2016年1月

先看它是干嘛用的
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$ man sysctl
SYSCTL(8) SYSCTL(8)

NAME
sysctl - configure kernel parameters at runtime

SYNOPSIS
sysctl [-n] [-e] variable ...
sysctl [-n] [-e] [-q] -w variable=value ...
sysctl [-n] [-e] [-q] -p <filename>
sysctl [-n] [-e] -a
sysctl [-n] [-e] -A

DESCRIPTION
sysctl is used to modify kernel parameters at runtime. The parameters available are those listed under /proc/sys/. Procfs is required for sysctl(8) support in Linux. You can use sysctl(8) to both
read and write sysctl data.

PARAMETERS
variable
The name of a key to read from. An example is kernel.ostype. The ’/’ separator is also accepted in place of a ’.’.

variable=value
To set a key, use 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.

-n Use this option to disable printing of the key name when printing values.

-e Use this option to ignore errors about unknown keys.

-N Use this option to only print the names. It may be useful with shells that have programmable completion.

-q Use this option to not display the values set to stdout.

-w Use this option when you want to change a sysctl setting.

-p Load in sysctl settings from the file specified or /etc/sysctl.conf if none given. Specifying - as filename means reading data from standard input.

-a Display all values currently available.

-A Same as -a

EXAMPLES
/sbin/sysctl -a

/sbin/sysctl -n kernel.hostname

/sbin/sysctl -w kernel.domainname="example.com"

/sbin/sysctl -p /etc/sysctl.conf

NOTES
Please note that modules loaded after sysctl is run may override the settings (example: sunrpc.* settings are overridden when the sunrpc module is loaded). This may cause some confusion during boot
when the settings in sysctl.conf may be overriden. To prevent such a situation, sysctl must be run after the particular module is loaded (e.g., from /etc/rc.d/rc.local or by using the install direc-
tive in modprobe.conf)

FILES
/proc/sys /etc/sysctl.conf

SEE ALSO
sysctl.conf(5), modprobe.conf(5)

AUTHOR
George Staikos, <[email protected]>

21 Sep 1999 SYSCTL(8)
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