Linux man pages

Section (8) zramctl

Linux manual pages	Section 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_zsingle_quotesz_s possible (and common) that after system boot /dev/zram<N> nodes are not created yet.

OPTIONS

−a, −−algorithm lzo|lz4|lz4hc|deflate|842: 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: 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 one stream.
−V, −−version: Display version information and exit.
−h, −−help: Display help text and exit.

RETURN VALUE

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 <[email protected]>
Karel Zak <[email protected]>

AVAILABILITY

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