Networking in Linux
Linux networking is fundamental to server administration. Linux powers most Internet infrastructure.
Network Configuration
ip addr (interfaces), ip route (routing). NetworkManager (nmcli, nmtui). netplan (Ubuntu), ifcfg (RHEL). /etc/resolv.conf (DNS), /etc/hosts (local mapping).
Firewall
iptables: chains (INPUT, OUTPUT, FORWARD), targets (ACCEPT, DROP). firewalld (RHEL): zone-based. ufw (Ubuntu): simplified. Filter by port, protocol, IP, connection state.
SSH
Encrypted remote access. ssh user@host. Key-based auth: ssh-keygen, ssh-copy-id. Disable password auth for security. scp for file copies. SSH config simplifies connections.
DNS
dig, nslookup query DNS. BIND server. Configure zones, records (A, AAAA, CNAME, MX, NS). DNS caching improves performance.
Network Services
Apache/Nginx (web), Postfix (mail), dhcpd (DHCP), NFS (file sharing), Samba (Windows sharing). Managed with systemctl.
Troubleshooting
ping (connectivity), traceroute (path), ss/netstat (ports), tcpdump (packets), nmap (scan), curl/wget (HTTP). Check physical → IP → DNS → application layer.
Summary
Linux networking: configuration, firewalls, SSH, DNS, services, and troubleshooting are essential for server management.