The Linux Daily

sfdisk: The Scriptable fdisk

There was a brief mention of scripting partition editing in my post a couple of days ago about setting up an SD card for a Beagle Board. I revisited the script that was used to prepare the SD card partitions, took a closer look at it, and figured it was important enough to give it a mention in it’s own post — sfdisk.

Simply put, sfdisk is a scriptable fdisk which allows you to automate steps taken to create a partition layout. Here’s the standard blurb from the man page:

sfdisk has four (main) uses: list the size of a partition, list the partitions on a device, check the partitions on a device, and – very dangerous – repartition a device.

sfdisk accepts commands from stdin and the format is mostly comma separated for each field that is available which is:

<start> <size> <id> <bootable> <c,h,s> <c,h,s>

Be sure to check the man page for more information (as always). One quick example is presented in the man page:

sfdisk /dev/hdc << EOF
0,407
,407
;
;
EOF

Since the Beagle Board SD card setup script by XorA gave such a great usage example, I’d like to present it here again in case you missed it, except in a minimal form to avoid distractions:

#!/bin/sh
# Example Usage: create_sd /dev/sdb

DRIVE=$1

dd if=/dev/zero of=$DRIVE bs=1024 count=1024

SIZE=`fdisk -l $DRIVE | grep Disk | awk '{print $5}'`

echo DISK SIZE - $SIZE bytes

CYLINDERS=`echo $SIZE/255/63/512 | bc`

echo CYLINDERS - $CYLINDERS

{
echo ,9,0x0C,*
echo ,,,-
} | sfdisk -D -H 255 -S 63 -C $CYLINDERS $DRIVE

mkfs.vfat -F 32 -n "boot" ${DRIVE}1
mke2fs -j -L "rootfs" ${DRIVE}2

Have fun with it! While you’re at it, you may want to check out the parted command with the --script option. It’s very handy if you work with disk partitions frequently.