MULTIVOL(1) RISC/os Reference Manual MULTIVOL(1)
NAME
multivol - handle multivolume files
SYNOPSIS
multivol -o [-vtw] [-b blocksize] [-n count] [-l label]
[device]
multivol -i [-vtw] [-b blocksize] [-n count] [-l label]
[device]
multivol -t [device]
DESCRIPTION
multivol allows for the convenient use of multiple volume
files such as when backing up output from cpio/tar over
several floppy disks.
Option -o reads the standard input file, breaking it into
volumes on the output device. Option -i reads volumes from
the device, concatenates them and writes the result to stan-
dard output.
The device to use is given by the device argument, or
/dev/multivol if none is specified. Normally this will be a
character special file corresponding to a raw disk or tape
unit. It does not have to be a random access device: mul-
tivol only accesses it sequentially. However, multivol may
close and re-open a volume in order to rewind devices such
as magnetic tape. Note that this device may not exist on
your system. If you create a default device, you may wish
to set up an entry in the MKDEV(1M) device database to keep
the information available in case the device directory needs
to be rebuilt.
The -b blocksize argument specifies the physical block size
to be used. This number may end with k or b to specify mul-
tiplication by 1024 or 512 respectively. With a floppy disk
it can usefully be made the size of one track. The default
physical block size is 512 bytes. If the device or its
driver does not allow successful writing all the way to the
end of a physical volume, such as with magnetic tape, the -n
count options should be used to specify the maximum number
of physical blocks to be written on one volume.
The -l label option allows the user to supply a short string
to be written onto the volume for identification.
Before reading or writing a new volume, multivol prompts on
the controlling terminal for the user to insert the
appropriate volume into the physical device and waits for a
new-line to be typed. With -i, if the volume inserted is
not a multivol volume, is not the next volume in sequence,
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or does not have the same date stamp as the previous volume,
multivol verifies that you really want to read it.
multivol writes an ASCII header on each volume, and checksum
info in each block hence the actual amount of data stored on
each volume will be slightly less than its physical size.
The -t option prints some of this header information on
standard error. It includes:
⊕ the date that the volume was written
⊕ the sequence number of the volume
⊕ any label string supplied at the time the volume was
written
If you specify -w with -i or -o multivol assumes the -t
option, and asks you to verify that each volume really is
the required one.
The -v option tells multivol to write various other verbose
information on standard error such as an indication of how
many blocks it has read or written.
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Tape Volume Capacities
The table below shows the capacities of 150, 450, and 600-
foot tapes on the QIC-11, QIC-24, QIC-120, and QIC-150 tape
drives respectively.
Tape Length
150' 450' 600'
QIC-11 30000** 90000** 120000**
QIC-24 28000** 88000** 116000**
QIC-120 65918 N/A* 263672**
QIC-150 79101 N/A* 316406**
**512-byte blocks
*QIC-120 and QIC-150 cannot write 450' tapes.
If you wish to convert the 512-byte capacities to megabytes
(where 1024 bytes = 1 MB), divide by 200 (or divide by 2 and
drop the last two 0's) for a rough approximation. For exam-
ple, 30000 512-byte blocks equals approximately 150 MB.
The following table lists the size (in megabytes) and the
length of tapes for the Exabyte EXB-8200 8mm cartridge tape
drive. There are two types of cartridges, P5 and P6, and
you should look at the cartridge to determine the type you
are using.
Length (feet)
Cartridge Size P6 P5
256MB 48 69
512MB 98 128
1024MB 176 246
1536MB 261 366
2048MB 346 n/a
EXAMPLES
Tell me what you know about this volume:
multivol -t
Backup a directory to the default device:
tar cf - mydir | multivol -o
and retrieve it again:
cd mydir
multivol -i | tar xf -
Backup to tape all files changed since last time:
touch /etc/multivoldate1
find / -newer /etc/multivoldate2 -print | cpio -ov |
multivol -o -l WEEKLY -b 20k -n 1000 /dev/rmt0
mv /etc/multivoldate1 /etc/multivoldate2
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Retrieve a file from that backup:
cd /
multivol -i /dev/rmt0 | cpio -idmv usr/myname/myfile
FILES
/dev/tty where prompts are written and responses read
/dev/multivol the default device (NOTE: may not be set up)
SEE ALSO
tar(1), cpio(1), MKDEV(1M)
DIAGNOSTICS
A message is written on standard error and multivol ter-
minates in the event of
⊕ incorrect usage
⊕ not being able to open the device
⊕ not being able to open /dev/tty
⊕ a device I/O error
ERRORS
In the event of an I/O error you may have to start again
with the first volume depending on the nature of the file
and the program which produced it. In many cases it simply
means the end of the volume has been reached, and no more
can be read/written. If a block limit has been set multivol
will indicate this condition.
When reading or writing, multivol attempts to read the
volumes header to display what is being written over, or to
determine the block size recorded in the header. Some raw
devices will return an I/O error when the volume has not
been written before, or has been previously written with a
different block size. Hence the volume header cannot be
read until the original block size is also specified. The
first time a volume is written, multivol may signal an I/O
error as it attempts to read the header, but will proceed to
allow the volume to be written.
Volume labels may not contain white space and are limited to
14 characters.
Some tape device drivers cannot handle a read/write request
while the tape is rewinding, for such drivers the -w switch
is recommended in place of just -t
When using commands such as cpio(1) or tar(1), do not use
any of the blocking factor options of those commands.
Instead, specify the blocking factor to multivol for the
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device.
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