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