Diagnostics and Testing

9 Guides Available

Troubleshooting Network Issues - IPv4 and IPv6

A successful internet circuit from host-to-host usually involves many components: from an application in one host, to an application in the desired target host. This tutorial covers troubleshooting connectivity between apps, and their hosts, whether over IPv4, IPv6, or an IPv6 tunnel over IPv4.

Checking Open and Listening Ports on Linux Using netstat and ss

One step in securing a Linux computer system is identifying which ports are active. Your system’s active ports give you information about which outside applications may be connected to your system. You can also discover if you are unintentionally exposing an application or service to the internet, like a MySQL database. There are several Linux tools that help you discover which ports are in use and identify both ends of active communications. This guide introduces three common tools you can use with links to guides that dive deeper into each tool.

Inspecting Network Information with netstat

The netstat command line utility shows information about the network status of a workstation or server. netstat is available on Unix-like and Windows operating systems, with some differences in its usage between these systems.

Learning to Use netcat to its Full Potential

Netcat is a simple but handy UNIX utility that reads and writes data across network connections, using either TCP or UDP. The purpose of this guide is to help you learn the netcat command line utility and use it productively.

Learning to Use the ss Tool to its Full Potential

Introduction

The study of socket connections is important for every UNIX and network administrator because it allows you to better understand your Linux system’s status. Written by Alexey Kuznetosv to replace the famous netstat utility , the more capable ss (socket statistics) utility allows you to monitor TCP, UDP, and UNIX sockets. The purpose of this guide is to help you learn the ss utility and to use it as productively as possible.

How to List Open Files with lsof

Introduction

lsof was created by Victor A. Abell and is a utility that lists open files. Everything in Linux can be considered a file. This means that lsof can gather information on the majority of activity on your Linode, including network interfaces and network connections. lsof by default outputs a list of all open files and the processes that opened them.