updated notes

src/rhcsa.md

@@ -240,7 +240,52 @@ atq # List all scheduled jobs
 atrm 1 # Remove the scheduled job with ID 1
 ```
 
+### systemd
 
+```bash
+sudo systemctl start sshd # Start the sshd service
+sudo systemctl stop sshd # Stop the sshd service
+sudo systemctl restart sshd # Restart the sshd service
+
+sudo systemctl enable sshd # Enable the sshd service to start on boot
+sudo systemctl disable sshd # Disable the sshd service from starting on boot
+sudo systemctl status sshd # Check the status of the sshd service
+
+sudo systemctl daemon-reload # Reload the systemd daemon
+
+sudo systemctl mask sshd # Mask the sshd service
+sudo systemctl unmask sshd # Unmask the sshd service
+```
+
+### systemd service and timer commands
+
+```bash
+### Creating a service ###
+sudo nano /etc/systemd/system/myapp.service
+# [Unit]
+# Description=My App
+# After=network.target
+
+# [Service]
+# ExecStart=/usr/bin/myapp
+
+
+### Creating a timer ###
+sudo nano /etc/systemd/system/myapp.timer
+# [Unit]
+# Description=My App Timer
+# After=myapp.service
+
+# [Timer]
+# OnBootSec=10min
+# OnCalendar=daily
+
+### Tying the timer to the service ###
+sudo systemctl link /etc/systemd/system/myapp.timer 
+
+### Starting a service ###
+sudo systemctl start myapp
+```