What Are Services And Daemons In Linux?

Daemons:

They are the processes which run in the background and are not interactive. They have no controlling terminal. They perform certain actions at predefined times or in response to certain events. In Linux, the names of daemons end in d. Some examples include httpd, nfsd, sshd,named and lpd. Daemons usually perform critical system tasks such as control swap-space, memory management and various other tasks. Service run on Windows, Daemons run on Linux. In short, system service in Linux are called Daemons.

Introduction to Systemd:

Systemd is a system and service manager for Linux-based operating system for managing services. Systemd as a default “service management tool. Systemd uses “units”, which can be services (.service), mount point (.mount, device(.device), or socket (.socket). The systemctl command manages all these types of unis. In short, Systemd is a suie of tools that provides system and services management for the Linux operating system

Introduction to Systemctl:

system and service manager. To manage services on a systemd enabled for controlling the systemd the systemctl command. To manage services on a systemd enabled server, our main tool is the systemctl command. To view, start, stop, restart, enable, or disable system services daemons, use the systemctl command

Display systemctl version [root@asim ~]# systemctl –version

Check the installed binaries and libraries [root@asim ~]# whereis systemctl

To start service [root@asim ~]# systemctl start httpd.service Or [root@asim ~]# systemctl start httpd

Reload the services [root@asim ~]# systemctl reload httpd

To restart the service [root@asim ~]# systemctl restart httpd

Check the status of a service [root@asim ~]# systemctl status httpd

Enable service to start on boot [root@asim ~]# systemctl enable httpd

Disabled service to not to start  on boot [root@asim ~]# systemctl disabled httpd

Check if service active or not [root@asim ~]# systemctl is-active httpd

Check if service enabled or not [root@asim ~]# systemctl is-enabled httpd

Display a list of properties [root@asim ~]# systemctl show httpd

Making it impossible to start [root@asim ~]# systemctl mask httpd

Making it possible to start [root@asim ~]# systemctl umask httpd

kill a service [root@asim ~]# systemctl kill httpd

Check all the services running [root@asim ~]# systemctl –t service