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VOL(1)                      General Commands Manual                     VOL(1)

       vol - split input on or combine output from several volumes

       vol [-rw1] [-b blocksize] [-m multiple] [size] device

       Vol  either  reads  a  large  input  stream  from  standard  input  and
       distributes it over several volumes or combines volumes and sends  them
       to   standard   output.    The   size  of  the  volumes  is  determined
       automatically if the device supports this, but may be specified  before
       the  argument  naming the device if automated detection is not possible
       or if only part of the physical volume is used.  The direction  of  the
       data  is  automatically  determined  by  checking  whether the input or
       output of vol is a file or pipe.  Use the -r or -w flag if you want  to
       specify the direction explicitly, in shell scripts for instance.

       Vol  waits  for  each new volume to be inserted, typing return makes it
       continue.  If no size is explicitely given then the size of the  device
       is determined each time before it is read or written, so it is possible
       to mix floppies of different sizes.  If the size cannot  be  determined
       (probably a tape) then the device is assumed to be infinitely big.  Vol
       can be used both for block or character devices.  It  will  buffer  the
       data and use a block size appropriate for fixed or variable block sized

       Vol reads or writes 8192 bytes  to  block  devices,  usually  floppies.
       Character  devices  are  read or written using a multiple of 512 bytes.
       This multiple has an upper limit of 32767 bytes (16-bit machine), 64 kb
       (32-bit),  or  even  1  Mb  (32-bit  VM).   The last partial write to a
       character device is  padded  with  zeros  to  the  block  size.   If  a
       character  device  is a tape device that responds to the mtio(4) status
       call then the reported tape block size will be  used  as  the  smallest
       unit.  If the tape is a variable block length device then it is read or
       written like a block device, 8192 bytes at the  time,  with  a  minimum
       unit of one byte.

       All  sizes  may be suffixed by the letters M, k, b or w to multiply the
       number by mega, kilo, block (512), or word (2).   The  volume  size  by
       default in kilobytes if there is no suffix.

       -rw    Explicitly  specify  reading  or  writing.   Almost mandatory in

       -1     Just one volume, start immediately.

       -b blocksize
              Specify the device block size.

       -m multiple
              Specify the maximum read or write size of multiple blocks.   The
              -b and -m options allow one to modify the block size assumptions
              that are made above.  These assumptions are -b  1  -m  8192  for
              block  devices or variable length tapes, and -b 512 -m 65536 for
              character devices (32 bit  machine.)   These  options  will  not
              override  the  tape  block  size found out with an mtio(4) call.
              The multiple may be larger then the default if vol can  allocate
              the memory required.

       To back up a tree to floppies as a compressed tarfile:

              tar cf - . | compress | vol /dev/fd0

       To restore a tree from 720 kb images from possibly bigger floppies:

              vol 720 /dev/fd0 | uncompress | tar xfp -

       Read or write a device with 1024 byte blocks:

              vol -b 1k /dev/rsd15

       Read  or write a variable block length tape using blocking factor 20 as
       used by default by many tar(1) commands:

              vol -m 20b /dev/rst5

       Note that -m was used in the last example.  It sets the size to use  to
       read  or  write,  -b  sets  the basic block size that may be written in

       dd(1), tar(1), mt(1), mtio(4).