[Post-installation][How-to] Improve performance and stability with zRAM

What is zRAM and why this how-to (in few words)?

The goal of this how-to is to provide an almost out-of-the-box setup, with no file modification, few commands and easily revertible.
This page is not dedicated to full zRAM coverage and tuning, there are some other resources linked at the bottom of this topic.

By default zRAM is not activated in OpenMandriva Lx, but it has some benefits to use it.

zRAM allows to compress the RAM. Since the compression/decompression of RAM takes less time than the use of the hard disk in the form of virtual memory (known as the “swap disk”), this makes it possible to increase the responsiveness of a Linux system.

Also, as having a swap avoid full memory crash or hang, there are performance benefits using zRAM swap.

zRAM can exist alongside classic swap (file or partition): a classic case can be to use zRAM for almost all memory pages management and classic swap for hibernation and hybrid sleep. What is important is to give the higher priority to zRAM (swapon -s to see it, higher number means higher priority). By default zRAM has a higher priority in OpenMandriva Lx if installed.


Filename                                Type            Size            Used            Priority
/swapfile                               file            16051516        0               -2
/dev/zram0                              partition       4012028         853872          16383

If you simply want to use zRAM without having all the explanations, just read the following paragraph (Summary of the commands to execute) else read the detailed steps below.

Summary of the commands to execute

In case you’re in hurry, here are the commands. Detailed steps are below.

Open Konsole (or another terminal) and run

sudo dnf install zram-init
sudo modprobe zram
sudo systemctl start zram_swap.service
sudo systemctl start zram_tmp.service
sudo systemctl start zram_var_tmp.service
sudo systemctl enable zram_swap.service
sudo systemctl enable zram_tmp.service
sudo systemctl enable zram_var_tmp.service

Detailed steps


With few commands and a package including some convenient scripts, we will

  • activate zRAM module
  • setup a zRAM swap (used to get more stabilty and performance)
  • Add an extra layer of performance by using zRAM instead of tmpFS for /tmp and instead of local drive for /var/tmp)

Note: you can have both zRAM swap and traditional swap (partition or file), latter being used for storing not (or hardly) used memory pages, especially after long uptime, and even activate hibernation. There is another topic dedicated to swap.

Module activation

install zram-init

sudo dnf install zram-init

It will install several services and a new configuration file for zRAM kernel module at /etc/modprobe.d/zram.conf (which you can edit to tune your preference, if you know what you’re doing) . The module will automatically be enabled at boot. To activate it immediately, run

modprobe zram

optional: check module activation

Check that the module is activated with

lsmod| grep zram

which should provide that kind of output

zram 36864 4

services activation

Three new services are provided, each of them can be tuned by editing the files in /lib/systemd/system/:

  • zram_swap.service
  • zram_tmp.service
  • zram_var_tmp.service

Please refer to our systemd documentation if you want to know how to start/stop and enable/disable services.

Activate zRAM swap

sudo systemctl start zram_swap.service
sudo systemctl enable zram_swap.service

Optional: check swap is activated

swapon -s

which should provide that kind of output

Filename                                Type            Size            Used            Priority
/dev/zram0                              partition       4012028         0               16383

use zRAM for /etc and /var/etc

Optional: check configuration before

If you run df -h you should see that you have several drives on a temporary filesystem (tmpFS), and especially /tmp

tmpfs         2,0G     24K  2,0G   1% /tmp

Run the commands

Start and enable services

sudo systemctl start zram_tmp.service
sudo systemctl start zram_var_tmp.service
sudo systemctl enable zram_tmp.service
sudo systemctl enable zram_var_tmp.service

Optional, check configuration after

by running df -h, you should now see that both /tmp and /var/tmp are mounted on /dev/zram

/dev/zram1         2,0G     24K  2,0G   1% /tmp
/dev/zram2         2,0G     24K  2,0G   1% /var/tmp

Revert: unactivate and uninstall

Reverting mainly means stopping and disabling the services

sudo systemctl stop zram_swap.service
sudo systemctl stop zram_tmp.service
sudo systemctl stop zram_var_tmp.service
sudo systemctl disable zram_swap.service
sudo systemctl disable zram_tmp.service
sudo systemctl disable zram_var_tmp.service

You may also want to disable the zram module. You should uninstall zram-init and in case you made some tuning also delete the modprobe zram conf file.

sudo dnf remove zram-init
sudo rm /etc/modprobe.d/zram.conf


Interesting resources for zRAM