Linodes run Linux. Linux is an operating system, just like Windows and Mac OS X. As an operating system, Linux manages your Linode's hardware and provides services your other software needs to run.
Linux is a very hands-on operating system. If running Windows is like driving an automatic, then running Linux is like driving a stick. It can take some work, but once you know your way around Linux, you'll be using the command line and installing packages like a pro. This article aims to ease you into the world of Linux.
This guide is intended to be very beginner-friendly. It takes a Linux 101 approach to explanations for basic concepts. There are a few how-to sections as well, which are intended to get you on your feet with your Linode. At times we'll link off to a different guide that has more details on a particular topic.
Everything on a Linux system is case-sensitive. That means that photo.jpg, photo.JPG, and Photo.jpg are all different files. Usernames and passwords are also case-sensitive.
This section provides a brief overview of the history of Linux.
Linux, like Mac OS X, is based on the Unix operating system. A research team at AT&T's Bell Labs developed Unix in the late 1960s and early 1970s with a focus on creating an operating system that would be accessible and secure for multiple users.
Corporations started licensing Unix in the 1980s and 1990s. By the late 1980s, there was interest in building a free operating system that would be similar to Unix, but that could be tinkered with and redistributed. In 1991, Linus Torvalds released the Linux kernel as free, open-source software. Open source means that the code is fully visible, and can be modified and redistributed.
Strictly speaking, Linux is the kernel, not the entire operating system. The kernel provides an interface between your Linode's hardware and the input/output requests from applications. The rest of the operating system usually includes many GNU libraries, utilities, and other software, from the Free Software Foundation. The operating system as a whole is known as GNU/Linux.
Let's begin at the beginning. If some of this is a repeat for you, feel free to skip ahead!
Your Linode is a type of server. What's a server? A server is a type of computer that provides services over a network, or connected group of computers. When people think about servers, they're usually thinking of a computer that is:
Since a server is a type of computer, there are a lot of similarities between a Linode and your home computer. Some important similarities include:
Ready to get started? The first step is to install Linux.
Here at Linode, you install Linux using the Linode Manager dashboard. By clicking a few buttons on our dashboard, you effectively accomplish the same thing as popping a Windows or Mac OS X installation CD into your computer.
Before we get to installing your Linux operating system, there's one more concept to introduce. Linux comes in quite a few different versions, known as distributions. It's a bit like Windows XP vs. Windows 8, except that the different Linux distributions aren't just upgraded versions of each other - they're different up-to-date (and out-of-date) flavors of Linux. Different distributions install different default bundles of software. The differences between the Linux distributions aren't super important for a beginning user, so we won't get into them here; feel free to jump to the Distributions section at the end of this article or read more on your own if you're interested. For now, if you don't have a particular distribution in mind, we recommend installing Ubuntu 12.04 LTS. This distribution is good for Linux beginners, because it has a lot of support available and doesn't change too often.
Now you're ready to install Linux. We walk you through this process in the Getting Started article. Start at the beginning. When you get to the part where you need to choose your distribution from the dropdown menu, choose Ubuntu 12.04 LTS. Work your way through the article until you finish the Booting Your Linode section.
Now that Linux is installed, it's time to start learning how to use it! The best way to learn the Linux operating system is to dive in and start doing things. Before you can interact with your Linode, you have to connect to it, so that's the next step.
Since your Linode is physically housed in either the Tokyo, London, Newark, Atlanta, Dallas, or Fremont data center, you can't just plug in a keyboard, monitor, and mouse to interact with it. You have to use the Internet and a special tool called a terminal. A terminal runs a shell, which lets you use text commands to interact with your server, a lot like the old DOS prompts in Windows. The Secure Shell (SSH) protocol lets you send these commands to your Linode over a secure Internet connection from your local workstation.
In this guide, we'll mostly be using the terms terminal, shell, and SSH to refer to the interface you use to send text commands to your Linux system. These are different tools that layer on top of each other to let you interact with your server. To learn more, read these simplified definitions:
It's time to follow the next section of the Getting Started article, Connecting to Your Linode. You can follow along with the written instructions or watch the videos, or both. It will help you install a terminal emulator, then use it to establish an SSH connection to your Linode.
Once you connect to your Linode, you should be looking at a shell prompt like this and a blinking cursor:
What does this bit of text mean? The entire thing is the shell prompt. It's your terminal's way of telling you that it's ready for you to enter the next command. The different parts of the shell prompt also have meanings.
You can type any valid Linux shell command at the blinking cursor after the shell prompt. We'll go over a few practical commands in the rest of this article, but to get a really good in-depth introduction to the command-line interface, you should read the Using the Terminal article as well.
