Different Run Levels in Linux
Different Run Levels in Linux: Unix-based operating systems are implemented
with a predefined set of runlevels that presented specific mode of operation.
These runlevels are numbered from 0 to 6 and were defined by the system
administrator to enabling the runlevels.
Where as runlevels are replaced with systemd
targets in RHEL7. Systemd targets are represented by target units.
Target units end with the .target file extension.
Also follow other topics for Comparison of the service utility with systemctl – RHEL-7 and How to Enable or Disable services on boot with chkconfig | systemctl – RHEL-6/7/8
Different Run Levels in Linux: RHEL-6
Runlevel
|
Mode
|
Action
|
0
|
Halt
|
Shuts down system
|
1
|
Single-User Mode
|
Does not configure network interfaces, start daemons, or allow
non-root logins
|
2
|
Multi-User Mode
|
Does not configure network interfaces or start daemons.
|
3
|
Multi-User Mode with Networking
|
Starts the system normally.
|
4
|
Undefined
|
Not used/User-definable
|
5
|
X11
|
As runlevel 3 + display manager(X)
|
6
|
Reboot
|
Reboots the system
|
Default runlevel in linux (RHEL-6) are Runlevel-3 (Multi-User
Mode with Networking) and Runlevel-5 (X11). All Runlevel are the script can be
found in rc sub directories. At /etc/rc.d directory
there will be either a set of files named rc.0,
rc.1, rc.2, rc.3, rc.4, rc.5 and rc.6, or a set of directories
named rc0.d, rc1.d, rc2.d, rc3.d, rc4.d, rc5.d
and rc6.d.
Runlevel command used to find current and previous runlevels.
# runlevel
N 5
# who -r
run-level 5
2019-09-12 13:48
Different Run Levels in Linux: RHEL-7
Runlevel
|
Target
Units
|
Description
|
0
|
runlevel0.target, poweroff.target
|
Shut down and power
off the system
|
1
|
runlevel1.target, rescue.target
|
Set up a rescue shell
|
2
|
runlevel2.target, multi-user.target
|
Set up a non-graphical
multi-user system
|
3
|
runlevel3.target, multi-user.target
|
Set up a non-graphical
multi-user system
|
4
|
runlevel4.target, multi-user.target
|
Set up a non-graphical
multi-user system
|
5
|
runlevel5.target, graphical.target
|
Set up a graphical
multi-user system
|
6
|
runlevel6.target, reboot.target
|
Shut down and reboot
the system
|
Linux runlevel command as below how to check
runlevel in linux.
Runlevel command used to find current and previous runlevels.
# runlevel
N 5
Another way to find current and previous runlevels using
who command with -r parameter.
# who -r
run-level 5
2019-09-12 13:48
Also follow other topics for Comparison
of the service utility with systemctl – RHEL-7 and How to Enable
or Disable services on boot with chkconfig | systemctl – RHEL-6/7/8
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