xbackup(ADM)

xbackup -- perform XENIX incremental filesystem backup

Syntax

xbackup [ key [ arguments ] filesystem ]

Description

xbackup copies all files changed after a certain date in the filesystem. xbackup is used for XENIX filesystems; use backup(ADM) for UNIX filesystems. (xdump is a link to xbackup, retained for historical reasons.) The key specifies the date and other options about the xbackup, where a key consists of characters from the set: 0123456789kfusd. The meanings of these characters are described below:

f: Places the backup on the file specified by the next argument instead of the default device.
u: If the xbackup completes successfully, writes the date of the beginning of the xbackup to the file /etc/ddate. This file records a separate date for each filesystem and each xbackup level.
09: This number is the xbackup level. Backs up all files modified since the last date stored in the file /etc/ddate for the same filesystem at lesser levels. If no date is determined by the level, the beginning of time is assumed; thus the option 0 causes the entire filesystem to be backed up.
s: For xbackups to magnetic tape, the size of the tape is specified in feet. The number of feet is taken from the next argument. When the specified size is reached, xbackup will wait for reels to be changed. The default size is 2,300 feet.
d: For xbackups to magnetic tape, the density of the tape, expressed in BPI is taken from the next argument. This is used in calculating the amount of tape used per write. The default is 1600.
k: The size (in Kilobytes) of the volume being written is taken from the next argument. If the k argument is specified, any s and d arguments are ignored. The default is to use s and d.

If no arguments are given, the key is assumed to be 9u and a default filesystem is backed up to the default device.

The first xbackup should be a full level-0 xbackup:

xbackup 0u

Next, periodic level 9 xbackups should be made on an exponential progression of tapes or floppies:

xbackup 9u

This progression is shown as follows:

1 2 1 3 1 2 1 4 ...

where xbackup 1 is used every other time, xbackup 2 every fourth, xbackup 3 every eighth, etc.) When the level-9 incremental xbackup becomes unmanageable because a tape is full or too many floppies are required, a level-1 xbackup should be made:

xbackup 1u

After this, the exponential series should progress as if uninterrupted. These level-9 xbackups are based on the level-1 xbackup, which is based on the level-0 full xbackup. This progression of levels of xbackups can be carried as far as desired.

The default filesystem and the xbackup device depend on the settings of the variables DISK and TAPE respectively, in the file /etc/default/backup.

Diagnostics

If the xbackup requires more than one volume (where a volume is likely to be a floppy disk or tape), you will be asked to change volumes. Press <Return> after changing volumes.

Warning

If you have a XENIX filesystem, or have been administering one, it is important to realize that you cannot use backups created by the xbackup utility. These backups do not allow downsizing when you restore. This is true even if the backed-up filesystem is not full. For example, if you back up a 20MB filesystem that is only 50 percent full, you still won't be able to restore the backup volumes onto a 15MB filesystem. The reinstallation chapter explains that you must use cpio(C)-based utilities (such as the Backup Manager) to back up your system.

Limitations

Sizes are based on 1600 BPI for blocked tape. Although the s and d options are used by default, they are not commonly used; the k option is more popular because it specifies size in Kilobytes. Write errors to the backup device are usually fatal. Read errors on the filesystem are ignored.

If the default archive medium specified in /etc/default/xbackup or /etc/default/restor is block structured, (that is, floppy disk) then the volume size in Kilobytes must be specified on the command line. Neither utility works correctly without this information. For example, using the default device (below) with the xbackup command, enter the following:

xbackup k 360

The default device entry for /etc/default/xbackup (tape=/dev/xxx) and /etc/default/restor (archive=/dev/xxx) is /dev/rfd02.

It is not possible to successfully restore an entire active root filesystem.

When backing up to floppy disks, be sure to have enough formatted floppies ready before starting an xbackup. You must also be sure to close the floppy door when inserting floppy disks. If you fail to do so in a multi-floppy xbackup, the entire xbackup will fail and you will have to begin again.

You should never xbackup more than one filesystem to the tape devices /dev/nrct0 and /dev/nrct2. This is because, although xbackup can write more than one filesystem to /dev/nrct0 or /dev/nrct2, restore may not be able to restore more than one filesystem from these devices.

Files

/etc/ddate: records xbackup dates of filesystem/level
/etc/default/backup: default xbackup information

Standards conformance

xbackup is not part of any currently supported standard; it is an extension of AT&T System V provided by The Santa Cruz Operation, Inc.