1.4 Lesson 1

Linux has a modular approach where different parts of the system are developed by different projects and developers, each one filling a specific need or objective. Because of that, there are several options of desktop environments to choose from and together with package managers, the default desktop environment is one of the main differences among the many distributions out there. Unlike proprietary operating systems like Windows and macOS, where the users are restricted to the desktop environment that comes with their OS, there is the possibility to install multiple environments and pick the one that adapts the most to you and your needs.

Basically, there are two major desktop environments in the Linux world: Gnome and KDE. They are both very complete, with a large community behind them and aim for the same purpose but with slightly divergent approaches. In a nutshell, Gnome tries to follow the KISS (“keep it simple stupid”) principle, with very streamlined and clean applications. On the other hand, KDE has another perspective with a larger selection of applications and giving the user the opportunity to change every configuration setting in the environment.

While Gnome applications are based on the GTK toolkit (written in the C language), KDE applications make use of the Qt library (written in C++). One of the most practical aspects of writing applications with the same graphical toolkit is that applications will tend to share a similar look and feel, which is responsible for giving the user a sense of unity during their experience. Another important characteristic is that having the same shared graphical library for many frequently used applications may save some memory space at the same time that it will speed up loading time once the library has been loaded for the first time.

For us, one of the most important applications is the graphical terminal emulator. Those are called terminal emulators because they really emulate, in a graphical environment, the old style serial terminals (often Teletype machines) that were in fact clients that used to be connected to a remote machine where the computing actually happened. Those machines were really simple computers with no graphics at all that were used on the first versions of Unix.

In Gnome, such an application is called Gnome Terminal, while in KDE it can be found as Konsole. But there are many other choices available, such as Xterm. Those applications are a way for us to have access to a command line environment in order to be able to interact with a shell.

So, you should look at the application menu of your distribution of choice for a terminal application. Besides any difference between them, every application will offer you what is necessary to gain confidence in using the command line.

Another way to get into the terminal is to use the virtual TTY. You can get into them by pressing Ctrl+Alt+F#. Read F# as one of the function keys from 1 to 7, for example. Probably, some of the initial combinations might be running your session manager or your graphical environment. The others will show a prompt asking for your login name like the one bellow:

arrelia in this case, is the hostname of the machine and tty3 is the terminal available after using the key combination above, plus the F3 key, like in Ctrl+Alt+F3.

After providing your login and password, you will finally get into a terminal, but there is no graphical environment in here, so, you won’t be able to use the mouse or run graphical applications without first starting an X, or Wayland, session. But that’s beyond the scope of this lesson.

The most important tool for presentations on Linux is LibreOffice Impress. It’s part of the open source office suite called LibreOffice. Think about LibreOffice as an open source replacement for the equivalent Microsoft Office. It can even open and save the PPT and PPTX files that are native to Powerpoint. But in spite of that, I really recommend you to use the native ODP Impress format. The ODP is part of the larger Open Document Format, which is a international standard for this kind of file. This is especially important if you want to keep your documents accessible for many years and worry less about compatibility problems. Because they are an open standard, it’s possible for anyone to implement the format without paying any royalties or licenses. This also makes you free to try other presentations software that you may like better and take your files with you, as it’s very likely they will be compatible with those newer softwares.

But if you prefer code over graphical interfaces, there are a few tools for you to choose. Beamer is a LaTeX class that can create slide presentations from LaTeX code. LaTeX itself is a typesetting system largely used for writing scientific documents at the academy, specially for its capacity to handle complex math symbols, which other softwares have difficulty to deal with. If you are at the university and need to deal with equations and other math related problems, Beamer can save you a lot of time.

The other option is Reveal.js, an awesome NPM package (NPM is the default NodeJS package manager) which allows you to create beautiful presentations by using the web. So, if you can write HTML and CSS, Reveal.js will bring most of the JavaScript necessary to create pretty and interactive presentations that will adapt well on any resolution and screen size.

Lastly, if you want a replacement for Microsoft Project, you can try GanttProject or ProjectLibre. Both are very similar to their proprietary counterpart and compatible with Project files.

Let’s assume you have browsed an e-commerce website, selected a product you wanted and placed that in the shopping cart. But at the last second, you have decided to give it a second thought and think a little longer if you really needed that. After a while, you start seeing ads of that same product following you around the web. When clicking on the ads, you are immediately sent to the product page of that store again. It’s not uncommon that the products you placed in the shopping cart are still there, just waiting for you to decide to check them out. Have you ever wondered how they do that? How they show you the right ad at another web page? The answer for these questions is called cookie tracking.

Cookies are small files a website can save on your computer in order to store and retrieve some kind of information that can be useful for your navigation. They have been in use for many years and are one of the oldest ways to store data on the client side. One good example of their use are unique shopping card IDs. That way, if you ever come back to the same website in a few days, the store can remember you the products you’ve placed in your cart during your last visit and save you the time to find them again.

