Linux there are GUIs (graphical user interfaces), where you can point
and click and drag, and hopefully get work done without first
reading lots of documentation. The traditional Unix environment is a
CLI (command line interface), where you type commands to tell the
computer what to do. That is faster and more powerful, but requires
finding out what the commands are."
-- from man intro(1)
There are many varieties of Linux, but almost all of them use similar commands that can be entered from a command-line interface terminal.
There are also many graphical user interfaces (GUIs), but each of them works differently and there is little standardization between them. Experienced users who work with many different Linux distributions therefore find it easier to learn commands that can be used in all varieties of Ubuntu and, indeed, in other Linux distributions as well.
For the novice, commands-line interface commands can appear daunting:
sudo gobbledegook blah_blah -w -t -f aWkward/ComBinationOf/mixedCase/underscores_strokes/and.dots
However, it is important to note that even experienced users often cut and paste commands (from a guide or manual) into the command-line terminal; they do not memorize them.
It is important, of course, to know how to use the command-line terminal - and anyone who can manage typing, backspacing, and cutting and pasting can manage the command-line terminal (it is not more difficult than that).
This page will outline a few crafty shortcuts which can make using a command-line interface easier.
All command names will be in bold.
Commands needing to be typed will be in "bold with quotes".
Note that the terminal is case sensitive. User, user, and USER are all different to Linux.
Unity is the default Desktop Environment used in 11.04. Where systems are not ready for Unity they revert to Gnome which is also used in previous releases such as Ubuntu 10.04 LTS (Lucid), see next sub-section.
The easiest way to open the Terminal is to use the 'search' function on the dash. Or you can click on the 'More Apps' button, click on the 'See more results' by the installed section, and find it in that list of applications. A third way, available after you click on the 'More Apps' button, is to go to the search bar, and see that the far right end of it says 'All Applications'. You then click on that, and you'll see the full list. Then you can go to Accessories > Terminal after that. So, the methods in Unity are:
Dash -> Search for Terminal
Dash -> More Apps -> 'See More Results' -> Terminal
Dash -> More Apps -> Accessories -> Terminal
Keyboard Shortcut: Ctl + Alt + T
Gnome is the Classic Desktop Environment for Ubuntu 11.04 (Natty) and is the default DE in earlier releases, such as Ubuntu 10.04 LTS (Lucid).
Applications menu -> Accessories -> Terminal.
Applications menu -> System -> Terminal.
KMenu -> System -> Terminal Program (Konsole).
Menu -> Accessories -> LXTerminal.
Most of the following commands will need to be prefaced with the sudo command. This elevates privileges to the root-user administrative level temporarily, which is necessary when working with directories or files not owned by your user account. When using sudo you will be prompted for your password. Only users with sudo (administrative) privileges will be able to use this command.
The tilde (~) symbol stands for your home directory. If you are user, then the tilde (~) stands for /home/user
pwd: The pwd command will allow you to know in which directory you're located (pwd stands for "print working directory"). Example: "pwd" in the Desktop directory will show "~/Desktop". Note that the Gnome Terminal also displays this information in the title bar of its window. A useful gnemonic is "present working directory."
ls: The ls command will show you ('list') the files in your current directory. Used with certain options, you can see sizes of files, when files were made, and permissions of files. Example: "ls ~" will show you the files that are in your home directory.
cd: The cd command will allow you to change directories. When you open a terminal you will be in your home directory. To move around the file system you will use cd. Examples:
To navigate into the root directory, use "cd /"
To navigate to your home directory, use "cd" or "cd ~"
To navigate up one directory level, use "cd .."
To navigate to the previous directory (or back), use "cd -"
To navigate through multiple levels of directory at once, specify the full directory path that you want to go to. For example, use, "cd /var/www" to go directly to the /www subdirectory of /var/. As another example, "cd ~/Desktop" will move you to the Desktop subdirectory inside your home directory.
cp: The cp command will make a copy of a file for you. Example: "cp file foo" will make an exact copy of "file" and name it "foo", but the file "file" will still be there. If you are copying a directory, you must use "cp -r directory foo" (copy recursively). (To understand what "recursively" means, think of it this way: to copy the directory and all its files and subdirectories and all their files and subdirectories of the subdirectories and all their files, and on and on, "recursively")
mv: The mv command will move a file to a different location or will rename a file. Examples are as follows: "mv file foo" will rename the file "file" to "foo". "mv foo ~/Desktop" will move the file "foo" to your Desktop directory but will not rename it. You must specify a new file name to rename a file.
Note that if you are using mv with sudo you can use the ~ shortcut, because the terminal expands the ~ to your home directory. However, when you open a root shell with sudo -i or sudo -s, ~ will refer to the root account's home directory, not your own.
rm: Use this command to remove or delete a file in your directory.
rmdir: The rmdir command will delete an empty directory. To delete a directory and all of its contents recursively, use rm -r instead.
mkdir: The mkdir command will allow you to create directories. Example: "mkdir music" will create a directory called "music".
man: The man command is used to show you the manual of other commands. Try "man man" to get the man page for man itself. See the "Man & Getting Help" section down the page for more information.
df: The df command displays filesystem disk space usage for all mounted partitions. "df -h" is probably the most useful - it uses megabytes (M) and gigabytes (G) instead of blocks to report. (-h means "human-readable")
du: The du command displays the disk usage for a directory. It can either display the space used for all subdirectories or the total for the directory you run it on. Example:
user@users-desktop:~$ du /media/floppy 1032 /media/floppy/files 1036 /media/floppy/ user@users-desktop:~$ du -sh /media/floppy 1.1M /media/floppy/
-s means "Summary" and -h means "Human Readable"
free: The free command displays the amount of free and used memory in the system. "free -m" will give the information using megabytes, which is probably most useful for current computers.
top: The top command displays information on your Linux system, running processes and system resources, including CPU, RAM & swap usage and total number of tasks being run. To exit top, press "q".
uname -a: The uname command with the -a option prints all system information, including machine name, kernel name & version, and a few other details. Most useful for checking which kernel you're using.
lsb_release -a: The lsb_release command with the -a option prints version information for the Linux release you're running, for example:
user@computer:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 6.06 LTS Release: 6.06 Codename: dapper
ip addr reports on your system's network interfaces.
