Dig (domain information groper) is a tool that is used for querying DNS servers for various DNS records, making it very useful for troubleshooting DNS problems.
By the end of this guide you will know how to use dig to perform different types of DNS lookups in Linux.
The ‘ip’ command is used to print out various network information in Linux. It replaces the deprecated ‘ifconfig’ command, which is not even installed by default in CentOS 7.
The ip command is part of the iproute package, which is installed by default in most modern Linux distributions.
In the examples here you’ll see how to use the ip command to show network configuration such as link information, IP addresses and routing.
The GNU tape archive command, known as ‘tar’, is used to store many different files together into a single archive file. This makes it easy to perform backups and restores of files and directories in Unix/Linux based operating systems.
The practical examples in this guide will show you how to use the tar command in all sorts of different situations.
The ‘cat’ command is used to read and concatenate files, printing them out to standard output.
Cat comes from the GNU Coreutils package and should be available by default in Unix/Linux based operating systems.
The ‘ls’ command is a standard GNU command used in Unix/Linux based operating systems to list directory contents and display information about the sub directories and files within.
The practical examples in this guide will show you how to use the ls command in all sorts of different situations.
Wget is a non-interactive network downloader which can be used for downloading files in Unix/Linux. It supports the HTTP, HTTPS and FTP protocols and also has proxy support.
The wget command is quite powerful and has a lot of options available, in this guide we’ll be covering 20 of the most important wget examples that will help you learn how to best use it.
Swap space is an area of disk that is used to store memory to. Here we’ll take a look at managing swap space in Linux by determining what is actually using the swap space, controlling how frequently swap space is written to, and finally adding additional swap space if required.
Yellowdog Updater Modifier (yum) is an RPM based package manager which is used to install and update packages in various Linux distributions including CentOS, RHEL and Fedora.
Yum is quite powerful as it’s capable of automatically resolving dependency issues, and is similar to other package managers such as ‘apt-get’ in Debian based distributions.
These examples should serve as a useful introduction, guide or cheat sheet style resource for how to use the yum command in Linux.
The ‘history’ command available in Bash can be used to simply display your shell history, however there’s also a whole lot more that you can do with it, which we’ll demonstrate here.
Bash history allows us to quickly see what has been executed previously on a system, allowing you to hold users at least somewhat accountable for their actions (more on this later). It’s also useful if you’ve run something before and forgot the command, I can’t begin to tell you the number of times that I’ve done this!
Security Enhanced Linux (SELinux) is enabled and running in enforcing mode by default in CentOS/RHEL based Linux operating systems, and with good reason as it increases overall system security.
Despite this there may be times when you want to temporarily or permanently disable SELinux, which is what we’ll cover here.