init: add page (#14039)

pages/linux/init.md

@@ -0,0 +1,25 @@
+# init
+
+> Linux run level manager.
+> Requires the SYSVINIT compile-time option to be enabled if using systemd.
+> More information: <https://manned.org/man/init.8>.
+
+- Set the system to run a graphical environment:
+
+`sudo init 5`
+
+- Set the system to run multiuser terminal:
+
+`sudo init 3`
+
+- Shut down the system:
+
+`init 0`
+
+- Reboot the system:
+
+`init 6`
+
+- Set the system to run on terminal with only root user allowed and no networking:
+
+`sudo init 1`