From Fedora Project Wiki

Description

Test stopping the swap-on-zram service temporarily.

Setup

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

How to test

  1. Stop the swap-on-zram service:
    sudo systemctl stop swap-create@zram0.service
  2. Confirm it's stopped. The service should be marked as "inactive (dead)":
    $ 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: inactive (dead) since Sun 2020-06-28 19:32:07 MDT; 3s ago
           Docs: man:zram-generator(8)
                 man:zram-generator.conf(5)
        Process: 646 ExecStart=/usr/lib/systemd/system-generators/zram-generator --setup-device zram0 (code=exited, status=0/SUCCESS)
        Process: 1565 ExecStop=/usr/lib/systemd/system-generators/zram-generator --reset-device zram0 (code=exited, status=0/SUCCESS)
       Main PID: 646 (code=exited, status=0/SUCCESS)
            CPU: 25ms
    
    Jun 28 19:24:57 fmac.local systemd[1]: Starting Create swap on /dev/zram0...
    Jun 28 19:24:57 fmac.local zram-generator[648]: Setting up swapspace version 1, size = 3.8 GiB (4105170944 bytes)
    Jun 28 19:24:57 fmac.local zram-generator[648]: no label, UUID=03831cdf-96df-4a7a-a6c2-3bc8406f33f3
    Jun 28 19:24:57 fmac.local systemd[1]: Finished Create swap on /dev/zram0.
    Jun 28 19:32:07 fmac.local systemd[1]: Stopping Create swap on /dev/zram0...
    Jun 28 19:32:07 fmac.local systemd[1]: swap-create@zram0.service: Succeeded.
    Jun 28 19:32:07 fmac.local systemd[1]: Stopped Create swap on /dev/zram0.
    

    zramctl should list no device:

    $ zramctl
    

    swapon should only list your disk swap partitions and no /dev/zram0 device:

    $ swapon
    NAME      TYPE       SIZE USED PRIO
    /dev/sda5 partition 10.4G   0B   -2
    
  3. Start the swap-on-zram service again and confirm it's running:
    $ sudo systemctl start swap-create@zram0.service
    $ 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 19:32:54 MDT; 3s ago
           Docs: man:zram-generator(8)
                 man:zram-generator.conf(5)
        Process: 1580 ExecStart=/usr/lib/systemd/system-generators/zram-generator --setup-device zram0 (code=exited, status=0/SUCCESS)
       Main PID: 1580 (code=exited, status=0/SUCCESS)
            CPU: 33ms
    
    Jun 28 19:32:54 fmac.local systemd[1]: Starting Create swap on /dev/zram0...
    Jun 28 19:32:54 fmac.local zram-generator[1582]: Setting up swapspace version 1, size = 3.8 GiB (4105170944 bytes)
    Jun 28 19:32:54 fmac.local zram-generator[1582]: no label, UUID=f046c6d8-3f69-4f21-81ae-a7b1555891d9
    Jun 28 19:32:54 fmac.local systemd[1]: Finished Create swap on /dev/zram0.
    

Expected Results

  1. Stopping the service should work without issues and it should remove the /dev/zram0 device, i.e. it will no longer be visible in zramctl and swapon commands output.