finished debugging services

docs/linux/debugging-services.md

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+# Debugging Services
+
+The below are a bunch of commands that can be used to debug services on a Linux system (e.g. Java App / .NET App and so on)
+
+#### Finding the process
+
+```bash
+# Generic
+ps aux | grep <process_name>
+
+# Java
+ps aux | grep java
+```
+
+#### Find the service if a systemd service is running
+
+```bash
+# Generic
+sudo systemctl status <service_name>
+
+# Specific service
+sudo systemctl status myapp
+
+# Find service
+sudo systemctl list-units --type=service | grep <service_name>
+```
+
+#### View logs for a systemd service
+
+```bash
+# Generic
+sudo journalctl -u <service_name> -n 100 --no-pager
+
+# Specific service
+sudo journalctl -u myapp -n 100 --no-pager
+```
+
+#### Check port for a service
+
+```bash
+# Generic
+sudo ss -tulpn | grep <port_number>
+
+# Specific port
+sudo ss -tulpn | grep 8080
+```
+
+#### Search for OOM (Out of Memory) errors in logs
+
+```bash
+# Generic
+sudo journalctl -k | grep -i "out of memory|kill|oom" | tail -n 100
+sudo dmesg | grep -i "out of memory|kill|oom" | tail -n 100
+```
+
+#### System resource usage
+
+```bash
+# Display memory usage
+free -h
+
+# Disc usage
+df -h
+
+# Usage on a specific directory
+du -sh /path/to/directory | sort -rh
+
+# CPU
+top
+htop
+```