updated notes

src/rhcsa.md

@@ -839,3 +839,51 @@ logger -p local0.info "This is a test message" # Log a message to the local0.inf
 
 sudo tail /var/log/messages # Display the messages
 ```
+
+## Troubleshoot RHEL Systems
+
+### Troubleshooting Capacity Problems
+```bash
+### df
+sudo df -h # Display the disk space usage
+sudo df -i # Display the inode usage
+sudo df -T # Display the filesystem type
+
+### dd
+sudo dd if=/dev/zero of=/dev/sda1 bs=1M count=100 # Create a 100MB file on the /dev/sda1 partition
+sudo dd if=/dev/zero of=/dev/sda1 bs=1M count=100 status=progress # Create a 100MB file on the /dev/sda1 partition with progress
+
+### du
+sudo du -hs /home/user1 # Display the disk space usage of the /home/user1 directory
+sudo du -h file.txt # Display the disk space usage of the file.txt file
+```
+
+### Troubleshooting CPU Issues
+```bash
+### uptime
+sudo uptime # Display the uptime of the system
+
+### lscpu
+sudo lscpu # Display the CPU information
+
+### stress test cpu with stress-ng
+sudo stress-ng --cpu 2 --timeout 10s # Stress test the CPU for 10 seconds
+
+### vmstat
+sudo vmstat 1 5 # Display the VM statistics every 1 second for 5 seconds
+
+### top
+sudo top # Display the top processes
+```
+
+### Troubleshooting Memory Issues
+```bash
+### free
+sudo free -h # Display the memory usage
+
+### vmstat
+sudo vmstat 1 5 # Display the VM statistics every 1 second for 5 seconds
+
+### top
+sudo top # Display the top processes then press m to sort by memory
+```