These command line tips will make your Linux forays much more effective:
In this section, we'll look at the structure of a Linux server. Everything on your Linode is a file or a directory. Remember, directory is the Linux term for a folder. Let's find out where you are in the directory structure. Make sure your terminal application is selected and that you're still logged in to your Linode. You should see a blinking cursor where you can start typing. For your first command, let's use the pwd command. Short for print working directory, its output lets you view the full path to your current directory. Type the following command after the shell prompt (just the pwd part):
Press Return to execute the command. You should see the following output:
The output of pwd shows you the full path to your current directory or directory. At the moment, you're inside the /root directory. You will always be inside a particular directory when you execute shell commands, although which directory you're in can change. The pwd command is very useful because it shows you exactly where you are in your Linode's directory structure.
Linux uses a tree of nested directories to keep its files organized. The highest-level directory is called the root directory. It's designated with a single slash. Let's move into the root directory, /, with another command. The cd command is short for change directory. After the cd part comes a space and then the file path. The file path can be long or short, depending on how deep you're going into the directory structure. To get to the root directory, type the following command, and press Return to execute it. The shell prompt (root@localhost:~#) will still be displayed on your screen, but this time we'll show you just the command:
Unlike in Windows, there are no different disks or drives; the root directory is the highest-level directory for all Linux systems. The root directory is a bit like the filing cabinet for your server. Underneath the root directory are more directories. Directories can go inside other directories, as illustrated below:
For example, most Linux systems have directories called lib and var (along with several others) underneath the root directory. The lib directory contains system libraries, while the var directory contains all of the files on your system that are likely to change, such as your logs and your mail messages.
The list command, ls, shows everything that's directly inside of your current directory. To make the output the most helpful, we'll add a few flags to the ls command as well; in this case, the -ahl part of the command. Type the following command, and press Return to execute it:
You should see output that looks something like this:
total 84K drwxr-xr-x 22 root root 4.0K Apr 30 2012 . drwxr-xr-x 22 root root 4.0K Apr 30 2012 .. drwxr-xr-x 2 root root 4.0K Nov 6 16:04 bin drwxr-xr-x 3 root root 4.0K Feb 4 2013 boot drwxr-xr-x 11 root root 14K Nov 6 16:17 dev drwxr-xr-x 94 root root 4.0K Dec 10 20:27 etc drwxr-xr-x 4 root root 4.0K Feb 19 2013 home drwxr-xr-x 16 root root 4.0K Nov 6 16:04 lib drwx------ 2 root root 16K Apr 26 2012 lost+found drwxr-xr-x 3 root root 4.0K Apr 26 2012 media drwxr-xr-x 2 root root 4.0K Apr 19 2012 mnt drwxr-xr-x 3 root root 4.0K Nov 18 13:34 opt dr-xr-xr-x 141 root root 0 Nov 6 16:16 proc drwx------ 3 root root 4.0K Apr 7 2013 root drwxr-xr-x 15 root root 560 Dec 10 15:57 run drwxr-xr-x 2 root root 4.0K Nov 6 16:04 sbin drwxr-xr-x 2 root root 4.0K Mar 5 2012 selinux drwxr-xr-x 2 root root 4.0K Apr 26 2012 srv dr-xr-xr-x 13 root root 0 Nov 6 16:16 sys drwxrwxrwt 2 root root 4.0K Dec 10 21:09 tmp drwxr-xr-x 10 root root 4.0K Apr 26 2012 usr drwxr-xr-x 13 root root 4.0K Nov 6 16:04 var
That's quite a bit of output. The most important part is the list of directory and file names, all the way over on the right. They're listed alphabetically. You'll notice the directories lib and var from the image, as well as several others.
The /root directory is not the same as the / directory. / is the top-level directory of the server. Everything else is inside it. It is called the root directory when you're talking about it, but its name on the server is just /. On the other hand, the /root directory is the home directory for the root user. It's a sub-directory under the / directory, and it's where the root user starts after logging in to a new SSH session.
