ZRAMCTL(8)		     System Administration		    ZRAMCTL(8)

NAME
       zramctl - set up and control zram devices

SYNOPSIS
       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]

DESCRIPTION
       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.

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

	   The list of supported algorithms could be inaccurate as it depends
	   on the current kernel configuration. A basic overview can be
	   obtained by using the command "cat
	   /sys/block/zram0/comp_algorithm"; however, please note that this
	   list might also be incomplete. This is due to the fact that ZRAM
	   utilizes the Crypto API, and if certain algorithms were built as
	   modules, it becomes impossible to enumerate all of them.

       -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.

	   The default list of columns may be extended if list is specified in
	   the format +list (e.g., zramctl -o+COMP-RATIO).

       -p, --algorithm-params
	   Set the algorithm parameters, for example, level=9
	   dict=/etc/dictionary to set compression level and pre-trained
	   dictionary. Parameters are algorithm specific.

       --output-all
	   Output all available columns.

       --raw
	   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 bytes.

	   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
	   Display version and exit.

EXIT STATUS
       zramctl returns 0 on success, nonzero on failure.

FILES
       /dev/zram[0..N]
	   zram block devices

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

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

AUTHORS
       Timofey Titovets <nefelim4ag@gmail.com>, Karel Zak <kzak@redhat.com>

SEE ALSO
       Linux kernel documentation
       <https://docs.kernel.org/admin-guide/blockdev/zram.html>

REPORTING BUGS
       For bug reports, use the issue tracker
       <https://github.com/util-linux/util-linux/issues>.

AVAILABILITY
       The zramctl command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.

util-linux 2.41.2		  2025-09-22			    ZRAMCTL(8)