Scripting

Partitioning by script

A reader requested a demonstration of automatic partitioning. The task was to create partitions of fixed size and allow the last partition to consume remaining space. Since the calculations used in this exercise are revelatory of partitioning issues, the first version of the script is included below, in the hopes that it might be of use. This section will be expanded in Version 4 of this HOWTO.

#!/bin/sh

partitionSizes=( 1000000000 256000000 NA ) ; # size in bytes, NA=unspecified
partitionTypes=( 83 82 83 )               ; # see available types: sfdisk -T
partitionFlags=( bootable NA NA )
blockSize=1024
start=1

#---------------------------------------------------------------#
#          Do not modify contents below this line
#---------------------------------------------------------------#


function GetGeometry ()
 {
	numberOfBlocks=`sfdisk -s $1` || exit 1
	bytes=$(($numberOfBlocks * 1024))
	
	geometry=(`sfdisk -g $1`) || exit 1	
	cylinders=${geometry[1]}
	heads=${geometry[3]}
	sectors=${geometry[5]}
	
	
	cylinderSize=`echo "scale=4; $numberOfBlocks / $cylinders" | bc` || exit 1
 }


function WritePartitionInfo
 {
 	let partitionNumber=$index+1
 	
 	partitionFlag=${partitionFlags[$index]}
 	[ $partitionFlag != NA ] || partitionFlag=
 	
 	partitionType=${partitionTypes[$index]}
 	[ $partitionType != NA ] || partitionType=
 	
 	if [ ${partitionSizes[$index]} = "NA" ]
 	  then
 	  	cylindersNeeded=
 	  else
 	  	cylindersNeeded=`echo "${partitionSizes[$index]} / ( $cylinderSize * $blockSize )" | bc`
 	fi

	echo "${1}$partitionNumber : start=   $start,   size= $cylindersNeeded,	Id= $partitionType,	$partitionFlag" 
	echo "${1}$partitionNumber : start=   $start,   size= $cylindersNeeded,	Id= $partitionType,	$partitionFlag" >> $outputFile

	[ -z "$start" ] && start=0
	[ -z "$cylindersNeeded" ] && cylindersNeeded=0
	start=`echo "scale=4; $start + $cylindersNeeded + 1" | bc` || exit 1
 }


# ---------------------------------------------------------------------- #
# ------------------------       MAIN     ------------------------------ #
# ---------------------------------------------------------------------- #


[ $# -eq 1 ] || { echo "usage: auto_partition.sh device (e.g. /dev/hda)"; exit 1;}
[ -b $1 ] || { echo "$1 not a block device"; exit 1;}
outputFile=${1#/dev/}_proposed


GetGeometry $1

echo "bytes:     $bytes"
echo "blocks:    $numberOfBlocks"
echo "cylinders: $cylinders"
echo "heads:     $heads"
echo "sectors:   $sectors"



#echo "unit: cylinders" > $outputFile
> $outputFile

for index in `jot ${#partitionSizes[@]} 0`
 do
 	WritePartitionInfo 
 done


# This is it! Write the partition table
sfdisk /dev/sda --no-reread < sda_proposed