disksim - disk simulator aux/disksim [ -r ] [ -f file ] [ -s srvname ] [ -m mtpt ] [ diskname ] Disksim presents an in-memory disk in the manner of the sd (3) device on mtpt / diskname (default /dev/sdXX ). The disk is initialized to zeros; non-zeroed blocks written to the disk are kept in memory.

The -f option causes disksim to use file as the initial contents of the disk rather than a zeroed image. Changes made to the disk are written back to file unless the -r option is given.

The -s option causes disksim to post its 9P service at /srv/ service .

Disksim can be used to test programs such as fdisk and prep (8) that expect sd (3) disks: .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

Disksim is useful for creating very large but mostly zeroed files for testing other programs. Test tar (1)'s handling of large files:

.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 /sys/src/cmd/aux/disksim.c sd (3), prep (8)