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.TH DISKSIM 8
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.SH NAME
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disksim \- disk simulator
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.SH SYNOPSIS
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.B aux/disksim
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[
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.B -r
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]
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[
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.B -f
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.I file
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]
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[
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.B -s
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.I srvname
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]
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[
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.B -m
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.I mtpt
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]
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[
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.I diskname
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]
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.SH DESCRIPTION
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.I Disksim
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presents an in-memory disk in the manner of the
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.IR sd (3)
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device on
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.IB mtpt / diskname
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(default
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.BR /dev/sdXX ).
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The disk is initialized to zeros;
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non-zeroed blocks written to the disk are kept in memory.
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.PP
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When setting disk geometry with the
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.B geometry
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control message,
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the arguments are
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sectors, sector size, cylinders, heads, and sectors per track.
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The last three may be zero for LBA disk simulations,
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but must be present.
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.PP
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The
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.B -f
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option causes
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.I disksim
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to use
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.I file
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as the initial contents of the disk rather than a zeroed image.
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Changes made to the disk are written back to
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.I file
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unless the
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.B -r
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option is given.
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.PP
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The
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.B -s
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option causes
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.I disksim
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to post its 9P service at
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.BI /srv/ service \fR.
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.SH EXAMPLES
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.I Disksim
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can be used to test programs such as
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.I fdisk
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and
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.IR prep (8)
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that expect
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.IR sd (3)
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disks:
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.IP
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.EX
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aux/disksim
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echo geometry 40000 512 0 0 0 >/dev/sdXX/ctl # 20MB
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disk/mbr /dev/sdXX/data
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disk/fdisk -baw /dev/sdXX/data
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disk/prep /dev/sdXX/plan9
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.EE
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.PP
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.I Disksim
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is useful for creating very large but mostly zeroed files
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for testing other programs.
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Test
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.IR tar (1)'s
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handling of large files:
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.IP
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.EX
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for(i in sdXX sdYY sdZZ) aux/disksim $i
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echo geometry 40000000 512 0 0 0 >/dev/sdXX/ctl # 20GB
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echo geometry 10000000 512 0 0 0 >/dev/sdYY/ctl # 5GB
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echo geometry 20000000 512 0 0 0 >/dev/sdZZ/ctl # 10GB
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tar cf /dev/sdXX/data /dev/sdYY/data /dev/sdZZ/data
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tar tvf /dev/sdXX/data
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.EE
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.SH SOURCE
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.B /sys/src/cmd/aux/disksim.c
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.SH SEE ALSO
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.IR sd (3),
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.IR prep (8)