The most important commands, usable in most situations. See the detailed guides for specific commands/things to check.
- Physical/Network access layer
- Check the cables
- Check switch port LEDs
- Is de box connected to the correct switch?
- Internet layer:
- Check network settings:
ip a
ip r
(+ ping default gw)cat /etc/resolv.conf
(+dig www.google.com @a.b.c.d +short
)
- LAN connectivity:
- Ping between hosts, default GW
- Check DNS availability:
nslookup
,dig
,getent ahosts
- Check network settings:
- Transport layer
- Is the service running?
sudo systemctl status SERVICE.service
sudo systemctl start SERVICE.service
sudo systemctl enable SERVICE.service
- Does it use the correct ports/sockets?
sudo ss -tlnp
- Does the firewall allow traffic to those ports?
sudo firewall-cmd --list-all
sudo firewall-cmd --add-service=SERVICE --permanent
sudo firewall-cmd --add-port=PORT/tcp --permanent
sudo systemctl restart firewalld
- Is the service running?
- Application layer
- Check the logs:
sudo journalctl -f -u SERVICE.service
- Restart after each config file change:
sudo systemctl restart SERVICE.service
- Check the logs: