# 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
```