Hello everyone In this Article we are going to learn How to manage demons and targets using systemctl command in Linux in a very simple and easy step-by-step approach
Daemons in Linux
The systemctl command is used to manage the demon and the targets that are running in the Linux kernel. The systemctl is a very useful command to start/stop/restart the particular demon that is running in the kernel.
Syntax Of systemctl command
systemctl option demon
1 How to check the status of service
To check the status for the service since how long that is running we can use the systemctl command with status as an option with the name of the service.
# systemctl status sshd
2. How to stop the service
To stop the service then we can write the stop option in with the service name.
# systemctl stop sshd
3 If we check status for sshd again now it is showing in stop stage
This is a temporary stop after reboot it will start again
# systemctl status sshd
When we reboot the server the service will run again
4 How to stop the service permanently
To stop the service permanent then we have to use the disable option in systemctl command this will disable the service after reboot also.
# systemctl disable sshd
5 How to start the service
To start the service again then we can add the start option with the service name systemctl command
But our service will stop again after reboot.
# systemctl start sshd
6 How to start the service permanently
To start the service permanently then we have to use enable the option in systemctl command and the service name
# systemctl enable sshd 
7 How to reload the service
To reload the service then we can use the reload option in systemctl command then it will reload the service.
Suppose that we have done a change in the configuration file then in order to tell the kernel for the change we need to reload the service.
# systemctl reload sshd
8 How to restart the service
To restart the service then we can add a restart option in systemclt command with the service name.
If we restart the service then our process id will change.
Suppose that 100 users are connected to our server and if we restart the service then the connection will break.
So we will reload the service instead of restarting the service.
For example when we do #systemctl status sshd we are having the PID of 6223
# systemctl restart sshd 
Now when we check status again then PID will changed to 7383
Type of targets in the Linux kernel –
There are 4 types of targets in the linux kernel
1 – Graphical.target -When we want to open GUI Mode then we have to be in this target
2 – multi-user.target – When we want to open CLI Mode then we have to be in this target
3 – rescue.target – When we want to troubleshoot the Operating system then we have to be in this target
4 – emegency.target – When we want to open emergency mode then we have to be in this target
We can set these targets as a permanent or a temporary in linux kernel These manage by systemctl
How to check the current target
To check the current target we can use systemctl command with the get-default option..
# systemctl get-default
How to convert to different targets
To convert to different targets, for example, rescue.target then we can use the isolate option and then target name.
# systemctl isolate rescue.target
But If we use the isolate option in the command then this will set temporary targets. After reboot, the target will be in default
How to set target permanently
To set the target permanently then we can use the set-default option in systemctl command with the target name.
# systemctl set-default multiuser.target 
Now if we want to go to graphical.target then we can execute .
# sysemctl set-default graphical.targetSimilarly if we want to go to rescue mode then we can execute.
# sysemctl set-default rescue.targetSimilarly if we want to go to emergency mode then we can execute
# systemctl isolate rescue.targetConclusion
If you want to learn Linux in the most simple language then please click on this link.
If you want to read online manual for systemctl command then click on this link
This is the complete knowledge of how we can manage the demons and targets using systemctl command the Linux kernel if you have any doubts please feel free to comment below. Please don’t forget to join our email subscription to get the latest updates on DevOps Articles