If you open the var directory, you'll find more directories, such as log for your logs, and mail for your system mail. Move into the var directory by executing the cd command:
View the contents of the var directory with the ls command, just like we did earlier:
You'll see another list of directories:
total 52K drwxr-xr-x 13 root root 4.0K Nov 6 16:04 . drwxr-xr-x 22 root root 4.0K Apr 30 2012 .. drwxr-xr-x 2 root root 4.0K Nov 19 06:27 backups drwxr-xr-x 9 root root 4.0K Apr 6 2013 cache drwxrwsrwt 2 root whoopsie 4.0K Apr 26 2012 crash drwxr-xr-x 37 root root 4.0K May 29 2013 lib drwxrwsr-x 2 root staff 4.0K Apr 19 2012 local lrwxrwxrwx 1 root root 9 Apr 30 2012 lock -> /run/lock drwxr-xr-x 14 root root 4.0K Dec 12 06:53 log drwxrwsr-x 2 root mail 4.0K Aug 8 03:50 mail drwxr-xr-x 2 root root 4.0K Apr 26 2012 opt lrwxrwxrwx 1 root root 4 Nov 6 16:04 run -> /run drwxr-xr-x 6 root root 4.0K May 29 2013 spool drwxrwxrwt 2 root root 4.0K Feb 4 2013 tmp drwxr-xr-x 2 root root 4.0K Apr 6 2013 www
Here you can see the log and mail directories that we discussed, as well as several others. At the top of the list, you'll see two little directories named . and .. with periods. Similar to the tilde (~) we saw earlier, these directories are actually shortcuts or aliases, that appear in every directory. The single-period directory indicates the current directory. The double-period directory indicates the directory above the current one. So, if you are inside a lower-level directory and want to move up again, just use the cd .. command. To move back up to /, type the following command:
You should be in the / directory again. You can use pwd to verify this.
Finally, let's take a look at the lib directory. First, move into lib with the cd command:
List its contents with the ls command:
Inside, you'll see more directories and long list of library files that all start with lib. The output is very long, so we're just showing part of it here. The ... indicates that the output continues.
total 1.2M drwxr-xr-x 16 root root 4.0K Nov 6 16:04 . drwxr-xr-x 22 root root 4.0K Apr 30 2012 .. lrwxrwxrwx 1 root root 21 Apr 6 2013 cpp -> /etc/alternatives/cpp drwxr-xr-x 2 root root 4.0K Apr 26 2012 firmware drwxr-xr-x 2 root root 4.0K Feb 4 2013 hdparm drwxr-xr-x 3 root root 8.0K Oct 23 00:28 i386-linux-gnu drwxr-xr-x 2 root root 4.0K Mar 18 2013 init -rwxr-xr-x 1 root root 74K Mar 30 2012 klibc-LZ1cv1NoEVO2ugnvqTw3e4qPc8Y.so lrwxrwxrwx 1 root root 25 Sep 30 14:38 ld-linux.so.2 -> i386-linux-gnu/ld-2.15.so -rw-r--r-- 1 root root 143K Mar 20 2013 libdevmapper.so.1.02.1 lrwxrwxrwx 1 root root 16 Apr 30 2012 libfuse.so.2 -> libfuse.so.2.8.6 -rw-r--r-- 1 root root 179K Mar 2 2012 libfuse.so.2.8.6 ...
With the pwd command to show you where you are, the cd command to move to a new directory, and the ls command to show you the contents of a directory, you have the basic tools you need to navigate through your Linode's files and directories. To learn more about navigating directories, read the linked section of the Using the Terminal guide.
One of the easiest ways to upload your own files to your Linode is with a Secure FTP (SFTP) program. The Migrate from Shared Hosting to Linode article has a great walkthrough for how to do this.
Linux uses a powerful system of users and permissions to make sure that the right people get access to the right files. For example, as the owner of your Linode, you should to be able to view, edit, and run every file on the system. On the other hand, you want the general public to be able to view, but not change, your website files, and you don't want them to see the more structural files on your server at all. A different user, such as someone with a mailbox on your Linode, should be able to access their own files but not anyone else's. There are three permission categories:
The next concept to learn about is permissions. Every file and directory on your Linux system has three possible access levels: read, write, and execute. A readable file can be viewed. A writeable file can be edited. An executable file (like an application file) can be run. Running is what happens when you start up a program or script, either on your home computer or your Linode.
When you combine the concepts of users and permissions, a flexible and powerful system for controlling file access emerges. Each file has read, write, and execute permissions for its user, group, and everyone categories. Remember the list of directories from the last section? Now we'll find out what more of those items mean, by looking at an example directory called my_directory:
drwxr-xr-x 13 user1 group1 4.0K Nov 6 16:04 my_directory
The user and group are listed in the middle. In this case, the user is user1 and the group is group1. The user is listed first and the group second. The permissions are listed at the beginning of the line. Ignoring the first character, you can see that the permissions for the my_directory directory are rwxr-xr-x.
The user permissions are shown first. In this case, the user, user1, has read, write, and execute permissions, rwx. The group permissions are shown second. Here, everyone in the group1 group has read and execute permissions, but not write permissions, r-x. This means that members of the group1 group can view the contents of the my_directory directory, and run files in it, but not change them. The everyone permissions are listed last. Everyone can read and execute the files in the var directory, but not change them, because the permissions for everyone are again r-x.
