Add service management content (#1588)

content/roadmaps/102-devops/content/101-os-concepts/109-service-management.md

@@ -1 +1,10 @@
-# Service management
+# Service Management (systemd)
+
+`systemd` is a **System** Management **D**aemon which replaces the sysvinit process to become the first process with PID = 1, which gets executed in user space during the Linux start-up process. It is a system that is designed specifically for the Linux kernel. It is now being used as a **replacement of init.d** to overcome shortcomings of it. It uses `systemctl` command to perform related operations.
+
+e.g. `$ systemctl start [service-name]`, `$ systemctl poweroff`
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.geeksforgeeks.org/linux-systemd-and-its-components/'>What is systemd? and its commands</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://uace.github.io/learning/init-vs-systemd-what-is-an-init-daemon'>init.d vs systemd</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.tecmint.com/systemd-replaces-init-in-linux/'>Why Systemd as a replacement of init.d?</BadgeLink>