VOL.1
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- VOL(1) Minix Programmer's Manual VOL(1)
- NAME
- vol - split input on or combine output from several volumes
- SYNOPSIS
- vol [-rw1] [-b blocksize] [-m multiple] [size] device
- DESCRIPTION
- 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 tapes.
- 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.
- OPTIONS
- -rw Explicitly specify reading or writing. Almost mandatory in scripts.
- -1 Just one volume, start immediately.
- -b blocksize
- Specify the device block size.
- 1
-
- VOL(1) Minix Programmer's Manual VOL(1)
- -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.
- EXAMPLES
- 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
- multiples.
- SEE ALSO
- dd(1), tar(1), mt(1), mtio(4).
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