BACKUP(C) XENIX System V BACKUP(C)
Name
backup - Performs incremental file system backup.
Syntax
backup [ key [ arguments ] filesystem ]
Description
backup copies all files changed after a certain date in the
date in the filesystem. The key specifies the date and
other options about the backup, where a key consists of
characters from the set 0123456789kfusd. The meanings of
these characters are described below:
f Places the backup on the next argument file instead of
the default device.
u If the backup completes successfully, writes the date
of the beginning of the backup to the file /etc/ddate.
This file records a separate date for each file system
and each backup level.
0-9 This number is the ``backup 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 backups 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,
backup will wait for reels to be changed. The default
size is 2,300 feet.
d For backups 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
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BACKUP(C) XENIX System V BACKUP(C)
default file system is backed up to the default device.
The first backup should be a full level-0 backup:
backup 0u
Next, periodic level 9 backups should be made on an
exponential progression of tapes or floppies:
backup 9u
This progression is shown as follows:
1 2 1 3 1 2 1 4 ...
where backup 1 is used every other time, backup 2 every
fourth, backup 3 every eighth, etc.) When the level-9
incremental backup becomes unmanageable because a tape is
full or too many floppies are required, a level-1 backup
should be made:
backup 1u
After this, the exponential series should progress as if
uninterrupted. These level-9 backups are based on the
level-1 backup, which is based on the level-0 full backup.
This progression of levels of backups can be carried as far
as desired.
The default file system and the backup device depend on the
settings of the variables DISK and TAPE, respectively, in
the file /etc/default/backup.
Files
/etc/ddate Records backup dates of file
system/level
etc/default/backup Default backup information
See Also
XENIX Operations Guide
cpio(C), default(M), dumpdir(C), restore(C), sddate(C),
backup(F)
Diagnostics
If the backup 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.
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BACKUP(C) XENIX System V BACKUP(C)
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 backup device are usually
fatal. Read errors on the file system are ignored.
It is not possible to successfully restore an entire active
root file system.
Warning
When backing up to floppy disks, be sure to have enough
formatted floppies ready before starting a backup.
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