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ZRAMCTL

Section: System Administration (8)
Updated: July 2014
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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.

-a, --algorithm lzo|lz4: 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.
--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 one stream.
-V, --version: Display version information and exit.
-h, --help: Display help text and exit.

zramctl returns 0 on success, nonzero on failure.

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

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

The zramctl command is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/.