Essential Linux Network Commands: A Practical Guide

 1# Show network interfaces
 2ip addr show
 3
 4# Enable/disable interface
 5ip link set eth0 up
 6ip link set eth0 down
 7
 8# Set IP address
 9ip addr add 192.168.1.100/24 dev eth0
10
11# Show routing table
12ip route show
13
14# Add static route
15ip route add 10.0.0.0/24 via 192.168.1.1

 1# Show TCP connections
 2ss -ta
 3
 4# Show listening ports
 5ss -ltpn
 6
 7# Display processes using port
 8ss -ltpn | grep :80
 9
10# Show UDP sockets
11ss -ua

 1# Check NetworkManager status
 2systemctl status NetworkManager
 3
 4# View all devices
 5nmcli device status
 6
 7# Show connection details
 8nmcli connection show
 9
10# View real-time logs
11journalctl -fu NetworkManager
12
13# Restart NetworkManager
14sudo systemctl restart NetworkManager
15
16# Connect specific interface
17nmcli device connect eth0

 1# Basic ping
 2ping google.com
 3
 4# Limit to 5 packets
 5ping -c 5 192.168.1.1
 6
 7# Set interval (seconds)
 8ping -i 0.5 8.8.8.8
 9
10# Set packet size
11ping -s 1500 google.com

1# Basic trace
2traceroute google.com
3
4# Use TCP
5traceroute -T google.com
6
7# Specify port
8traceroute -p 443 google.com

 1# Scan host
 2nmap 192.168.1.100
 3
 4# Scan network range
 5nmap 192.168.1.0/24
 6
 7# Scan specific ports
 8nmap -p 80,443 192.168.1.100
 9
10# OS detection
11nmap -O 192.168.1.100

 1# GET request
 2curl http://example.com
 3
 4# Download file
 5curl -O http://example.com/file.zip
 6
 7# POST request
 8curl -X POST -d "data=value" http://api.example.com
 9
10# Show headers
11curl -I https://example.com

 1# Basic lookup
 2dig example.com
 3
 4# Query MX records
 5dig example.com MX
 6
 7# Use specific DNS server
 8dig @8.8.8.8 example.com
 9
10# Trace resolution
11dig +trace example.com

 1# Capture interface packets
 2tcpdump -i eth0
 3
 4# Capture specific port
 5tcpdump -i eth0 port 80
 6
 7# Save to file
 8tcpdump -w capture.pcap
 9
10# Read from file
11tcpdump -r capture.pcap

1# List rules
2iptables -L
3
4# Allow SSH
5iptables -A INPUT -p tcp --dport 22 -j ACCEPT
6
7# Block IP
8iptables -A INPUT -s 192.168.1.100 -j DROP

1# Listen on port
2nc -l 8080
3
4# Connect to port
5nc example.com 80
6
7# Port scanning
8nc -zv example.com 20-30

1# Basic lookup
2host example.com
3
4# Reverse lookup
5host 8.8.8.8
6
7# Query MX records
8host -t MX example.com

 1# Check if web server is listening
 2ss -ltpn | grep :80
 3
 4# Test local web server
 5curl -I http://localhost
 6
 7# Check server certificate
 8openssl s_client -connect yourdomain.com:443
 9
10# Monitor HTTP traffic
11tcpdump -i eth0 port 80 -A
12
13# Check error logs
14tail -f /var/log/httpd/error_log

 1# Test DNS and internet connectivity
 2ping -c 3 8.8.8.8
 3ping -c 3 google.com
 4
 5# Check interface status and IP
 6ip addr show
 7nmcli device status
 8
 9# Verify routing
10ip route show
11traceroute problematic-server.com
12
13# Monitor interface traffic
14tcpdump -i eth0 -n
15
16# Check DNS resolution
17dig +trace yourdomain.com

 1# Port scanning
 2nmap -sS -p- 192.168.1.0/24
 3
 4# Check open connections
 5ss -tapn
 6
 7# Monitor connections in real-time
 8watch ss -tapn
 9
10# Review firewall rules
11firewall-cmd --list-all
12iptables -L -n -v
13
14# Check SELinux status
15sestatus
16getenforce

 1# Network interface statistics
 2ip -s link show
 3
 4# Monitor bandwidth by process
 5iftop -i eth0
 6
 7# Track network latency
 8mtr google.com
 9
10# Check network load
11netstat -s
12
13# Monitor network errors
14watch -n1 'netstat -i'
15
16# NetworkManager real-time logs
17journalctl -fu NetworkManager

 1# Check system services
 2systemctl status NetworkManager
 3systemctl status firewalld
 4
 5# View network services
 6ss -tulpn
 7
 8# DNS resolution check
 9cat /etc/resolv.conf
10dig google.com
11
12# Review network logs
13journalctl -u NetworkManager