XBACKUP(ADM) UNIX System V
Name
xbackup - performs XENIX incremental filesystem backup
Syntax
xbackup [ key [ arguments ] filesystem ]
Description
xbackup copies all files changed after a certain date in the
date in the filesystem. xbackup is used for XENIX
filesystems; use backup(ADM) for UNIX filesystems. 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 xbackup on the next argument file 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 file system
and each xbackup level.
0-9 This number is the ``xbackup level''. Backs up all
files modified since the last date stored in the file
/etc/ddate for the same file system at lesser levels.
If no date is determined by the level, the beginning of
time is assumed; thus the option 0 causes the entire
file system 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 This option is used when backing up to a block-
structured device, such as a floppy disk. The size (in
K-bytes) 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 file system 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 file system and the xbackup device depend on the
settings of the variables DISK and TAPE, respectively, in
the file /etc/default/backup.
Files
/etc/ddate Records xbackup dates of file
system/level
/etc/default/backup Default xbackup information
See Also
cpio(C), default(F), xdumpdir(ADM), xrestore(ADM),
restore(ADM), sddate(C), backup(ADM), xbackup(F), System
Administrator's Guide
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.
Notes
Sizes are based on 1600 BPI for blocked tape; the raw
magnetic tape device has to be used to approach these
densities. Write errors to the xbackup device are usually
fatal. Read errors on the file system are ignored.
If the default archive medium specified in
/etc/default/xbackup or /etc/default/restor is block
structured, (i.e. floppy disk) then the volume size in
Kbytes 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 file system.
When backing up to floppy disks, be sure to have enough
formatted floppies ready before starting a 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.
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(ADM) 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 20 megabyte filesystem that is only 50 percent full,
you still won't be able to restore the backup volumes onto a
15 megabyte filesystem. The reinstallation chapter explains
that you must use cpio(C)-based utilities (such as the
sysadmsh Backups->Create selection) to back up your system.
Value Added
xbackup is an extension of AT&T System V provided by the
Santa Cruz Operation.
(printed 2/15/90) XBACKUP(ADM)