Resize partition to maximum using parted in non-interactive mode

HINT: this script is compatible with parted v3+ OOTB, if you have parted 2, you need to change parted resizepart to parted resize

lets put this into a script, the acualy command is a onliner, we just add a lot more to ensure the first 2 parameters are set:

#!/bin/bash
set -e

if [[ $# -eq 0 ]] ; then
    echo 'please tell me the device to resize as the first parameter, like /dev/sda'
    exit 1
fi


if [[ $# -eq 1 ]] ; then
    echo 'please tell me the partition number to resize as the second parameter, like 1 in case you mean /dev/sda1 or 4, if you mean /dev/sda2'
    exit 1
fi

DEVICE=$1
PARTNR=$2
APPLY=$3

fdisk -l $DEVICE$PARTNR >> /dev/null 2>&1 || (echo "could not find device $DEVICE$PARTNR - please check the name" && exit 1)

CURRENTSIZEB=`fdisk -l $DEVICE$PARTNR | grep "Disk $DEVICE$PARTNR" | cut -d' ' -f5`
CURRENTSIZE=`expr $CURRENTSIZEB / 1024 / 1024`
# So get the disk-informations of our device in question printf %s\\n 'unit MB print list' | parted | grep "Disk /dev/sda we use printf %s\\n 'unit MB print list' to ensure the units are displayed as MB, since otherwise it will vary by disk size ( MB, G, T ) and there is no better way to do this with parted 3 or 4 yet
# then use the 3rd column of the output (disk size) cut -d' ' -f3 (divided by space)
# and finally cut off the unit 'MB' with blanc using tr -d MB
MAXSIZEMB=`printf %s\\n 'unit MB print list' | parted | grep "Disk ${DEVICE}" | cut -d' ' -f3 | tr -d MB`

echo "[ok] would/will resize to from ${CURRENTSIZE}MB to ${MAXSIZEMB}MB "

if [[ "$APPLY" == "apply" ]] ; then
  echo "[ok] applying resize operation.."
  parted ${DEVICE} resizepart ${PARTNR} ${MAXSIZEMB}
  echo "[done]"
else
  echo "[WARNING]!: Sandbox mode, i did not size!. Use 'apply' as the 3d parameter to apply the changes"
fi

usage

Save the script above as resize.sh and make it executable

# resize the fourth partition to the maximum size, so /dev/sda4
# this is no the sandbox mode, so no changes are done
./resize.sh /dev/sda 4

# apply those changes
./resize.sh /dev/sda 4 apply

For example, in case you have a vg vgdata with a lv 'data' on /dev/sdb1 while using LVM, the whole story would look like

./resize.sh /dev/sdb 1 apply
pvresize /dev/sdb1
lvextend -r /dev/mapper/vgdata-data -l 100%FREE

Thats it, resized logical volume including resized filesystem ( -r ) - all done, check it with df -h :)

Explanation

What we use to find the disk size is

resizepart ${PARTNR} `parted -l | grep ${DEVICE} | cut -d' ' -f3 | tr -d MB

a) So get the disk-informations of our device in question printf %s\\n 'unit MB print list' | parted | grep "Disk /dev/sda we use printf %s\\n 'unit MB print list' to ensure the units are displayed as MB, since otherwise it will vary by disk size ( MB, G, T ) and there is no better way to do this with parted 3 or 4 yet

b) then use the 3rd column of the output (disk size) cut -d' ' -f3 (divided by space)

c) and finally cut off the unit 'MB' with blanc using tr -d MB

Follow ups

I published the script on https://github.com/EugenMayer/parted-auto-resize so if anything is to improved feature wise, use pull requests there ( anything not in scope of this question )