Network command in Linux
| Command |
Description |
| ifconfig |
Display network interface configuration. |
| ip addr |
Show IP addresses and network interfaces. |
| ip route |
Display the routing table. |
| ping |
Test network connectivity to a host. |
| traceroute |
Trace the route packets take to a host. |
| netstat |
Show network statistics and connections. |
| ss |
Similar to netstat, show socket statistics. |
| nslookup |
Query DNS for specific domain information. |
| dig |
DNS lookup utility for querying DNS servers. |
| host |
DNS lookup utility for querying DNS servers. |
| wget |
Download files from the internet. |
| curl |
Transfer data with URLs using various protocols. |
| ssh |
Securely connect to a remote server. |
| telnet |
Connect to a remote host using Telnet protocol. |
| ifup / ifdown |
Bring up or down a network interface. |
| route |
Show or modify the IP routing table. |
| iptables |
Configure firewall rules. |
| nmap |
Network scanner for discovering open ports. |
Network FAQ in Linux
| Question |
Answer |
| How can I check my network interface name? |
Use the ifconfig or ip addr command to list all network interfaces. The interface names appear as eth0, enp2s0, etc. |
| How do I check my IP address? |
Run ip addr or ifconfig to display the IP addresses associated with each network interface. |
| What command can I use to check network connectivity to a host? |
Use ping to test if a host is reachable over the network. Example: ping google.com |
| How can I find the route packets take to a host? |
Use traceroute or traceroute6 to trace the path packets take to reach a host. Example: traceroute google.com |
| How do I check the network connection status and active connections? |
Use netstat or ss command to view network connections and statistics. Example: netstat -tuln |
| How can I diagnose DNS issues? |
Use nslookup, dig, or host to query DNS servers and troubleshoot DNS resolution problems. |
| How do I configure firewall rules? |
You can use iptables or ufw (Uncomplicated Firewall) to set up and manage firewall rules. |
| How can I check the status of network services? |
Use systemctl to check the status of network-related services like networking, NetworkManager, etc. |
| How do I test a remote server’s port availability? |
Use telnet or nc (netcat) to check if a specific port on a remote server is open. Example: telnet example.com 80 |
| How can I check network link status and statistics? |
Use ethtool to display network interface link status, speed, and statistics. Example: ethtool eth0 |
| Question |
Answer |
| How do I change my IP address in Linux? |
You can use the ifconfig or ip command to change the IP address of a network interface. Example: sudo ifconfig eth0 192.168.1.100 |
| How can I set a static IP address in Linux? |
Edit the network configuration file (e.g., /etc/network/interfaces or /etc/sysconfig/network-scripts/ifcfg-eth0). Example: Edit /etc/sysconfig/network-scripts/ifcfg-eth0: NAME=eth0 |
| How do I change the hostname of my Linux system? |
Edit the /etc/hostname file and update the hostname, then reboot the system or use hostnamectl command. Example: sudo nano /etc/hostname Example: Update with desired hostname Example: sudo hostnamectl set-hostname newhostname |
| How can I configure a network bridge in Linux? |
Use tools like brctl or nmcli to create and manage network bridges for virtual machines or containers. Example: sudo nmcli connection add type bridge con-name br0 ifname br0 |
| How do I change the DNS server in Linux? |
Update the /etc/resolv.conf file with the desired DNS server IP addresses or use nmcli to manage network connections. Example: sudo nano /etc/resolv.conf Example: Add nameserver 8.8.8.8 |
| How can I change the default gateway in Linux? |
Use the ip command or edit the network configuration file to change the default gateway IP address. Example: sudo ip route add default via 192.168.1.1 |
| How do I set up a virtual network interface in Linux? |
Use the ifconfig or ip command to create a virtual network interface with the :X notation (e.g., eth0:1). Example: sudo ifconfig eth0:1 192.168.1.101 netmask 255.255.255.0 |
| How can I change the MTU size in Linux? |
Use the ip command to set the MTU size of a network interface. Example: sudo ip link set eth0 mtu 1500 |
| How do I configure a proxy server in Linux? |
Edit the system-wide environment variables or configure proxy settings for specific applications like apt or curl. Example: Set HTTP_PROXY and HTTPS_PROXY environment variables or edit /etc/apt/apt.conf |
| How can I enable or disable IPv6 in Linux? |
Use sysctl to enable or disable IPv6 support in the kernel. Example: sudo sysctl net.ipv6.conf.all.disable_ipv6=1 Example: sudo sysctl net.ipv6.conf.all.disable_ipv6=0 |
Network configuration file in Linux
| Configuration |
Description |
| /etc/network/interfaces |
This file is used for network interface configuration on Debian-based systems (e.g., Ubuntu). |
/etc/sysconfig
/network-scripts/ifcfg-eth0 |
Configuration file for network interface eth0 on Red Hat-based systems (e.g., CentOS, Fedora). |
| /etc/netplan/*.yaml |
YAML files used for network configuration on modern Ubuntu systems with Netplan. |
| /etc/resolv.conf |
Contains DNS (Domain Name System) configuration, specifying name servers to resolve domain names. |
| /etc/hostname |
This file stores the hostname of the system. |
| /etc/hosts |
Maps IP addresses to hostnames, used for local hostname resolution. |
| /etc/nsswitch.conf |
Configuration file that determines the order of resolution for various services (e.g., hosts, DNS). |
/etc/NetworkManager
/NetworkManager.conf |
Configuration file for NetworkManager, a daemon managing network connectivity on many Linux systems. |
| /etc/sysctl.conf |
Contains kernel parameters that can be adjusted to optimize network performance and behavior. |
Troubleshoot network issues in Linux
| Step |
Description |
| Check Physical Connection |
Ensure that all network cables are properly connected, and the network interface (e.g., Ethernet adapter) is recognized by the system. |
| Check Network Interface |
Use ifconfig or ip addr to verify the network interface’s status and IP address assignment. |
| Check Network Configuration |
Review the network configuration files (e.g., /etc/network/interfaces, /etc/sysconfig/network-scripts/ifcfg-eth0) for correctness. |
| Check DNS Configuration |
Verify the DNS settings in /etc/resolv.conf and ensure DNS servers are reachable. |
| Check Default Gateway |
Use ip route or netstat -r to check the default gateway and verify that it is reachable. |
| Check Network Services |
Confirm that necessary network services (e.g., NetworkManager, dhclient, systemd-networkd) are running and configured properly. |
| Test Network Connectivity |
Use ping to test connectivity to local and remote hosts. |
| Trace Route |
Use traceroute or traceroute6 to identify the route packets take to reach a specific host or diagnose network latency. |
| Check Firewall Rules |
Inspect firewall configurations (iptables, ufw) to ensure they aren’t blocking necessary network traffic. |
| Check Network Tools |
Use tools like netstat, ss, ip, ethtool, tcpdump, or wireshark to analyze network traffic and identify anomalies. |
These steps provide a systematic approach to troubleshooting common network issues in Linux. By following these procedures, you can identify and resolve problems related to network connectivity, configuration, and services effectively.