Sysctl

sysctl - Configure kernel parameters at runtime

Beschreibung

• sysctl is used to modify kernel parameters at runtime
• The parameters available are those listed under /proc/sys/
• Procfs is required for sysctl support in Linux. You can use sysctl to both read and write sysctl data

Aufruf

sysctl [options] [variable[=value]] [...]
sysctl -p [file or regexp] [...]

variable

• is the name of a key to read from.
• An example is kernel.ostype. The '/' separator is also accepted in place of a '.'.

variable=value

• is used to set a key, in the form variable=value where variable is the key and value is the value to set it to.
• If the value contains quotes or characters which are parsed by the shell, you may need to enclose the value in double quotes. This requires the -w parameter to use

Optionen

Unix	GNU	Parameter	Beschreibung
-n	--values		Disable printing of the key name when printing values
-e	--ignore		Ignore errors about unknown keys
-N	--names		Only print the names. It may be useful with shells that have programmable completion
-q	--quiet		Do not display the values set to stdout
-w	--write		Change a sysctl setting
-p	--load	[=FILE]	Load in sysctl settings from the file specified or /etc/sysctl.conf if none given. Specifying - as filename means reading data from standard input. Using this option will mean arguments to sysctl are files, which are read in the order they are specified. The file argument may be specified as regular expression
-a	--all		Display all values currently available
	--deprecated		Include deprecated parameters to --all values listing
-b	--binary		Print value without new line
	--system		Load settings from all system configuration files. /run/sysctl.d/*.conf /etc/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf
-r	--pattern pattern		Only apply settings that match pattern. The pattern uses extended regular expression syntax
-A			Alias of -a
-d			Alias of -h
-f			Alias of -p
-X			Alias of -a
-o			Does nothing, exists for BSD compatibility
-x			Does nothing, exists for BSD compatibility
-h	--help		Display help text and exit
-V	--version		Display version information and exit

Anwendung

/sbin/sysctl -a
/sbin/sysctl -n kernel.hostname
/sbin/sysctl -w kernel.domainname="example.com"
/sbin/sysctl -p/etc/sysctl.conf
/sbin/sysctl -a --pattern forward
/sbin/sysctl -a --pattern forward$
/sbin/sysctl -a --pattern 'net.ipv4.conf.(eth|wlan)0.arp'
/sbin/sysctl --system --pattern '^net.ipv6'

Veraltete Parameter

• Die Parameter „base_reachable_time“ und „retrans_time“ sind veraltet
• Der Befehl „sysctl“ erlaubt keine Änderung der Werte dieser Parameter
• Benutzer, die unbedingt veraltete Kernel-Schnittstellen verwenden möchten, sollten die Werte auf andere Weise in das /proc-Dateisystem übertragen

Beispiel

echo 256 > /proc/sys/net/ipv6/neigh/eth0/base_reachable_time

Konfiguration

Dateien

Datei	Beschreibung
/proc/sys
/etc/sysctl.conf

Anhang

Siehe auch

• Sysctl
• Sysctl/Parameter
• Sysctl/Problembehebung

Dokumentation

Man-Page

• sysctl.conf(5)
• regex(7)

Links

Projekt

1. https://github.com/klaver/sysctl