extend-filesystems

#!/bin/bash
# Automatic resize of btrfs and ext4 filesystems.
#
# The only partitions that may be considered:
#  - GPT partitions with the 'coreos-resize'
#  - Have a btrfs, ext4 or xfs filesystem mounted read-write
#  - Have at least 2MB of unpartitioned space to grow into (cgpt default)
#
# This last restriction means that if cgpt resize succeeds in extending
# the partition but the filesystem resize fails the operation will not
# be re-attempted by this script later unless the disk grows even more.

set -e -o pipefail

COREOS_RESIZE="3884dd41-8582-4404-b9a8-e9b84f2df50e"

declare -a DEV_LIST
mapfile DEV_LIST < <(lsblk -P -o NAME,PARTTYPE,FSTYPE,MOUNTPOINT)

for dev_info in "${DEV_LIST[@]}"; do
    eval "$dev_info"
    NAME=${NAME//\!//}
    if [[ "${PARTTYPE}" != "${COREOS_RESIZE}" ]] || \
       [[ -z "${NAME}" ]] || \
       [[ -z "${MOUNTPOINT}" ]] || \
       [[ ! -w "${MOUNTPOINT}" ]] || \
       [[ "${FSTYPE}" != "btrfs" && "${FSTYPE}" != "ext4" && "${FSTYPE}" != "xfs" ]]
    then
        continue
    fi

    device="/dev/${NAME}"
    old_size=$(blockdev --getsz "${device}")
    cgpt resize "${device}"

    # Only resize filesystem if the partition changed
    if [[ "${old_size}" -eq $(blockdev --getsz "${device}") ]]; then
        continue
    fi

    case "${FSTYPE}" in
        "btrfs")
            # map the device name to the btrfs device id
            device_id=$(btrfs filesystem show -d "${device}" | \
                        awk -v "d=${device}" -e 'd == $8 {print $2}')
            btrfs filesystem resize "${device_id}:max" "${MOUNTPOINT}"
            ;;
        "ext4")
            resize2fs "${device}"
            ;;
        "xfs")
            xfs_growfs "${MOUNTPOINT}"
            ;;
    esac
done