmp

xfsdump

xfsdump allows backups to be performed on on XFS filesystems that are mounted and in-use.Multiple dumps can be placed on the same backup media. To see a summary of the xfsdump syntax and options enter:

xfsdump -h

Basically the syntax is as follows:

xfsdump -f destination -l level -L session_label -M media_label file_to_back_up

There are several options to xfsdump, but the following are worth noting.

• destination-This is the media on which to create the backup.
• level-The dump level. If no level is lists, the default is level 0.
• session_label-If multiple dumps are placed on the same media, the session label is used to distinguish one dump from the others.
• media_label-This dictates what the dump will be labeled on the media.

By default, xfsdump keeps a record of all dumps in /var/xfsdump/inventory. The dump inventory can be viewed using the following command:

xfsdump -I

xfsrestore

To see a list of xfsrestore options enter:

xfsrestore -h

The basic syntax for xfsrestore is as follows:

xfsrestore -f source destination

As with xfsdump, there are many options to xfsrestore, including:

• -e-Tells xfsrestore not to overwrite existing files.
• -i-Interactive mode. This is used to browse an archive and select individual files for restoring.
• -L-Allows files to be located by the session label.

Note:IRIX 6.2 does not support bootable tapes.

Tips and Quirks

The IRIX version of mt supports the unload subcommand, which takes the tape drive offline and ejects the tape.

IRIX supports remote backups and restores under tar and cpio as well as bru.

Tape device files under IRIX adhere to following naming convention:

 Rewinding              Non-rewinding
------------           ---------------
/dev/rmt/tps0d3        /dev/rmt/tps0d3nr
  /dev/tape              /dev/nrtape

The default devices, /dev/tape and /dev/nrtape are linked to the first actual device, i.e. /dev/tape is linked to /dev/rmt/tps0d3. Doing an ls -l on /dev will reveal which actual devices the defaults are linked to.

crw-rw-rw- 2 root sys 144 33 April 12 1996 rmt/tps0d3
crw-rw-rw- 2 root sys 144 35 April 12 1996 rmt/tps0d3nr
crw-rw-rw- 2 root sys 144 42 April 12 1996 rmt/tps0d4
crw-rw-rw- 2 root sys 144 42 April 12 1996 rmt/tps0d4nr
crw-rw-rw- 2 root sys 144 33 April 12 1996 tape
crw-rw-rw- 2 root sys 144 35 April 12 1996 nrtape

So here tape and nrtape correspond to the rewinding and non-rewinding modes of device tps0d3. To change the devices that tape and nrtape are linked to use:

rm -f /dev/tape /dev/nrtape
ln /dev/rmt/tps0d4 /dev/tape
ln /dev/rmt/tps0d4nr /dev/nrtape

This will link tape and nrtape to rmt/tps0d4.

By default, SGIs use variable block sizes when backups are created. This can make it difficult to read a tape created on an SGI on any other system. Backups can be created using fixed block size, but this must be specified.