# Logs & Network Troubleshooting — Linux Command Line Fundamentals

Source: https://www.geekswithgeeks.com/en/linux/linux-logs-network

> Read system logs with journalctl and /var/log, and inspect addresses and listening ports with ip and ss.

## Reading logs

On systemd distros `journalctl` reads the journal; classic text logs live in `/var/log`.

```bash
journalctl -u nginx --since "1 hour ago"
journalctl -p err -b           # errors since boot
tail -f /var/log/syslog
```

## Network tools

`ip` shows interfaces and routes; `ss` shows sockets and the processes listening on ports.

```bash
ip addr show
ip route
ss -tulpn          # listening TCP/UDP ports with processes
curl -I https://example.com
```

When a service fails, check `systemctl status`, then its journal, then the port with `ss`. Work from the service outward.