335 lines
15 KiB
Markdown
335 lines
15 KiB
Markdown
# Linux Primer
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My packet radio guide is focussed on running software on Linux and it probably
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assumes a base level of knowledge. I shall dispense some thoughts and you can
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judge whether this is helpful.
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!!! note
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For those of you with greater background knowledge and opinions, you'll notice I'm painting in broad brushstrokes. This is intentional, don't bite my head off!
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## What is Linux?
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Linux is, in general terms, a family of operating systems that share a common
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core set of software and exhibit similar characteristics. It is no one simple
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thing, and doesn't fit in one neat category.
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It can be seen as an alternative to Windows, MacOS, DOS, FreeBSD etc on the
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desktop - there are many similarities and many differences.
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It is built collaboratively by enthusiast and professional software developers
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in the spirit of freely sharing and improving the world for all humans - in
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this sense, there is a strong overlap with the goals of man radio amateurs.
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Through this guide I will regularly refer to "[Debian](https://debian.org)" -
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this is the 'Distribution' of Linux that I work on in my free time. A
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distribution is a collection of software maintained by a group of people. In
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the case of Debian, there's around 1000 of us working on it.
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As the source code is available for all to see and use due to permissive
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licenses, if another group has an opinion which differs from the team producing
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a distribution, they can use our work as a foundation and build something
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different and new based on that - we call this 'forking'. This is what
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[Ubuntu](https://ubuntu.com) is, and why we refer to Ubuntu as a 'Debian
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Derivative'. It's also why 90% of tutorials that target Ubuntu will work for
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Debian and vice versa. We share common components and building blocks.
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Raspberry Pi OS falls into this category too - they are standing on Debian's
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shoulders and commonly re-base their system on ours, so that they can focus
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their efforts on making the Raspberry Pi work well instead of getting bogged
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down in every tangential detail.
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An alternative to Debian and its derivatives is
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[Fedora](https://www.fedoraproject.org) - while this shares many common
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components and code at the core of the system, some of the tools used in Fedora
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differ to such an extent that software built for it can't be guaranteed to run
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on a Debian based system - similar to Mac vs Windows.
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There are hundreds, if not thousands, of Linux Distributions all with different
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goals. Some are derivatives focussed on a specific task, some are very General
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and left to you to configure and use. Some are even delivered as code and you
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need to compile it from the ground up.
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## Desktops and Terminals
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There's a common misconception that Linux is for command line users only, or
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that you need to be proficient in the command line to be able to drive it. This
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is no more true in Linux than it is for MacOS and Windows - there are a number
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of tasks that some may find more efficient to do via the command line interface
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(CLI), but there are usually multiple ways to skin the cat.
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Much of my advice will take the form of things to run in the command line, as
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this is often the way I interact with my computers, but I am endeavouring to
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diversify so things are more approachable.
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If you're running the Raspberry Pi, it's most likely you have [Raspberry Pi
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OS](https://www.raspberrypi.com/software/) with a desktop - there'll be a
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background, a menu in the top left etc. It might not look familiar, but to a
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keen explorer it should look approachable at the very least.
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If you're running Debian, during install we'll ask you what graphical desktop
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environment you want to install, if any. This is the desktop you boot in to -
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unlike Windows, there are multiples available for Linux. As a beginner, I
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strongly recommend [KDE](https://kde.org) Plasma - it is quite Windows like and
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is pretty full featured. If you're running Ubuntu, typically you install an
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Ubuntu derivative focussed on a specific desktop environment - perhaps
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[Kubuntu](https://kubuntu.org) for KDE.
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## Applications and Repositories
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Most Linux distributions are not only just the system and the desktop, but they
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are shipped with a vast catalogue of applications too. They might not be
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installed, and you'll need to use some sort of app store tool to install, remove
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etc applications. It's just like every modern mobile phone - they stole the idea
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from us!
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We call this tool a package manager (we often call applications 'packages'), and
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a collection of applications is known as a repository, or repo. The Debian
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family use a program called `apt` as its package manager, and it ships with
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quite a large repository of apps you can choose from. Most guides, mine
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included, don't focus on showing you a usable app-store, just a method of
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installing from a repository.
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You might want to add another repository if to get access to additional
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software, new software that isn't shipped by the distribution's maintainers or
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some other reason. I keep more up to date versions of software in my repository
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than Raspberry Pi OS offers, and I have additional software that isn't offered
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by RasPi OS too.
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### Install from the Command Line
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To install from the command line, the standard command would be:
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!!! note "Terminal Command
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`apt install x`
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Where x is any application you're looking for. This is often prefixed with
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`sudo`, see below in [Users, Permissions and sudo](linux.md/#users-permissions-and-sudo) to learn more about why.
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### Graphical App Store Frontend
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Instead of using `apt install x`, it is possible to run a graphical piece of
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software.
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#### Raspberry Pi
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The Raspberry Pi ships with a GUI through which you can install packages. It
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lives in the Raspberry Pi menu (top left, Raspberry Pi icon), Preferences,
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Add/Remove software.
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#### Other systems
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Have a little look through your application launcher menu to see if there is an
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app catalogue, application store, package list or similar. If nothing is there,
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then you might need to look to install something. In KDE this is called 'Discover'.
