haos-swapfile

#!/bin/sh
set -e

size2kilobytes() {
	bytes="$(echo "$1" | awk \
	  'BEGIN{IGNORECASE = 1}
	   function tobytes(n,b,p) {printf "%u\n", n*b^p/1024}
	   /[0-9]B?$/{tobytes($1,  1, 0); next};
	   /K(i?B)?$/{tobytes($1,  2, 10); next};
	   /M(i?B)?$/{tobytes($1,  2, 20); next};
	   /G(i?B)?$/{tobytes($1,  2, 30); next};
	   {print -1}')"
	echo "$bytes"
}

if [ -f /etc/default/haos-swapfile ]; then
    # shellcheck disable=SC1091
    . /etc/default/haos-swapfile
fi
SWAPFILE="/mnt/data/swapfile"

# Swap size in kilobytes (as it's also what meminfo shows)
SWAPSIZE="$(size2kilobytes "${SWAPSIZE}")"
SWAPSIZE_TOLERANCE=0

if [ -z "${SWAPSIZE}" ] || [ "${SWAPSIZE}" = "-1" ]; then
	# Default to 33% of total memory
	SWAPSIZE="$(awk '/MemTotal/{ print int($2 * 0.33) }' /proc/meminfo)"
	echo "[INFO] Using default swapsize of 33% RAM (${SWAPSIZE} kB)"
	SWAPSIZE_TOLERANCE=$((32*1024))  # allow for 32MB fluctuations
fi

# Swap space in 4k blocks
SWAPSIZE_BLOCKS=$((SWAPSIZE / 4))

if [ "${SWAPSIZE_BLOCKS}" -lt 10 ]; then
    echo "[INFO] Requested swap size smaller than 40kB, disabling swap"

    if [ -f "${SWAPFILE}" ]; then
        echo "[INFO] Removing existing swapfile"
        rm -f "${SWAPFILE}"
    fi

    exit 0
fi

CURRENT_SIZE="$([ -f "${SWAPFILE}" ] && stat "${SWAPFILE}" -c '%s' || echo 0)"

if [ -s "${SWAPFILE}" ] && [ "${CURRENT_SIZE}" -ge $(((SWAPSIZE - SWAPSIZE_TOLERANCE) * 1024)) ] \
    && [ "${CURRENT_SIZE}" -le $(((SWAPSIZE + SWAPSIZE_TOLERANCE) * 1024)) ]; then
    echo "[INFO] Swapfile already exists with size ${CURRENT_SIZE} bytes"
elif [ ! -s "${SWAPFILE}" ] || [ "${CURRENT_SIZE}" -ne $((SWAPSIZE_BLOCKS * 4096)) ]; then
    # Check free space (in 4k blocks)
    if [ "$(stat -f /mnt/data -c '%f')" -lt "${SWAPSIZE_BLOCKS}" ]; then
        echo "[ERROR] Not enough space to allocate swapfile"
        exit 1
    fi

    echo "[INFO] Creating swapfile of size ${SWAPSIZE} kB (rounded to ${SWAPSIZE_BLOCKS} blocks)"
    umask 0077
    dd if=/dev/zero of="${SWAPFILE}" bs=4k count="${SWAPSIZE_BLOCKS}"
fi

if ! swaplabel "${SWAPFILE}" > /dev/null 2>&1; then
    /usr/lib/systemd/systemd-makefs swap "${SWAPFILE}"
fi