.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
.B /dev/sdXX ).
The disk is initialized to zeros;
non-zeroed blocks written to the disk are kept in memory.
.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/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)