This is the Linux Lab I wrote for the University of Plymouth Official Computer and Information Security Society for the 2018/19 Academic Year.
Originally written for Pandoc to output as a PDF, it is now available using Hugo.
This tutorial was designed around the Ubuntu virtual machines available in the security lab on campus. As such, it may not be immediately useful to anyone trying to follow it.
The text that follows is mostly unchanged - exceptions are noted in the Version History.
Finally, I would like to clarify that the contents and advice herein don’t necessarily reflect what I believe today, and almost certainly not what I will believe in the future!
All of that said, enjoy.
Please note that I refer to the operating system as “Linux” for the sake of brevity. It may be more pertinent to say GNU/Linux for most distributions.
I would like to thank the Debian maintainers, past and present, for their work in making a rock solid GNU/Linux distribution. Without which, this tutorial would never have been made.
Copyright and Licence Notices
Copyright (C) 2020, 2022 James Davidson Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
About the Linux Lab
The Linux Lab is a tutorial designed for beginners; it aims to be comprehensive and technical.
There are no requirements to undertake the Linux Lab, with the exception of installing a Linux distribution to practice on.
- Removed hyperlink to Version 1.2.0
Released on 17/07/2022.
|Description: “A tutorial for beginners”||Title: From “Linux Lab” to “The Linux Lab”||Introduction: Text denoting an update occured after Version 1.2.0||About: Link to GitLab repository|
|Introduction: Explanation of GNUs role in the Linux operating system||Semantic versioning to incrementing whole numbers|
|YAML: SEO tags||Table of Contents: Hugo shortcode to Gokarna YAML|
|YAML: Weight for post popularity||GNU Free Documentation License: Licence text from Markdown to plain text|
|Heading IDs (see links in this table)||GNU Free Documentation License: Heading from “Licence Text” to “GNU Free Documentation License”|
|Date: To coincide with this release|
Version 1.2.0 - 11/06/2022
- Replaced Pandoc YAML
- Added Introduction
- Updated copyright year
- Removed references to ‘series of tutorials’ and future labs
- Clarified that the
linux-labrepository contains prior versions
- Added dates to document versions
- Corrected a missing plural
- Removed quote characters
- Added missing code fencing
Version 1.1.0 - 17/06/2020
- Changed fonts to Liberation (PDF version only)
- Added more Tasks
- Added Presentation contents
Version 1.0.0 - 11/01/2020
- Initial release
Basic shell commands
You should already be using
You can ascertain which login shell you are using by issuing the command:
bash is a feature-rich shell, and has many built-in commands. Here, we will use two builtins:
By default, you should be placed in the logged-in user’s home directory:
echo $HOME && pwd
If the two outputs match, you are currently in the
You may notice that the information in the above output is already present in your terminal prompt!
Your terminal prompt should look similar to this:
This prompt gives us important information about the status of the terminal window:
- User (whoami)
- Hostname (hostname)
- Working directory (pwd)
- Execution mode ($ or #)
Thus far, we have been referencing WORDS preceded by dollar signs ($). These are called environment variables.
Environment variables define properties of the running system.
Just like a variable in a programming language, environment variables are ‘dynamic values which affect the processes or programs on a computer’.
We can query environment variables to determine how a system is configured:
Right now, you are using a terminal emulator. In Ubuntu, this should be
gnome-terminal by default:
gnome-terminal should report itself as
We’ve covered a couple of shell builtins, so we’ll move onto external binaries.
Binaries are compiled and linked programs. External refers to the fact that such programs are not internal to the shell, and can be run from any shell (not just
As we are already in the home directory, let’s see which directories and files are inside it:
You should see typical directories such as Documents and Downloads. We can verify which directories are created by default:
This command opens the manual page for the
xdg-user-dir program. It contains the names of default user directories in
$HOME, as created by
In Ubuntu, you may notice the results of
ls are coloured. This is because Ubuntu ships with aliases.
The following command will reveal what the aliased command does:
Similarly, you can use the builtin
alias to list all aliases.
You should see that the GNU option
--color=auto is used. Options (sometimes called switches) allow you to change a program’s behaviour.
For example: to list in long format, showing almost all entries (excluding . and ..), with human readable data units:
Interestingly, because the
ls program itself is aliased, every
ls command issued will use the
You can discover the options that exist for a program by consulting its man page:
Navigating the shell
To change directory, use
When seeking directories and files, you can press the TAB key twice to display matches.
Try navigating to the
/etc/apt directory using autocompletion.
