This script initializes and manages compressed swap devices using zram to improve performance on Linux systems. It determines the number of zram devices to create based on CPU cores, allocates storage space for each based on available RAM, initializes the devices, creates swap filesystems on them, and activates the swap spaces. It also stops the zram devices and removes the zram kernel module.

1. #!/bin/bash
### BEGIN INIT INFO
# Provides: zram
# Required-Start:
# Required-Stop:
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Increased Performance In Linux With zRam (Virtual Swap
Compressed in RAM)
# Description: Adapted from systemd scripts at
https://github.com/mystilleef/FedoraZram
### END INIT INFO
DEFAULTS="/etc/default/zram"
# Include defaults if available
[ -r "$DEFAULTS" ] && . "$DEFAULTS"
# Get lsb functions
. /lib/lsb/init-functions
start() {
# Add support of defaults file parameter - ZRAM_NDEVS
if [ -z "$ZRAM_NDEVS" ] || [ "$ZRAM_NDEVS" -le "0" ]; then
# get the number of CPUs
num_cpus=$(grep -c processor /proc/cpuinfo)
else
# or just use user specified
num_cpus=$ZRAM_NDEVS
fi
# if something goes wrong, assume we have 1
[ "$num_cpus" != 0 ] || num_cpus=1
decr_num_cpus=$((num_cpus - 1))
# find module and it's param name
error_file=$(mktemp ${RC_NAME}XXXXXX) # storage for error message
param_name=$(/usr/bin/env modinfo --parameters zram 2>$error_file | head -1
| cut -d: -f1)
error_message=$(<$error_file)
rm -f $error_file
mod_found=$?
# load dependency modules
if [ "$mod_found" == 0 ]; then
log_begin_msg "Loading zRAM kernel module"
modprobe zram "$param_name=$num_cpus"
log_end_msg $?
else
log_failure_msg "Failed to load zRAM kernel module: ${error_message}"
# shit happens, yep.
exit $mod_found
fi
# get the amount of memory in the machine
mem_total_kb=$(fgrep MemTotal /proc/meminfo | grep -E --only-matching
'[[:digit:]]+')
mem_total=$((mem_total_kb * 1024))
# Add support of defaults file parameter - ZRAM_USE_PERCENT
if [ -z "$ZRAM_USE_PERCENT" ] || [ "$ZRAM_USE_PERCENT" -le "0" ] ||

2. [ "$ZRAM_USE_PERCENT" -gt "100" ]; then
# use 100% of ram for zRAM storage (suitable for low-ram laptops)
use_percent=100
else
# or just use user specified
use_percent=$ZRAM_USE_PERCENT
fi
zsize=$((use_percent * mem_total / num_cpus / 100))
# initialize the devices
for i in $(seq 0 $decr_num_cpus); do
echo $zsize > /sys/block/zram$i/disksize
done
# get page size
page_size=$(/usr/bin/env getconf PAGESIZE || /usr/bin/env getconf PAGE_SIZE)
# Creating swap filesystems
for i in $(seq 0 $decr_num_cpus); do
msg="> Making swap on /dev/zram$i"
mkswap -p $page_size /dev/zram$i 2>&1 >/dev/null
[ "$?" -eq "0" ] && log_success_msg $msg || log_failure_msg $msg
done
# Switch the swaps on
for i in $(seq 0 $decr_num_cpus); do
msg=">> Activating swap on /dev/zram$i"
swapon -p 100 /dev/zram$i
[ "$?" -eq "0" ] && log_success_msg $msg || log_failure_msg $msg
done
# TODO FIXME need strict error reporting
# log_end_msg 0
}
stop() {
# Switching off swap ASAP
for zswap in $(fgrep /dev/zram /proc/swaps | cut -d' ' -f1); do
swapoff $zswap
done
# Custom kernels can contain zram compiled-in
[ -z "$(fgrep zram /proc/modules)" ] || rmmod zram
}
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
sleep 3
start
;;
*)
echo "Usage: $0 {start|stop|restart}"
RETVAL=1
esac