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
- 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.
zramctl returns 0 on success, nonzero on failure.
- /dev/zram[0..N]
- zram block devices
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/.