124 lines
4.9 KiB
HTML
124 lines
4.9 KiB
HTML
<HTML>
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<HEAD>
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<TITLE>vol(1)</TITLE>
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</HEAD>
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<BODY>
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<H1>vol(1)</H1>
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<HR>
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<PRE>
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</PRE>
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<H2>NAME</H2><PRE>
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vol - split input on or combine output from several volumes
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</PRE>
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<H2>SYNOPSIS</H2><PRE>
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<STRONG>vol</STRONG> [<STRONG>-rw1</STRONG>] [<STRONG>-b</STRONG> <EM>blocksize</EM>] [<STRONG>-m</STRONG> <EM>multiple</EM>] [<EM>size</EM>] <EM>device</EM>
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</PRE>
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<H2>DESCRIPTION</H2><PRE>
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<STRONG>Vol</STRONG> either reads a large input stream from standard input and distributes
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it over several volumes or combines volumes and sends them to standard
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output. The size of the volumes is determined automatically if the
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device supports this, but may be specified before the argument naming the
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device if automated detection is not possible or if only part of the
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physical volume is used. The direction of the data is automatically
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determined by checking whether the input or output of <STRONG>vol</STRONG> is a file or
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pipe. Use the <STRONG>-r</STRONG> or <STRONG>-w</STRONG> flag if you want to specify the direction
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explicitly, in shell scripts for instance.
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<STRONG>Vol</STRONG> waits for each new volume to be inserted, typing return makes it
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continue. If no size is explicitely given then the size of the device is
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determined each time before it is read or written, so it is possible to
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mix floppies of different sizes. If the size cannot be determined
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(probably a tape) then the device is assumed to be infinitely big. <STRONG>Vol</STRONG>
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can be used both for block or character devices. It will buffer the data
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and use a block size appropriate for fixed or variable block sized tapes.
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<STRONG>Vol</STRONG> reads or writes 8192 bytes to block devices, usually floppies.
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Character devices are read or written using a multiple of 512 bytes.
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This multiple has an upper limit of 32767 bytes (16-bit machine), 64 kb
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(32-bit), or even 1 Mb (32-bit VM). The last partial write to a
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character device is padded with zeros to the block size. If a character
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device is a tape device that responds to the <STRONG><A HREF="../man4/mtio.4.html">mtio(4)</A></STRONG> status call then the
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reported tape block size will be used as the smallest unit. If the tape
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is a variable block length device then it is read or written like a block
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device, 8192 bytes at the time, with a minimum unit of one byte.
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All sizes may be suffixed by the letters <STRONG>M</STRONG>, <STRONG>k</STRONG>, <STRONG>b</STRONG> or <STRONG>w</STRONG> to multiply the
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number by mega, kilo, block (512), or word (2). The volume size by
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default in kilobytes if there is no suffix.
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</PRE>
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<H2>OPTIONS</H2><PRE>
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<STRONG>-rw</STRONG> Explicitly specify reading or writing. Almost mandatory in scripts.
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<STRONG>-1</STRONG> Just one volume, start immediately.
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<STRONG>-b</STRONG> <EM>blocksize</EM>
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Specify the device block size.
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<STRONG>-m</STRONG> <EM>multiple</EM>
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Specify the maximum read or write size of multiple blocks. The <STRONG>-b</STRONG>
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and <STRONG>-m</STRONG> options allow one to modify the block size assumptions that
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are made above. These assumptions are <STRONG>-b</STRONG> <STRONG>1</STRONG> <STRONG>-m</STRONG> <STRONG>8192</STRONG> for block
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devices or variable length tapes, and <STRONG>-b</STRONG> <STRONG>512</STRONG> <STRONG>-m</STRONG> <STRONG>65536</STRONG> for character
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devices (32 bit machine.) These options will not override the tape
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block size found out with an <STRONG><A HREF="../man4/mtio.4.html">mtio(4)</A></STRONG> call. The multiple may be
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larger then the default if <STRONG>vol</STRONG> can allocate the memory required.
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</PRE>
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<H2>EXAMPLES</H2><PRE>
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To back up a tree to floppies as a compressed tarfile:
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tar cf - . | compress | vol /dev/fd0
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To restore a tree from 720 kb images from possibly bigger floppies:
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vol 720 /dev/fd0 | uncompress | tar xfp -
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Read or write a device with 1024 byte blocks:
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vol -b 1k /dev/rsd15
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Read or write a variable block length tape using blocking factor 20 as
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used by default by many <STRONG><A HREF="../man1/tar.1.html">tar(1)</A></STRONG> commands:
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vol -m 20b /dev/rst5
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Note that <STRONG>-m</STRONG> was used in the last example. It sets the size to use to
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read or write, <STRONG>-b</STRONG> sets the basic block size that may be written in
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multiples.
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</PRE>
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<H2>SEE ALSO</H2><PRE>
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<STRONG><A HREF="../man1/dd.1.html">dd(1)</A></STRONG>, <STRONG><A HREF="../man1/tar.1.html">tar(1)</A></STRONG>, <STRONG><A HREF="../man1/mt.1.html">mt(1)</A></STRONG>, <STRONG><A HREF="../man4/mtio.4.html">mtio(4)</A></STRONG>.
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</PRE>
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</BODY>
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</HTML>
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