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The sysctl command is used to dynamically modify kernel run parameters while the kernel is running, and the available kernel parameters are in the directory / proc/sys.

It includes some advanced options for TCP/ip stacks and virtual memory systems, which allow experienced administrators to improve eye-catching system performance. You can read and set more than five hundred system variables with sysctl.

Syntax:

Sysctl (option) (parameter)

Options:

-n: keywords are not printed when printing values

-e: ignore unknown keyword errors

-N: print name only

-w: use this when changing the sysctl setting

-p: load kernel parameter settings from the configuration file "/ etc/sysctl.conf"

-a: print all currently available kernel parameter variables and values

-A: prints all currently available kernel parameter variables and values in tabular form.

The meaning of common parameters:

-w temporarily change the value of a specified parameter, such as sysctl-w net.ipv4.ip_forward=1

-a displays all system parameters

-p loads system parameters from the specified file, or from / etc/sysctl.conf if not specified

If you just want to change the value of a system parameter temporarily, you can do it in two ways, such as enabling IP routing forwarding:

1) # echo 1 > / proc/sys/net/ipv4/ip_forward

2) # sysctl-w net.ipv4.ip_forward=1

Both of the above methods may turn on the routing function immediately, but if the system is rebooted or the # service network restart command is executed, the set value will be lost. If you want to keep the configuration permanently, you can modify the / etc/sysctl.conf file.

Change net.ipv4.ip_forward=0 to net.ipv4.ip_forward=1

1, the function of the sysctl command

Configure kernel parameters at run time

2. Examples of usage:

-w use this option to change a sysctl setting example: sysctl-w net.ipv4.ip_forward=1

-p load sysctl configuration file if no path is specified after-p, load / etc/sysctl.conf

Example: sysctl-p / etc/sysctl.conf

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