Manipulating files and directories
You can create directories using
mkdir. Empty files can be created with
mkdir dirkthediring touch dirkthediring/filebreathingdragon
You can view the contents of your new directory, and the contents of every other directory inside
~, with a wildcard:
Files and directories can be moved, or renamed, with
mv dirkthediring/ rincewind/ mv rincewind/filebreathingdragon rincewind/theluggage
Bear in mind, you can elect to
cd into these directories when working in them (hence ‘working directory’).
You can also use autocompletion to speed up the renaming process (ergo avoiding typing).
Files and directories can be copied with
cp rincewind/theluggage ~
Here, we can see the source file
theluggage, located in
rincewind/ is copied to the target directory,
Note how the file name need not be written again, as it is preserved.
You can remove files and directories with
rm -ri rincewind/
Note the options listed after
rm, and their effect on the resulting command.
Consult the man page to establish what these options do.
When listing the contents of
~ again, we can see
rincewind/ is missing:
ls * | grep -w rincewind
grep looks for patterns. The pipe operator ( | ) is used to feed data from one command into another. In this case, the output of
ls is fed to
grep so we can search for
Note that the use of
ls | grep is discouraged. Instead, you should use
find, which is covered later in the tutorial.
grep is useful for locating patterns in the contents of files. For example, locating the current user in the
grep $(whoami) /etc/passwd
Here, we can see the user’s home directory and their login shell.
Don’t worry about the finer details of
/etc/passwd at this stage.
grep provides us a clean summary of instances of a pattern in a file.
grep’s output is coloured, like
ls. Try issuing
type again to identify what the real command is!
We can use
less to read the file in full.
There is a lot of information in this file, and it can be difficult to read through without syntax highlighting.
Thankfully, you can search in
- Press the forward slash ( / ) key
- Type your search term: student
- Press ENTER
less will place us on the line where the pattern first occurs. We now see the same information
Let’s try another term, this time bin. Observe how all the matches are highlighted:
- Press ’n’ to go to the next match
- Press ‘Shift + n’ (SHIFT-n) to go to the previous match
Our copied file,
theluggage still exists:
find ~ -name theluggage
find searches for files in the given directory hierarchy. Here, we have specified
We can view instances of
cat using find. To do this, we start in the root directory
find / -name cat
You’ll notice many ‘Permission denied’ errors - this is because the
student user doesn’t have the permissions to view certain directories and files.
Let’s see who owns
ls -ld /bin ls -lA /bin
/bin and its constituent files are owned by
root. Due to this, we cannot search
/bin as the current user.
To resolve this, we can use
sudo executes commands as another user - by default, the superuser (root).
To avoid typing the
find command again, we can use
bash’s reverse history search function:
- Use the keyboard combination: Control + R (Ctrl-R)
- Type the search term: find
- Press the left or right arrow key
Prepend the command with
sudo find / -name cat
The command now completes successfully, and we can see
Phew, that was a great deal of commands!
If you’ve reached this point, take a well earned 10 minute break.
Regular breaks make you a better learner!
During this part of the lab, we will learn how to use
vim was used to create this worksheet in Markdown!
vim is included on virtually 100% of Linux installs. Hence, learning how to use it is vital!
vim is different to every text editor you’ve ever used before
Now that I’ve scared you, let me explain…
vi) is a modal text editor, and makes use of modes and motions.
- Allows you to navigate in a file (moving to words, lines, et cetera).
- You can use motions in Normal mode to manipulate text.
- Every other editor you’ve used is permanently in Insert mode.
- Insert mode is for typing, and typing only!
- When you want to manipulate text, you use one of the other modes.
- Used for complex commands, which can’t be achieved in Normal mode.
- For example, Find and replace:
- Used to make text selections.
- You can move with normal cursor movements, by line, or by block,
- For typing over existing text.
- Every character typed replaces an existing character.
I don’t use Replace mode. You can achieve superior manipulation with motions in Normal mode.
Motions are the real power behind vim.
From the off: the h, j, k and l keys are used in lieu of the arrow keys.
Why? Because your fingers never need to leave the main area of the keyboard!
Not to be confused with shell operators.
Motions are used in Normal mode. Here are two important operators:
- c is used to change
- d is used to delete
Operators are used before motions.
Using these operators, we can change the following line:
"Hello world! vim is better than emacs!" d3w "vim is better than emacs!"
With just three keystrokes, the content of the line has changed:
- d signifies that we want to delete something
- 3 is the number of something we want to delete
- w indicates that something should be words
vim motions are natural, and are designed to be an extension of what you want to achieve in the editor.
As mentioned earlier, hjkl are used in place of the arrow keys:
- h - left
- j - down
- k - up
- l - right
While unnatural at first, hjkl is decidedly faster than the arrow keys.
