Sysctl

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sysctl (systemctl) allows the configuration of Kernel parameters at runtime.

Usage

Usage:
 sysctl [options] [variable[=value] ...]

Options:
  -a, --all            display all variables
  -A                   alias of -a
  -X                   alias of -a
      --deprecated     include deprecated parameters to listing
      --dry-run        Print the key and values but do not write
  -b, --binary         print value without new line
  -e, --ignore         ignore unknown variables errors
  -N, --names          print variable names without values
  -n, --values         print only values of the given variable(s)
  -p, --load[=<file>]  read values from file
  -f                   alias of -p
      --system         read values from all system directories
  -r, --pattern <expression>
                       select setting that match expression
  -q, --quiet          do not echo variable set
  -w, --write          enable writing a value to variable
  -o                   does nothing
  -x                   does nothing
  -d                   alias of -h

 -h, --help     display this help and exit
 -V, --version  output version information and exit

Reading

To fetch all the sysctl parameters:

sysctl -a

To only fetch the core kernel parameters:

sysctl -a | grep kernel

To get all values from the system directory:

sysctl -a --system

Changing parameters

There are two ways you can change a value:

1. Change it using sysctl command:
2. Change it by echoing the value into the /proc/sys directory.

sysctl -w kernel.hostname=newhostname

echo "newhostname" > /proc/sys/kernel/hostname

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References

• sysctl(8) - Linux manual page