To view the users and permissions for a particular file or directory, run the ls -l command, replacing my_directory with the name of your own file or directory:
ls -l my_directory
To learn about users and groups in more detail, read the Linux Users and Groups article.
While you could just use your Linode as a big hard drive for storing files, most people will want to install software on their servers. This section shows you how to install, run, update, and uninstall software from a Linux system.
Like most things in Linux, installing software is accomplished by typing and executing a specific text command. The most popular Linux distributions come with package managers that make it relatively easy to install and uninstall software on your Linode. Debian and Ubuntu use the Advanced Packaging Tool (APT) package manager, and Fedora and CentOS use the Yellowdog Updater, Modified (yum) package manager. Since we've been working with the Ubuntu 12.04 distribution so far, let's look at an example with APT. The command below shows you how to install the web server Apache, which lets you display websites:
apt-get install apache2
apache2 is the name of the package for Apache in the Ubuntu repositories. A package is a piece of software. Repositories are collections of software for your Linux distribution. The apt-get command is smart enough to look up an Ubuntu repository (specified on your system), find the apache2 package, and install it along with anything else you need for Apache.
The general form of the installation command for Ubuntu and Debian systems is:
apt-get install software
Just replace the word software in the command above with the package name for the software you want to install. There are thousands of different programs available to install on your server. If you search online for the software you need, you can find the correct package names to use with the APT installer. For example, if you searched for "ubuntu web server," you would find information about the Apache web server, and its package name, apache2.
Using yum on Fedora and CentOS systems is just as easy:
yum install software
Our Quick Start Guides series contain basic instructions for installing and configuring many common types of Linux software. The Hosting a Website guide shows you how to install software to run a website, while Running a Mail Server is for email servers.
There are three main ways to run programs in Linux.
You want some programs, like your web server, to run constantly. These are the programs that run as services on your Linode. For example, your web server keeps your website visible, so you want it to stay on all the time. Server processes that stay running in the background are known as daemons. To start a daemon, run the following command, replacing software with the name of the software you want to run. The name will be the same one you used to install it (for example, apache2 for Apache):
service software start
Sometimes you want to run a program on an as-needed basis. For example, you might want to run a script to rename a group of files. In that case, first use the cd command to move into the directory where the script is located. Make sure that your user has execute permissions for the script file. If you need to modify the permissions, see the Linux Users and Groups guide. Then run the script with the following syntax:
Finally, sometimes you want to run a program at regular intervals, as in the case of a daily backup script. The best way to do this is with the cron tool. Read the Schedule Tasks with Cron article to learn more. Scripts that you run this way also have to be executable.
Updating software is about the easiest thing you will ever do on a Linux system. As long as you installed your software with a package manager, just use APT or yum to update your entire system at once. Here's the command for Debian and Ubuntu:
apt-get update apt-get upgrade --show-upgraded
Or, for Fedora and CentOS:
That's it! Your packages are now up to date.
Updating your software is good for your system security. In most cases updates will go smoothly, but it's possible that some updates may break something on your server. It's always wise to make a backup of your system before updating it.
If you need to uninstall software, use the apt-get remove command:
apt-get remove software
If you also want to remove all configuration files associated with the software, run this command instead:
apt-get purge software
Here's the yum version for Fedora and CentOS:
yum remove software
When you run a Linux system, you are in charge of its security. The Internet is full of people who want to use your Linode's computing power for their own goals. If you neglect changing default passwords, install out-of-date software, or leave any other loophole, it's only a matter of time before your system gets hacked. You should go through the Securing Your Server article to tighten up your server's security.
Let's conclude our introduction to Linux with a discussion of different distributions. Despite many differences, RedHat Linux (which includes Fedora and CentOS) and Debian Linux (which includes Ubuntu) share a large amount of code with each other; the kernels are largely the same, and most of the user utilities and applications from the GNU project are the same. The differences between distributions generally relate to the specific goals and aims of the system developers, and which bundles of software are installed by default.
For instance, some distributions are designed to be as simple and minimalistic as possible, while others are designed to contain the most current, bleeding-edge software. Still others aim to provide the greatest amount of stability and reliability. In addition to the personality of each distribution, which you'll have to discover for yourself, there are a number of factors that you might find useful when choosing a distribution.
Different distributions of Linux are right for different situations. You should experiment until you find the best fit for you. Given the similarities between different distributions, don't be afraid switch to a new one that will serve you better. If you're familiar with the concepts in this article, you're well on your way to administrating your system like a pro with any distribution of Linux.
You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.
This guide is licensed under a Creative Commons Attribution-NoDerivs 3.0 United States License.
Last edited by Sharon Campbell on Thursday, December 19th, 2013 (r4038).