"adduser newuser" command will create a new general user called "newuser" on your system, and to assign a password for the newuser account use "passwd newuser".
The default behaviour for a command may usually be modified by adding a --option to the command. The ls command for example has an -s option so that "ls -s" will include file sizes in the listing. There is also a -h option to get those sizes in a "human readable" format.
Options can be grouped in clusters so "ls -sh" is exactly the same command as "ls -s -h". Most options have a long version, prefixed with two dashes instead of one, so even "ls --size --human-readable" is the same command.
man command, info command and command --help are the most important tools at the command line.
Nearly every command and application in Linux will have a man (manual) file, so finding them is as simple as typing "man "command"" to bring up a longer manual entry for the specified command. For example, "man mv" will bring up the mv (Move) manual.
Move up and down the man file with the arrow keys, and quit back to the command prompt with "q".
"man man" will bring up the manual entry for the man command, which is a good place to start!
"man intro" is especially useful - it displays the "Introduction to user commands" which is a well-written, fairly brief introduction to the Linux command line.
There are also info pages, which are generally more in-depth than man pages. Try "info info" for the introduction to info pages.
Some software developers prefer info to man (for instance, GNU developers), so if you find a very widely used command or app that doesn't have a man page, it's worth checking for an info page.
Virtually all commands understand the -h (or --help) option which will produce a short usage description of the command and it's options, then exit back to the command prompt. Try "man -h" or "man --help" to see this in action.
Caveat: It's possible (but rare) that a program doesn't understand the -h option to mean help. For this reason, check for a man or info page first, and try the long option --help before -h.
If you aren't sure which command or application you need to use, you can try searching the man files.
man -k foo will search the man files for foo. Try "man -k nautilus" to see how this works.
Note that this is the same as doing apropos command.
man -f foo searches only the titles of your system's man files. Try "man -f gnome", for example.
Note that this is the same as doing whatis command.
Users who have Konqueror installed will be pleased to find they can read and search man pages in a web browser context, prettified with their chosen desktop fonts and a little colour, by visiting man:/command in Konqueror's address bar. Some people might find this lightens the load if there's lots of documentation to read/search.
Often, you will be referred to instructions that require commands to be pasted into the terminal. You might be wondering why the text you've copied from a web page using ctrl+C won't paste in with ctrl+V. Surely you don't have to type in all those nasty commands and filenames? Relax. ctrl+shift+V pastes into a Gnome terminal; you can also do Middle Button Click on your mouse (both buttons simultaneously on a two-button mouse) or Right Click and select Paste from the menu. However, if you want to avoid the mouse and yet paste it, use "Shift+Insert", to paste the command. If you have to copy it from another terminal / webpage, you can use "Ctrl+Insert" to copy.
Up Arrow or ctrl+p
Scrolls through the commands you've entered previously.
Down Arrow or ctrl+n
Takes you back to a more recent command.
When you have the command you want.
A very useful feature. It autocompletes any commands or filenames, if there's only one option, or else gives you a list of options.
Searches for commands you've already typed. When you have entered a very long, complex command and need to repeat it, using this key combination and then typing a portion of the command will search through your command history. When you find it, simply press Enter.
The history command shows a very long list of commands that you have typed. Each command is displayed next to a number. You can type !x to execute a previously typed command from the list (replace the X with a number). If you history output is too long, then use history | less for a scrollable list.
The mouse won't work. Use the Left/Right arrow keys to move around the line.
When the cursor is where you want it in the line, typing inserts text - ie it doesn't overtype what's already there.
ctrl+a or Home
Moves the cursor to the start of a line.
ctrl+e or End
Moves the cursor to the end of a line.
Moves to the beginning of the previous or current word.
Deletes from the current cursor position to the end of the line.
Deletes the whole of the current line.
Deletes the word before the cursor.
You can also get it with a function key
You can run more than one - in tabs or separate windows
AptGetHowto - using apt-get to install packages from the command line.
Commandline Repository Editing - adding the Universe/Multiverse repositories through the command line.
grep Howto - grep is a powerful command line search tool.
find Howto - locate files on the command line.
CommandlineHowto - longer and more complete than this basic guide, but still unfinished.
HowToReadline - information on some more advanced customization for the command line.
For more detailed tutorials on the Linux command line, please see:
http://mywiki.wooledge.org/BashGuide - Bash guide suitable for beginners. One of the few to also teach good practice.
http://linuxcommand.org/ - basic BASH tutorials, including BASH scripting
http://linuxsurvival.com/index.php - Java-based tutorials
http://rute.2038bug.com/index.html.gz - a massive online book about system administration, almost all from the command line.
http://www.ss64.com/bash/ - a good list a commands.
http://tinyurl.com/ycyg4mk - Listing of 3 helpful sites from beginner to advanced scripting
Kubuntuguide -- concise and up-to-date information for both command-line and GUI users of Kubuntu
26th of June, 2011