1SYSCTL(8) System Administration SYSCTL(8)
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6 sysctl - configure kernel parameters at runtime
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9 sysctl [options] [variable[=value]] [...]
10 sysctl -p [file or regexp] [...]
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13 sysctl is used to modify kernel parameters at runtime. The parameters
14 available are those listed under /proc/sys/. Procfs is required for
15 sysctl support in Linux. You can use sysctl to both read and write
16 sysctl data.
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19 variable
20 The name of a key to read from. An example is kernel.ostype.
21 The '/' separator is also accepted in place of a '.'.
22 variable=value
24 To set a key, use the form variable=value where variable is the
25 key and value is the value to set it to. If the value contains
26 quotes or characters which are parsed by the shell, you may need
27 to enclose the value in double quotes.
28 -n, --values
30 Use this option to disable printing of the key name when print‐
31 ing values.
32 -e, --ignore
34 Use this option to ignore errors about unknown keys.
35 -N, --names
37 Use this option to only print the names. It may be useful with
38 shells that have programmable completion.
39 -q, --quiet
41 Use this option to not display the values set to stdout.
42 -w, --write
44 Use this option when all arguments prescribe a key to be set.
45 -p[FILE], --load[=FILE]
47 Load in sysctl settings from the file specified or
48 /etc/sysctl.conf if none given. Specifying - as filename means
49 reading data from standard input. Using this option will mean
50 arguments to sysctl are files, which are read in the order they
51 are specified. The file argument may be specified as regular
52 expression.
53 -a, --all
55 Display all values currently available.
56 --deprecated
58 Include deprecated parameters to --all values listing.
59 -b, --binary
61 Print value without new line.
62 --system
64 Load settings from all system configuration files. See the SYS‐
65 TEM FILE PRECEDENCE section below.
66 -r, --pattern pattern
68 Only apply settings that match pattern. The pattern uses ex‐
69 tended regular expression syntax.
70 -A Alias of -a
72 -d Alias of -h
74 -f Alias of -p
76 -X Alias of -a
78 -o Does nothing, exists for BSD compatibility.
80 -x Does nothing, exists for BSD compatibility.
82 -h, --help
84 Display help text and exit.
85 -V, --version
87 Display version information and exit.
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90 When using the --system option, sysctl will read files from directories
91 in the following list in given order from top to bottom. Once a file of
92 a given filename is loaded, any file of the same name in subsequent di‐
93 rectories is ignored.
94 /etc/sysctl.d/*.conf
96 /run/sysctl.d/*.conf
97 /usr/local/lib/sysctl.d/*.conf
98 /usr/lib/sysctl.d/*.conf
99 /lib/sysctl.d/*.conf
100 /etc/sysctl.conf
101 All configuration files are sorted in lexicographic order, regardless
103 of the directory they reside in. Configuration files can either be com‐
104 pletely replaced (by having a new configuration file with the same name
105 in a directory of higher priority) or partially replaced (by having a
106 configuration file that is ordered later).
107
109 /sbin/sysctl -a
110 /sbin/sysctl -n kernel.hostname
111 /sbin/sysctl -w kernel.domainname="example.com"
112 /sbin/sysctl -p/etc/sysctl.conf
113 /sbin/sysctl -a --pattern forward
114 /sbin/sysctl -a --pattern forward$
115 /sbin/sysctl -a --pattern 'net.ipv4.conf.(eth|wlan)0.arp'
116 /sbin/sysctl --pattern '^net.ipv6' --system
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119 The base_reachable_time and retrans_time are deprecated. The sysctl
120 command does not allow changing values of these parameters. Users who
121 insist to use deprecated kernel interfaces should push values to /proc
122 file system by other means. For example:
123 echo 256 > /proc/sys/net/ipv6/neigh/eth0/base_reachable_time
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127 /proc/sys
128 /etc/sysctl.d/*.conf
129 /run/sysctl.d/*.conf
130 /usr/local/lib/sysctl.d/*.conf
131 /usr/lib/sysctl.d/*.conf
132 /lib/sysctl.d/*.conf
133 /etc/sysctl.conf
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136 sysctl.conf(5) regex(7)
137
139 George Staikos ⟨staikos@0wned.org⟩
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142 Please send bug reports to ⟨procps@freelists.org⟩
143procps-ng 2023-01-16 SYSCTL(8)