From Fedora Project Wiki


Test swap-on-zram with a custom configuration.


  1. Make sure your system has swap-on-zram installed and enabled.

How to test

  1. Create a custom configuration file, which will override the default configuration file:
    sudo cp /usr/share/doc/zram-generator/zram-generator.conf.example /etc/systemd/zram-generator.conf
  2. Edit the configuration file, read the included documentation, and set custom values. (Pay attention to host-memory-limit, if you have more total memory than this value, the zram device will not get created at all).
    sudo nano /etc/systemd/zram-generator.conf
  3. Restart the swap-on-zram service to apply your changes:
    sudo systemctl restart swap-create@zram0.service
  4. Confirm the swap-on-zram service was run correctly (its status is active (exited)):
    $ sudo systemctl status swap-create@zram0.service
    ● swap-create@zram0.service - Create swap on /dev/zram0
         Loaded: loaded (/usr/lib/systemd/system/swap-create@.service; static; vendor preset: disabled)
         Active: active (exited) since Sun 2020-06-28 19:52:48 MDT; 1min 0s ago
           Docs: man:zram-generator(8)
        Process: 650 ExecStart=/usr/lib/systemd/system-generators/zram-generator --setup-device zram0 (code=exited, status=0/SUCCESS)
       Main PID: 650 (code=exited, status=0/SUCCESS)
            CPU: 28ms
    Jun 28 19:52:48 fmac.local systemd[1]: Starting Create swap on /dev/zram0...
    Jun 28 19:52:48 fmac.local zram-generator[653]: Setting up swapspace version 1, size = 512 MiB (536866816 bytes)
    Jun 28 19:52:48 fmac.local zram-generator[653]: no label, UUID=72991b9c-f8fd-459c-9bb8-6e8ac19a16c2
    Jun 28 19:52:48 fmac.local systemd[1]: Finished Create swap on /dev/zram0.
  5. Look at zramctl and swapon output and confirm the zram device is configured according to your custom values you've set in the configuration file.
    $ zramctl
    /dev/zram0 lzo-rle       512M   4K   73B   12K       8 [SWAP]
    $ swapon
    NAME       TYPE       SIZE USED PRIO
    /dev/sda5  partition 10.4G   0B   -2
    /dev/zram0 partition  512M   0B  100
  6. After you verified this test case, return back to the original state by deleting the custom configuration file and again restarting the service (or rebooting):
    sudo rm /etc/systemd/zram-generator.conf
    sudo systemctl restart swap-create@zram0.service

Expected Results

  1. The swap-on-zram service should start correctly.
  2. The values you set in the configuration file should correctly affect the zram swap device (size, algorithm, whether it exists at all, etc).