Mastering Network Command-Line Tools: A Practical Guide
Mastering Network Command-Line Tools: A Practical Guide
Introduction
Network troubleshooting and diagnostics are essential for system administrators, developers, and network enthusiasts. Understanding how to retrieve system information, query DNS records, analyze network connections, and inspect packet details is crucial. This blog will introduce various Linux network command-line tools based on practical experiments.
1. Get system and network information
hostname - Get system hostname
The hostname command is used to get the hostname of the system.
hostname
This command returns a unique name that identifies the computer on the network.
ip - Display network interface information
To get detailed network information, use:
ip address
This command displays the IP address assigned to each network interface. For example:
eth0: 148.60.12.8/24
Here, 148.60.12.8 is the IP address, and /24 represents the subnet mask 255.255.255.0.
2. Connectivity Testing
ping - Check Host Availability
To check if a host is online, use:
ping 148.60.12.7
If the host responds, it means the device is online; otherwise, it may be offline or blocked by a firewall.
nslookup - Query DNS Records
To query the DNS records for a domain, use:
nslookup 148.60.12.7
This tool helps resolve domain names and check their DNS configurations.
3. Querying System Databases
getent - Query System Databases
The getent command fetches entries from system databases such as /etc/passwd, /etc/group, /etc/hosts, and /etc/services. For example, to query commonly used services:
getent services https domain ftp smtp ssh
This command retrieves information about respective network services.
4. Checking Active Network Connections
ss - View Socket Statistics
The ss command provides detailed insights into network connections:
ss -tulpn
This displays active TCP/UDP connections and the processes using them.
5. Querying DNS Resolution Records
dig - Advanced DNS Query
To fetch detailed DNS information:
dig google.fr
This command returns DNS resolution data, including authoritative name servers.
6. Tracing Network Routes
traceroute - Track Packet Route
To trace the route packets take to reach a destination:
traceroute google.fr
This displays each hop along the route and is useful for diagnosing network latency or routing issues.
Conclusion
Mastering these command-line tools enhances network troubleshooting skills and enables efficient debugging. Whether checking DNS records, analyzing connections, or monitoring packet flow, these commands form the foundation of network diagnostics. Understanding their practical applications is essential for anyone working with networks.