The Linux Lab

Introduction

This is the Linux Lab I wrote for the University of Plymouth Official Computer and Information Security Society for the 2019/20 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.

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!

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.

Acknowledgements

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.

Version History

The last modified date matches the latest release. This change won’t be explicitly noted for each version.

Version 6

Released on 2022-12-09.

• Introduction

  • Changed case of “Academic Year” to “academic year”
  • Removed “Finally,” from “I would like to clarify …”
  • Removed “All of that said, enjoy.”
  • Fixed the academic year from “2018/19” to “2019/20”

• Version History

  • Added notice to reflect that changes to the last modified date won’t be tracked in changelogs
  • Added Version 5’s missing release date
  • Changed dates to follow the ISO 8601 standard
  • Changed Version 1.0.0, 1.1.0 and 1.2.0 from nested lists to headings

Version 5

Released on 2022-09-19.

• Removed hyperlink to Version 1.2.0

Version 4

Released on 2022-07-17.

Version 1.2.0

Released on 2022-06-11.

• Replaced Pandoc YAML
• Added Introduction
• Updated copyright year
• Removed references to ‘series of tutorials’ and future labs
• Clarified that the linux-lab repository contains prior versions
• Added dates to document versions
• Corrected a missing plural
• Removed quote characters
• Added missing code fencing

Version 1.1.0

Released on 2020-06-17.

• Changed fonts to Liberation (PDF version only)
• Added more Tasks
• Added Presentation contents

Version 1.0.0

Released on 2020-01-11.

• Initial release

Basic shell commands

You should already be using bash!

Login shell

You can ascertain which login shell you are using by issuing the command:

echo $SHELL

builtins

bash is a feature-rich shell, and has many built-in commands. Here, we will use two builtins: echo and pwd.

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 /home/$USER directory!

Terminal prompt

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:

student@ubuntu:~$

This prompt gives us important information about the status of the terminal window:

• User (whoami)
• Hostname (hostname)
• Working directory (pwd)
• Execution mode ($ or #)

Environment variables

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:

Terminal emulator

Right now, you are using a terminal emulator. In Ubuntu, this should be gnome-terminal by default:

echo $TERM

gnome-terminal should report itself as xterm.

External binaries

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 bash).

As we are already in the home directory, let’s see which directories and files are inside it:

ls

You should see typical directories such as Documents and Downloads. We can verify which directories are created by default:

man xdg-user-dir

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 xdg-user-dirs-update.

Aliases

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:

type ls

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:

ls -lAh

Interestingly, because the ls program itself is aliased, every ls command issued will use the --color=auto option.

You can discover the options that exist for a program by consulting its man page:

man ls

Navigating the shell

To change directory, use cd.

Tab autocompletion

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

Creation

You can create directories using mkdir. Empty files can be created with touch.

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:

ls *

Moving

Files and directories can be moved, or renamed, with mv.

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).

Copying

Files and directories can be copied with cp.

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.

Removal

You can remove files and directories with rm.

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

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 rincewind/.

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 /etc/passwd file.

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 whoami and /etc/passwd at this stage.

less

Using 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.

less /etc/passwd

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 less:

• 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 grep printed.

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

Finding files

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 /bin:

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. sudo executes commands as another user - by default, the superuser (root).

Recursive search

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

sudo

Prepend the command with sudo:

sudo find / -name cat

The command now completes successfully, and we can see /bin/cat.

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!

Text editing

During this part of the lab, we will learn how to use vim.

vim was used to create this worksheet in Markdown!

Like bash, 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…

vim (or vi) is a modal text editor, and makes use of modes and motions.

Modes

• Normal

  • Allows you to navigate in a file (moving to words, lines, et cetera).
  • You can use motions in Normal mode to manipulate text.

• Insert

  • 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.

• Command

  • Used for complex commands, which can’t be achieved in Normal mode.
  • For example, Find and replace: :%s/foo/bar

• Visual

  • Used to make text selections.
  • You can move with normal cursor movements, by line, or by block,

• Replace

  • 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

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!

Operators

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.

Navigation motions

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

Word motions

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:

1. Open a vim buffer, naming the file: brainiac

vim brainiac

2. Enter Insert mode by pressing i

3. Type the following:

   The quick brown fox jumps over the lazy dog

4. Exit Insert mode by pressing ESCAPE

5. Use word motions to move around the line

As we progress, allow yourself to acclimate to using motions before continuing.

6. Move to the word brown and replace it with platinum

7. From Normal mode, write the changes to disk

   • Type :w
   • Press ENTER

8. Quit by issuing :q

You can combine motions in command mode. For example, :wq, which writes changes and quits.

:x and ZZ can also be used to exit vim, while saving any changes made.

Use :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

Helpful commands

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:

:set cursorline

Tasks

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.

1. How would you create a new directory, and a subdirectory within it, in one command?

   You may not use operators such as && or ;

   Hint: Use the man page.

2. What command would you use to go to the home directory?

3. How would you print the working directory?

4. How would you create a file with the contents “Hello World”?

   You may not use a text editor.

   Hint: Using an operator.

5. How can you remove an empty directory, without using rmdir?

   Hint: Use a similarly named programs’ man page.

6. How would you log in as the root user?

7. How would you move to the previous working directory?

8. How would you create your own aliases?

9. How would you recursively long list subdirectories, without displaying the owner or group?

10. How would you change the access and modification time of a file?

Intermediate tasks

Health warning: You may begin to grow a Richard Stallman-esque beard if you can successfully complete these additional tasks.

1. Where would you permanently add aliases to an interactive shell?

2. How would you safely edit a file owned by the root user?

3. How would you symbolically link a file?

   List all methods.

   Hint: Using a program already covered, and another related to linking.

Advanced tasks

1. How would you change ownership of a file?

2. How would you modify permissions of a file?

3. How would you list all environment variables in one command?

   You may not use operators such as && or ;

4. 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.

Dual booting

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.

• Use dskmgmt on 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 (/boot, / and /home)
  • 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).

GNU Free Documentation License

            GNU Free Documentation License
             Version 1.3, 3 November 2008

Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. https://fsf.org/ Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional and useful document “free” in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

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The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

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A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

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The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you may publicly display copies.

3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

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4. MODIFICATIONS

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A. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission. B. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement. C. State on the Title page the name of the publisher of the Modified Version, as the publisher. D. Preserve all the copyright notices of the Document. E. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices. F. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below. G. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice. H. Include an unaltered copy of this License. I. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence. J. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission. K. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein. L. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles. M. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version. N. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section. O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties–for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements”.

6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

8. TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

10. 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.

11. RELICENSING

“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.