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#!/bin/bash
# This script does the following:
# zramswap start:
# Space is assigned to the zram device, then swap is initialized and enabled.
# zramswap stop:
# Somewhat potentially dangerous, removes zram module at the end
# https://github.com/torvalds/linux/blob/master/Documentation/blockdev/zram.txt
readonly CONFIG="/etc/default/zramswap"
readonly SWAP_DEV="/dev/zram0"
if command -v logger >/dev/null; then
function elog {
logger -s "Error: $*"
exit 1
}
function wlog {
logger -s "$*"
}
else
function elog {
echo "Error: $*"
exit 1
}
function wlog {
echo "$*"
}
fi
function start {
wlog "Starting Zram"
# Load config
test -r "${CONFIG}" || wlog "Cannot read config from ${CONFIG} continuing with defaults."
source "${CONFIG}" 2>/dev/null
# Set defaults if not specified
: "${ALGO:=lz4}" "${SIZE:=256}" "${PRIORITY:=100}"
SIZE=$((SIZE * 1024 * 1024)) # convert amount from MiB to bytes
# Prefer percent if it is set
if [ -n "${PERCENT}" ]; then
readonly TOTAL_MEMORY=$(awk '/MemTotal/{print $2}' /proc/meminfo) # in KiB
readonly SIZE="$((TOTAL_MEMORY * 1024 * PERCENT / 100))"
fi
modprobe zram || elog "inserting the zram kernel module"
echo -n "${ALGO}" > /sys/block/zram0/comp_algorithm || elog "setting compression algo to ${ALGO}"
echo -n "${SIZE}" > /sys/block/zram0/disksize || elog "setting zram device size to ${SIZE}"
mkswap "${SWAP_DEV}" || elog "initialising swap device"
swapon -p "${PRIORITY}" "${SWAP_DEV}" || elog "enabling swap device"
}
function status {
test -x "$(which zramctl)" || elog "install zramctl for this feature"
test -b "${SWAP_DEV}" || elog "${SWAP_DEV} doesn't exist"
# old zramctl doesn't have --output-all
#zramctl --output-all
zramctl "${SWAP_DEV}"
}
function stop {
wlog "Stopping Zram"
test -b "${SWAP_DEV}" || wlog "${SWAP_DEV} doesn't exist"
swapoff "${SWAP_DEV}" 2>/dev/null || wlog "disabling swap device: ${SWAP_DEV}"
modprobe -r zram || elog "removing zram module from kernel"
}
function usage {
cat << EOF
Usage:
zramswap (start|stop|restart|status)
EOF
}
case "$1" in
start) start;;
stop) stop;;
restart) stop && start;;
status) status;;
"") usage;;
*) elog "Unknown option $1";;
esac
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