Provided by: util-linux_2.38-4ubuntu1_amd64 bug


       zramctl - set up and control zram devices


       Get info:
           zramctl [options]

       Reset zram:
           zramctl -r zramdev...

       Print name of first unused zram device:
           zramctl -f

       Set up a zram device:
           zramctl [-f | zramdev] [-s size] [-t number] [-a algorithm]


       zramctl is used to quickly set up zram device parameters, to reset zram devices, and to
       query the status of used zram devices.

       If no option is given, all non-zero size zram devices are shown.

       Note that zramdev node specified on command line has to already exist. The command zramctl
       creates a new /dev/zram<N> nodes only when --find option specified. It’s possible (and
       common) that after system boot /dev/zram<N> nodes are not created yet.


       -a, --algorithm lzo|lz4|lz4hc|deflate|842|zstd
           Set the compression algorithm to be used for compressing data in the zram device.

       -f, --find
           Find the first unused zram device. If a --size argument is present, then initialize
           the device.

       -n, --noheadings
           Do not print a header line in status output.

       -o, --output list
           Define the status output columns to be used. If no output arrangement is specified,
           then a default set is used. Use --help to get a list of all supported columns.

           Output all available columns.

           Use the raw format for status output.

       -r, --reset
           Reset the options of the specified zram device(s). Zram device settings can be changed
           only after a reset.

       -s, --size size
           Create a zram device of the specified size. Zram devices are aligned to memory pages;
           when the requested size is not a multiple of the page size, it will be rounded up to
           the next multiple. When not otherwise specified, the unit of the size parameter is

           The size argument may be followed by the multiplicative suffixes KiB (=1024), MiB
           (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional,
           e.g., "K" has the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000),
           and so on for GB, TB, PB, EB, ZB and YB.

       -t, --streams number
           Set the maximum number of compression streams that can be used for the device. The
           default is use all CPUs and one stream for kernels older than 4.6.

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.


       zramctl returns 0 on success, nonzero on failure.


           zram block devices


       The following commands set up a zram device with a size of one gigabyte and use it as swap

            # zramctl --find --size 1024M
            # mkswap /dev/zram0
            # swapon /dev/zram0
            # swapoff /dev/zram0
            # zramctl --reset /dev/zram0


       Timofey Titovets <>, Karel Zak <>


       Linux kernel documentation


       For bug reports, use the issue tracker at


       The zramctl command is part of the util-linux package which can be downloaded from Linux
       Kernel Archive <>.