Beginner: Linux Navigation Manual

Welcome to the Linux world! Whether you’re just starting on an intro to CS course or wandering through your very first UNIX-based home server, learning how to navigate around in Linux (more specifically, using the command line) is going to make your life much easier and much much more powerful.

There are many distributions of Linux out there. Each of them has its own variation of commands to work with. Specifically for this tutorial, I’m going to be using Ubuntu 14.04.2 LTS on Cloud9. Keep in mind that all commands demonstrated here will probably be usable on earlier and future versions of Ubuntu, as well as Debian and Debian-based distros.

To check for the distribution and version number, simply type this into the terminal.

Not only do different distros have different commands, they also have different default shell (scripting environment). What this means is that this window — often called the terminal — works differently.

In this case, I’m going to be using Bash (short for Bourne-Again Shell), which is the default shell for Ubuntu and Debian.

In Bash, you’ll typically be presented with this kind of prompt:

where brillydev is my username, and ~/workspace is the directory I’m currently in, followed by a dollar sign ($), or depending on some user, a hash (#).

Because I’m lazy, I’m going to omit that brillydev:~/workspace, and leave only $ when I show you my terminal window. You don’t need to type all of these brillydev:~/workspace $ when you type the command.

Oh, and keep in mind that Linux is case-sensitive. A is different from a!

pwd (print working directory) shows the current directory (basically, the folder) you’re in.

In case you’re wondering:

• ~ (tilde) means the user’s home directory, usually /home/username

• . (dot) means the current directory you’re in

• .. (dot dot) means the parent directory of the current directory you’re in.

  For example, if you’re in foo/bar/, . will represent bar/, .. will represent foo/.

The most basic command of all time, cd (change directory) means... Err, change directory.

You can see that the directory changes according to what you type after cd. Typing cd alone without any argument (without anything that follows it) will bring you to the home directory of the user.

cd followed by a dash (-)will bring you to the recent directory you were in.

ls (list) list down all the content inside the directory.

A slash (/) post-fixed after a name indicates that it is a directory. In this case, bar and foo are directories. Anything not with a slash are all files.

In addition to performing a general task, a command may also contain flags to specify a specific task you want the command to do. A flag is anything prefixed with a dash (-) that follows the command name.

For example, you can type ls -l. In this case, l being the flag, to display the content of the directory in a nice list view.

Flags can also be combined. ls -a display all content, including hidden files (files that are prefixed with a dot). When used with ls -l, we can combine them like this:

Some flags can also be more than one-letter long. Those that are multiple letters long can be written with double dashes in front. For instance, ls -a can also be written as:

For those who want more fancy visualization, tree is for you.

You’re having fun playing around with all these commands when you realize you screen is really cluttered and you need some clean up. Typing clear or reset or input any of the key combinations mentioned will get your terminal wiped up.

Surprisingly not many beginners know how to run a standalone binary/executable file. To execute a local file, simply type

If you ever find yourself stuck in the program, simply press Ctrl + C to get out.

If shutting down the system is frustrating to you, here is the way to do it.

To restart the computer:

To log out:

or simply press Ctrl + D.

If any of these don’t work, adding a sudo in front will probably help.

mkdir (make directory) is used to create a directory.

To move files, the command mv (move) is used.

Interestingly, it can also be used to rename things as well!

And if you’re tired of typing ls everytime after the command, a semicolon can condense your code into one line. This produces the same effect:

rm (remove) removes files. Take note that this action cannot be undone.

rm cannot be used with directories, unless accompanied by -r flag (short for recursive). What this means is that rm will go into every directory in the specified path and delete files one by one, recursively up each directory inside. If you don’t understand this, it’s fine, unless you do programming. Just remember that it deletes all the files and directories in the specified path.

If you’re tired of typing ys for all the files, rm -rf can help you. Be extremely careful, however, as this command-flag combination is incredibly dangerous. If you accidentally type the wrong path — boy, there’s no going back!

If you try to use rm alone for directories, you’ll be faced with this:

In this case, rmdir (remove directory) can be used instead. Note also that this command can only be used with empty directories.

When you wish to create new (empty) files, use touch.

Copying is undeniably one of the greatest inventions of all time. To do that, use cp (copy).

To copy a directory recursively, use cp -r.

You’ll encounter this quite often in the future. So it’s probably good to know it now. To create a symbolic link (Google for explanations), use ln -s.

echo prints out whatever you say to it.

To display the content of a file, use any of the commands above.

These commands don’t do exactly the same thing. Do some little experiments to find out how they differ :)

grep is an extremely powerful tool to search the content of a file. It prints out the line containing the word(s) specified, if it is present in the file. For example.

(actual result will have blah blah blah highlighted)

There are a lot more powerful tools out there, such as sed and awk, that will unleash your potential in Linux. We can’t cover all of them here, so be sure to do some research to find out more about them!

If you happen to forget, or see a new command you’ve never heard of, apart from Google, your user manual will also be incredibly helpful. To use it, simply type man.

| (that vertical bar right above the Enter key) is called a pipe. It redirects the output of the left command to the input of the right. For example:

Redirections are similar to pipe; but instead of passing the output as an input, they save the output to a file, or read the content of a file.

• > saves the output to a file
• < reads the content of a file

Redirection overwrites the files each time it is used. Use appends (>> and <<) should you decide to not overwrite them, and append instead.

Working with computers nowadays usually requires external software from the Internet. You can choose to download these external software files manually or use a package manager to manage all the stuff for you. apt-get (advance packaging tool) is the default package manager for Ubuntu and Debian.

If you ever get stuck, sudo can help you.

wget is a tool to download files from the Internet.

Sometimes you’ll get files in archived form. To extract them, use unzip or tar.

vi or vim (vi improved) is an awesome tool to do all things text. It’s incredibly difficult to use at first, but through time, you’ll realize that it’s one of the best out there.

For instructions, I recommend this awesome interactive guide:

Interactive Vim Tutorial

If you’re kinda lazy to learn vim, nano is a simple intuitive alternative.

All-time rival of vim, here comes emacs.

Remember this?

Those arcane characters on the leftmost column are where your permission settings lie. To characterize, there are three main permissions you can set for a file or a directory: read, write and execute, represented by r, w and x respectively.

The permissions are arranged in the following order: user, group and others.

For example,

This means that the user (owner of apple.txt) can read and write to apple.txt, the user group which the owner of apple.txt is in, as well as other people from somewhere else can only read apple.txt.

Execute, in the context of a directory, also means access. Hence if you deny permission to execute a directory, you can’t access it.

To change permissions, chmod (change mode) can be used. I leave it to you to interpret what this means :P

Similar to chmod, chown (change owner) changes the owner of the file.

You can find out more about ssh (secure shell) from the Internet.

Not a command, but helpful to know. If you notice, all the commands here are really just compiled binary files underneath the hood. To know where they stay, check out:

Differences between /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/bin, /usr/local/sbin

Phew! That was an awful lot of stuff! Use it often, and you’ll remember all the commands by heart. For now, this cheat sheet may be of help.

FOSSwire Linux/UNIX Command Reference

Keep in mind that there are still tons of things which I did not cover in this tutorial. In fact, I didn’t even go into details about how these commands work. Because this tutorial is only designed to be a broad overview (for absolute beginners), I encourage you to dive in further and actually do stuff with it.

But if you’re still not very confident, or maybe you got lost in this tutorial, that’s okay too! There are many alternatives out there on the Internet, but be warned that not a lot of them are beginner-friendly. I also recommend checking out Ryan's Linux Tutorial for more explanations and use cases.

Good luck :)