updated notes

src/rhcsa.md

@@ -220,8 +220,8 @@ sudo crontab -e # Edit the cron table
 
 sudo crontab -l # List the cron table
 
-### crontab format
-```
+### crontab format ###
+
 * * * * * command # Run the command every minute
 
 0 12 * * * command # Run the command at 12:00 PM
@@ -229,6 +229,17 @@ sudo crontab -l # List the cron table
 0 0 * * * command # Run the command at 12:00 AM
 ```
 
+### at
+```bash
+at 12:00 PM # Schedule a command to run at 12:00 PM
+
+at -l # List all scheduled jobs
+
+atq # List all scheduled jobs
+
+atrm 1 # Remove the scheduled job with ID 1
+```
+