That’s usually okay, since the website is offering you a useful feature and not sharing any data with third parties. But what about the ads that are shown to you while you surf on other web pages? That’s where the ad networks come in. Ad networks are companies that offer ads for e-commerce sites like the one in our example on one side, and monetization for websites, on the other side. Content creators like bloggers, for example, can make some space available for those ad networks on their blog, in exchange for a commission related to the sales generated by that ad.

But how do they know what product to show you? They usually do that by saving also a cookie from the ad network at the moment you visited or searched for a certain product on the e-commerce website. By doing that, the network is able to retrieve the information on that cookie wherever the network has ads, making the correlation with the products you were interested. This is usually one of the most common ways to track someone over the Internet. The example we gave above makes use of an e-commerce to make things more tangible, but social media platforms do the same with their “Like” or “Share” buttons and their social login.

One way you can get rid of that is by not allowing third party websites to store cookies on your browser. This way, only the website you visit can store their cookies. But be aware that some “legitimate” features may not work well if you do that, because many sites today rely on third party services to work. So, you can look for a cookie manager at your browser’s add-on repository in order to have a fine-grained control of which cookies are being stored on your machine.

Another common misconception is related to a certain browser configuration better known as DNT. That’s an acronym for “Do Not Track” and it can be turned on basically on any current browser. Similarly to the private mode, it’s not hard to find people that believe they will not be tracked if they have this configuration on. Unfortunately, that’s not always true. Currently, DNT is just a way for you to tell the websites you visit that you do not want them to track you. But, in fact, they are the ones who will decide if they will respect your choice or not. In other words, DNT is a way to opt-out from website tracking, but there is no guarantee on that choice.

Technically, this is done by simply sending an extra flag on the header of the HTTP request protocol (DNT: 1) upon requesting data from a web server. If you want to know more about this topic, the website https://allaboutdnt.com is good starting point.

You might have noticed the quotes in the heading above. This is because those windows are not as private as most people think. The names may vary but they can be called “private mode”, “incognito” or “anonymous” tab, depending on which browser you are using.

In Firefox, you can easily use it by pressing Ctrl+Shift+P keys. In Chrome, just press Ctrl+Shift+N. What it actually does is open a brand new session, which usually doesn’t share any configuration or data from your standard profile. When you close the private window, the browser will automatically delete all the data generated by that session, leaving no trace on the computer used. This means that no personal data, like history, passwords or cookies are stored on that computer.

Thus, many people misunderstand this concept by believing that they can browse anonymous on the Internet, which is not completely true. One thing that the privacy or incognito mode does is avoid what we call cookie tracking. When you visit a website, it can store a small file on your computer which may contain an ID that can be used to track you. Unless you configure your browser to not accept third-party cookies, ad networks or other companies can store and retrieve that ID and actually track your browsing across websites. But since the cookies stored on a private mode session are deleted right after you close that session, that information is forever lost.

Besides that, websites and other peers on the Internet can still use plenty other techniques in order to track you. So, private mode brings you some level of anonymity but it’s completely private only on the computer you are using. If you are accessing your email account or banking website from a public computer, like in an airport or a hotel, you should definitely access those using your browser’s private mode. In other situations, there can be benefits but you should know exactly what risks you are avoiding and which ones have no effect. Whenever you use a public accessible computer, be aware that other security threats such as malware or key loggers might exist. Be careful whenever you enter personal information, including usernames and passwords, on such computers or when you download or copy confidential data.

One of the most difficult situations any user faces is choosing a secure password for the services they make use of. You have certainly heard before that you should not use common combinations like qwerty, 123456 or 654321, nor easily guessable numbers like your (or a relative’s) birthday or zip code. The reason for that is because those are all very obvious combinations and the first attempts an invader will try in order to gain access to your account.

There are known techniques for creating a safe password. One of the most famous is making up a sentence which reminds you of that service and picking the first letters of each word. Let’s assume I want to create a good password for Facebook, for example. In this case, I could come up with a sentence like “I would be happy if I had a 1000 friends like Mike”. Pick the first letter of each word and the final password would be IwbhiIha1000flM. This would result in a 15 characters password which is long enough to be hard to guess and easy to remember at the same time (as long as I can remember the sentence and the “algorithm” for retrieving the password).

Sentences are usually easier to remember than the passwords but even this method has its limitations. We have to create passwords for so many services nowadays and as we use them with different frequencies, it will eventually be very difficult to remember all the sentences at the time we need them. So what can we do? You may answer that the wisest thing to do in this case is creating a couple good passwords and reuse them on similar services, right?

Unfortunately, that’s also not a good idea. You probably also heard you should not reuse the same password among different services. The problem of doing such a thing is that a specific service may leak your password (yes, it happens all the time) and any person who have access to it will try to use the same email and password combination on other popular services on the Internet in hope you have done exactly that: recycled passwords. And guess what? In case they are right you will end up having a problem not only on just one service but on several of them. And believe me, we tend to think it’s not going to happen to us until it’s too late.