There are more useful navigation motions:
0 - move to the first character in a line
^ - move to the absolute beginning of a line
$ - move to the end of a line
gg - move to the beginning of the file
Shift + G (S-G) - move to the end of the file
Move over words.
- w - move forwards to the beginning of a word
- e - move forwards to the end of a word
- b - move backwards to the beginning of a word
- ge - move backwards to the end of a word
Putting it all together
With the motions defined above, we can navigate around a file.
I have consciously limited the quantity of motions we will learn today.
Let’s try editing a file now:
- Open a vim buffer, naming the file: brainiac
Enter Insert mode by pressing i
Type the following:
The quick brown fox jumps over the lazy dog
Exit Insert mode by pressing ESCAPE
Use word motions to move around the line
As we progress, allow yourself to acclimate to using motions before continuing.
Move to the word brown and replace it with platinum
From Normal mode, write the changes to disk
- Press ENTER
Quit by issuing
You can combine motions in command mode. For example,
:wq, which writes changes and quits.
ZZ can also be used to exit vim, while saving any changes made.
:help to query the plethora of commands and motions in vim.
More on motions
- o - enter Insert mode on next line
- O - enter Insert mode on previous line
Remember to combine your motions. For example, when moving between lines:
- 3j - move down three lines (from your cursor position)
- 5G - move to (absolute) line 5
To help you navigate, you can make use of numbering:
:set number :set relativenumber
- number is absolute
- relativenumber is relative to the line your cursor is on
You can also highlight the line your cursor is on:
You should be able to answer all of these questions using the knowledge gained from the tutorial.
Please do not refer to websites, or use tools outside of the terminal. If you are stuck, re-read the tutorial to guide you.
When recording answers for the tasks, use
vim. We will review your answers when everyone has finished the lab.
How would you create a new directory, and a subdirectory within it, in one command?
You may not use operators such as
Hint: Use the man page.
What command would you use to go to the home directory?
How would you print the working directory?
How would you create a file with the contents “Hello World”?
You may not use a text editor.
Hint: Using an operator.
How can you remove an empty directory, without using
Hint: Use a similarly named programs’
How would you log in as the root user?
How would you move to the previous working directory?
How would you create your own aliases?
How would you recursively long list subdirectories, without displaying the owner or group?
How would you change the access and modification time of a file?
Health warning: You may begin to grow a Richard Stallman-esque beard if you can successfully complete these additional tasks.
Where would you permanently add aliases to an interactive shell?
How would you safely edit a file owned by the root user?
How would you symbolically link a file?
List all methods.
Hint: Using a program already covered, and another related to linking.
How would you change ownership of a file?
How would you modify permissions of a file?
How would you list all environment variables in one command?
You may not use operators such as
How would you change your default text editor in a Debian (or derivative) system?
Hint: This question strictly relates to a program provided by Debian (which Ubuntu is derivative of).
Hint: Using the Alternatives system.
Advice for installing GNU/Linux
To become proficient with Linux, you should use it every day! To do this, you should select a distribution.
However, not all distributions are made equal. My advice is to use Debian.
You may also like to try other independent distributions, such as Fedora or Solus.
Don’t use derivative distributions like Ubuntu, Linux Mint or Manjaro. And definitely don’t use advanced distributions like Arch, Void or Gentoo.
Many individuals dual boot a Windows operating system with GNU/Linux. There are some vital considerations to make before doing so:
Windows, after an update, will purposely remove Linux filesystems from unencrypted partitions
To overcome this, use full disk encryption. In the distribution installer, elect to encrypt with LUKS.
dskmgmton Windows to reduce the size of your Windows system (C:) partition
Install Linux alongside, and after, Windows. If you install Linux first, Windows’ Master Boot Record will overwrite the Linux bootloader.
Alternatively, install Linux onto another drive.
Don’t forget to install a bootloader, which allows you to boot into Linux or Windows
Always read your distribution’s documentation on installation
There is no substitute for the advice of the distribution maintainers, as they know how to properly configure the system.
Be aware of the intricacies of a Linux install
- Partition tables (GPT or MBR)
- Partitioning schemes (
- EFI or BIOS
On motherboards made in the last decade, this is likely UEFI.
Debian offers a resilient installer, which deftly automates the boring elements of installation. Chiefly, this relates to partitioning (traditional volumes or Logical Volume Manager) and encryption (LUKS).
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- FUTURE REVISIONS OF THIS LICENSE
The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/licenses/.
Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.
“Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.
“CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.
“Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.
An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.
The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.
ADDENDUM: How to use this License for your documents
To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:
Copyright (c) YEAR YOUR NAME. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".
If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:
with the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.
If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.