man/sysctl.d.5

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   2 .TH "SYSCTL\&.D" "5" "" "systemd 214" "sysctl.d"
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  20 .\" * MAIN CONTENT STARTS HERE *
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  22 .SH "NAME"
  23 sysctl.d \- Configure kernel parameters at boot
  24 .SH "SYNOPSIS"
  25 .PP
  26 /etc/sysctl\&.d/*\&.conf
  27 .PP
  28 /run/sysctl\&.d/*\&.conf
  29 .PP
  30 /usr/lib/sysctl\&.d/*\&.conf
  31 .SH "DESCRIPTION"
  32 .PP
  33 At boot,
  34 \fBsystemd-sysctl.service\fR(8)
  35 reads configuration files from the above directories to configure
  36 \fBsysctl\fR(8)
  37 kernel parameters\&.
  38 .SH "CONFIGURATION FORMAT"
  39 .PP
  40 The configuration files contain a list of variable assignments, separated by newlines\&. Empty lines and lines whose first non\-whitespace character is
  41 "#"
  42 or
  43 ";"
  44 are ignored\&.
  45 .PP
  46 Note that either
  47 "/"
  48 or
  49 "\&."
  50 may be used as separators within sysctl variable names\&. If the first separator is a slash, remaining slashes and dots are left intact\&. If the first separator is a dot, dots and slashes are interchanged\&.
  51 "kernel\&.domainname=foo"
  52 and
  53 "kernel/domainname=foo"
  54 are equivalent and will cause
  55 "foo"
  56 to be written to
  57 /proc/sys/kernel/domainname\&. Either
  58 "net\&.ipv4\&.conf\&.enp3s0/200\&.forwarding"
  59 or
  60 "net/ipv4/conf/enp3s0\&.200/forwarding"
  61 may be used to refer to
  62 /proc/sys/net/ipv4/conf/enp3s0\&.200/forwarding\&.
  63 .PP
  64 Each configuration file shall be named in the style of
  65 \fIprogram\fR\&.conf\&. Files in
  66 /etc/
  67 override files with the same name in
  68 /usr/lib/
  69 and
  70 /run/\&. Files in
  71 /run/
  72 override files with the same name in
  73 /usr/lib/\&. Packages should install their configuration files in
  74 /usr/lib/\&. Files in
  75 /etc/
  76 are reserved for the local administrator, who may use this logic to override the configuration files installed by vendor packages\&. All configuration files are sorted by their filename in lexicographic order, regardless of which of the directories they reside in\&. If multiple files specify the same variable name, the entry in the file with the lexicographically latest name will be applied\&. It is recommended to prefix all filenames with a two\-digit number and a dash, to simplify the ordering of the files\&.
  77 .PP
  78 If the administrator wants to disable a configuration file supplied by the vendor, the recommended way is to place a symlink to
  79 /dev/null
  80 in
  81 /etc/sysctl\&.d/
  82 bearing the same filename\&.
  83 .PP
  84 The settings configured with
  85 sysctl\&.d
  86 files will be applied early on boot\&. The network interface\-specific options will also be applied individually for each network interface as it shows up in the system\&. (More specifically,
  87 net\&.ipv4\&.conf\&.*,
  88 net\&.ipv6\&.conf\&.*,
  89 net\&.ipv4\&.neigh\&.*
  90 and
  91 net\&.ipv6\&.neigh\&.*)
  92 .SH "EXAMPLE"
  93 .PP
  94 \fBExample\ \&1.\ \&/etc/sysctl.d/domain-name.conf example:\fR
  95 .sp
  96 .if n \{\
  97 .RS 4
  98 .\}
  99 .nf
 100 # Set kernel YP domain name
 101 kernel\&.domainname=example\&.com
 102 .fi
 103 .if n \{\
 104 .RE
 105 .\}
 106 .SH "SEE ALSO"
 107 .PP
 108 \fBsystemd\fR(1),
 109 \fBsystemd-sysctl.service\fR(8),
 110 \fBsystemd-delta\fR(1),
 111 \fBsysctl\fR(8),
 112 \fBsysctl.conf\fR(5)