So, what can we do in order to protect ourselves? One of the most secure approaches available today is using what is called a password manager. Password managers are a piece of software that will essentially store all your passwords and usernames in an encrypted format which can be decrypted by a master password. This way you only need to remember one good password since the manager will keep all the others safe for you.

KeePass is one of the most famous and feature rich open source password managers available. It will store your passwords in an encrypted file within your file system. The fact it’s open source is an important issue for this kind of software since it guarantees they will not make any use of your data because any developer can audit the code and know exactly how it works. This brings a level of transparency that’s impossible to reach with proprietary code. KeePass has ports for most operating systems, including Windows, Linux and macOS; as well as mobile ones like iOS and Android. It also includes a plugin system that is able to extend it’s functionality far beyond the defaults.

Bitwarden is another open source solution that has a similar approach but instead of storing your data in a file, it will make use of a cloud server. This way, it’s easier to keep all your devices synchronized and your passwords easily accessible through the web. Bitwarden is one of the few projects that will make not only the clients, but also the cloud server available as an open source software. This means you can host your own version of Bitwarden and make it available to anyone, like your family or your company employees. This will give you flexibility but also total control over how their passwords are stored and used.

One of the most important things to keep in mind when using a password manager is creating a random password for each different service since you will not need to remind them anyway. It would be worthless if you use a password manager to store recycled or easily guessable passwords. Thus, most of them will offer you a random password generator you can use to create those for you.

Transport Layer Security (TLS) is a protocol to offer security over network connections by making use of cryptography. TLS is the successor of the Secure Sockets Layer (SSL) which has been deprecated because of serious flaws. TLS has also evolved a couple of times in order to adapt itself and become more secure, thus it’s current version is 1.3. It can provide both privacy, and authenticity by making use of what is called symmetric and public-key cryptography. By saying that, we mean that once in use, you can be sure that nobody will be able to eavesdrop or alter your communication with that server during that session.

The most important lesson here is recognizing that a website is trustworthy. You should look for the “lock” symbol on the browser’s address bar. If you desire, you can click on it to inspect the certificate that plays an important role in the HTTPS protocol.

TLS is what is used on the HTTPS protocol (HTTP over TLS) in order to make it possible to send sensitive data (like your credit card number) through the web. Explaining how TLS works goes way beyond the purpose of this article, but you can find more information on the Wikipedia and at the Mozilla wiki.

There are plenty of tools for securing emails but one of the most important of them is certainly GnuPG. GnuPG stands for GNU Privacy Guard and it is an open source implementation of OpenPGP which is an international standard codified within RFC 4880.

GnuPG can be used to sign, encrypt, and decrypt texts, e-mails, files, directories, and even whole disk partitions. It works with public-key cryptography and is widely available. In a nutshell GnuPG creates a pair of files which contain your public and private keys. As the name implies, the public key can be available to anyone and the private key needs to be kept in secret. People will use your public key to encrypt data which only your private key will be able to decrypt.

You can also use your private key to sign any file or e-mail which can be validated against the corresponding public key. This digital signage works analogous to the real world signature. As long as you are the only one who posses your private key, the receiver can be sure that it was you who have authored it. By making use of the cryptographic hash functionality GnuPG will also guarantee no changes have been made after the signature because any changes to the content would invalidate the signature.

GnuPG is a very powerful tool and, in a certain extent, also a complex one. You can find more information on its website and on Archlinux wiki (Archlinux wiki is a very good source of information, even though you don’t use Archlinux).

A good way to secure your data is to encrypt your whole disk or partition. There are many open source softwares you can use to achieve such a purpose. How they work and what level of encryption they offer also varies significantly. There are basic two methods available: stacked and block device encryption.

Stacked filesystem solutions are implemented on top of existing filesystem. When using this method, the files and directories are encrypted before being stored on the filesystem and decrypted after reading them. This means the files are stored on the host filesystem in an encrypted form (meaning that their contents, and usually also their file/folder names, are replaced by random-looking data), but other than that, they still exist in that filesystem as they would without encryption, as normal files, symlinks, hardlinks, etc.

On the other hand, block device encryption happens below the filesystem layer, making sure everything that is written to a block device is encrypted. If you look to the block while it’s offline, it will look like a large section of random data and you won’t even be able to tell what type of filesystem is there without decrypting it first. This means you can’t tell what is a file or directory; how big they are and what kind of data it is, because metadata, directory structure and permissions are also encrypted.

Both methods have their own pros and cons. Among all the options available, you should take a look at dm-crypt, which is the de-facto standard for block encryption for Linux systems, since it’s native in the kernel. It can be used with LUKS (Linux Unified Key Setup) extension, which is a specification that implements a platform-independent standard for use with various tools.

If you want to try a stackable method, you should take a look at EncFS, which is probably the easiest way to secure data on Linux because it does not require root privileges to implement and it can work on an existing filesystem without modifications.

Finally, if you need to access data on various platforms, check out Veracrypt. It is the successor of a Truecrypt and allows the creation of encrypted media and files, which can be used on Linux as well as on macOS and Windows.