zramctl(8)

1ZRAMCTL(8)                   System Administration                  ZRAMCTL(8)
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NAME

6       zramctl - set up and control zram devices
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SYNOPSIS

9       Get info:
10           zramctl [options]
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12       Reset zram:
13           zramctl -r zramdev...
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15       Print name of first unused zram device:
16           zramctl -f
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18       Set up a zram device:
19           zramctl [-f | zramdev] [-s size] [-t number] [-a algorithm]
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DESCRIPTION

22       zramctl is used to quickly set up zram device parameters, to reset zram
23       devices, and to query the status of used zram devices.
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25       If no option is given, all non-zero size zram devices are shown.
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27       Note that zramdev node specified on command line has to already exist.
28       The command zramctl creates a new /dev/zram<N> nodes only when --find
29       option specified. It’s possible (and common) that after system boot
30       /dev/zram<N> nodes are not created yet.
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OPTIONS

33       -a, --algorithm lzo|lz4|lz4hc|deflate|842|zstd
34           Set the compression algorithm to be used for compressing data in
35           the zram device.
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37       -f, --find
38           Find the first unused zram device. If a --size argument is present,
39           then initialize the device.
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41       -n, --noheadings
42           Do not print a header line in status output.
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44       -o, --output list
45           Define the status output columns to be used. If no output
46           arrangement is specified, then a default set is used. Use --help to
47           get a list of all supported columns.
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49       --output-all
50           Output all available columns.
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52       --raw
53           Use the raw format for status output.
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55       -r, --reset
56           Reset the options of the specified zram device(s). Zram device
57           settings can be changed only after a reset.
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59       -s, --size size
60           Create a zram device of the specified size. Zram devices are
61           aligned to memory pages; when the requested size is not a multiple
62           of the page size, it will be rounded up to the next multiple. When
63           not otherwise specified, the unit of the size parameter is bytes.
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65           The size argument may be followed by the multiplicative suffixes
66           KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB,
67           ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning
68           as "KiB") or the suffixes KB (=1000), MB (=1000*1000), and so on
69           for GB, TB, PB, EB, ZB and YB.
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71       -t, --streams number
72           Set the maximum number of compression streams that can be used for
73           the device. The default is use all CPUs and one stream for kernels
74           older than 4.6.
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76       -h, --help
77           Display help text and exit.
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79       -V, --version
80           Print version and exit.
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EXIT STATUS

83       zramctl returns 0 on success, nonzero on failure.
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FILES

86       /dev/zram[0..N]
87           zram block devices
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EXAMPLE

90       The following commands set up a zram device with a size of one gigabyte
91       and use it as swap device.
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93            # zramctl --find --size 1024M
94            /dev/zram0
95            # mkswap /dev/zram0
96            # swapon /dev/zram0
97            ...
98            # swapoff /dev/zram0
99            # zramctl --reset /dev/zram0
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AUTHORS

102       Timofey Titovets <nefelim4ag@gmail.com>, Karel Zak <kzak@redhat.com>
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REPORTING BUGS

109       For bug reports, use the issue tracker at
110       https://github.com/util-linux/util-linux/issues.
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AVAILABILITY

113       The zramctl command is part of the util-linux package which can be
114       downloaded from Linux Kernel Archive
115       <https://www.kernel.org/pub/linux/utils/util-linux/>.
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119util-linux 2.38                   2022-02-17                        ZRAMCTL(8)