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One I recommend is 'Synaptic' - you might have it installed already, or you
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might have to quickly run the below to get it
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!!! note "Terminal Command"
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`apt install synaptic`
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On the Raspberry Pi, it's as below. To find it, go to the Raspberry Pi menu (Raspberry Icon, Top Left), Preferences and select Add/Remove software.
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## Filesystem Layout
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In a Windows system, the very top of your computer's filesystem is most often the C Drive, represented as C: commonly. Windows also neatly shows other drives as similar folder structures - CD Drives often start at D:, Floppy drives at A:.
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In Linux we follow a different filesystem hierarchy, starting at the 'root' of the drive, commonly labelled as `/`. Everything else on the system is presented as a file or a folder under `/`. This includes CD Roms, Hard drives which present as folders, serial & USB devices which present as files and more.
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Paths always start with a `/`, and if it's a folder it will end with a `/` to indicate there is more depth below.
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Devices, as they present, are often named by the class of device and a number
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starting at 0 to indicate which number it is. You'll commonly see references to
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`eth0`, showing the first Ethernet device or `wlan0` showing the first wireless
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internet adaptor. A second would be `wlan1` etc.
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If I look at my root filesystem, I see the following folders:
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```
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❯ ls /
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bin@ dev/ home/ lost+found/ mnt/ proc/ run/ srv/ tmp/ var/
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boot/ etc/ lib@ media/ opt/ root/ sbin@ sys/ usr/
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```
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!!! tip
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I used `ls` here to list the folders in the terminal, but the DOS classic `dir` will also work!
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Many folders won't be of interest to you day to day, but some helpful ones to know are:
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* `/dev/` - A folder containing devices, it's likely your modem appears here as `/dev/ttyACM0`
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* `/etc/` - This folder contains every system configuration file, and you could think of it as similar to the Windows Registry.
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* `/home/` - The home folder is the equivalent to `C:\Users\` on Windows. `/home/hibby/` is where my files live, just like `C:\Users\Hibby`
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* `/mnt/` - Often where hard drives appear as a folder. A CD Drive called `D:\` on Windows might appear as `/mnt/cdrom/` here.
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* `/tmp/` - A handy scratchpad to test and download things to. It gets emptied on every reboot
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## Users, Permissions and 'sudo'
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Much like other systems, Linux has the concept of a regular 'user' which you
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log in as, day to day and an 'administrator' user who is empowered to make
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configuration changes to the system, install software and so on. In the Linux
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world, the administrator is known as 'root'. As root has a lot of power -
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changing users passwords, deleting every file, overriding safe norms to damage
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hardware potentially - it is generally recommended that you do not log in day
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to day as root. If a bad actor or malicious piece of software runs while you
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are root, it can cause all of the aforementioned damage and more!
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Again, similar to windows, you can run a command as the root user, effectively
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temporarily granting access to just one program to perform a specific task. In
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Windows, what usually happens is a pop up window appears asking if you want to
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do that and pressing yes or no. In Linux, we will have configured the system in
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advance to know that your user is allowed to do this, and then it will ask for
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your password to grant permission to carry out the action.
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In graphical environments this may take the form of a pop up window - more
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often than not, however, we do this from the command line by prefixing our
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whole command with `sudo` - you can see a lot of examples of `sudo` in use at
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[the repo page](repo.md).
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Looking at the repo as an example and considering our earlier learning from
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Applications and Repositories above - it's no wonder that you need to carry out
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the commands mostly as the root user! To add my repository, you are making a
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major system configuration change in two manners:
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* Telling it to trust absolutely the software that I distribute
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* Telling the package manager where to download that software from
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From this point on, you're placing a lot of trust in me personally - I can make
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quite significant changes to your system, or open up security holes, or
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accidentally break programs. I promise to not abuse this trust - to do so would
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break our Social Contract, result in me being ejected from several communities
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I love and I'd probably have to find a new set of hobbies.
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You can, of course, revoke this decision at any point by removing the repo key
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and entry in `/etc/apt.conf`.
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### How do I know if I can run programs as root?
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This is one for the command line! I recommend running groups:
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!!! note "Terminal Command"
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`groups`
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The output on my system looks like:
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```
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❯ groups
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hibby cdrom floppy sudo audio dip video plugdev users netdev lpadmin scanner sbuild
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```
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You can see in my group list that I can access the cd rom drive, the floppy
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drive and run things as sudo, amongst other less important groups!
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If you do *not* have sudo in this list, you'll need a bit more help than I can
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give here - time to [ask for help!](beginners-guide.md#ask-for-help). If you're
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running a Raspberry Pi or Ubuntu, chances are that you'll be able to. Debian is
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a little more paranoid so we don't grant it by default.
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You'll need to run a command called `usermod` as the root user to grant your regular user a new group -
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!!! note "Terminal Command"
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`usermod -aG <groupname> <username>`
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This effectively translates to 'add <username> to <groupname>. Get rid of the
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brackets and add the user and group you're trying for! See [Permissions and
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Groups](#Permissions-and-Groups) for an example.
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### Editing text as root
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The path of least resistance for many is to use the command line - if you know
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what file you need to edit, you can do that quickly and directly using a
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command line text editor.
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The GUI offers some choices - my preferred method is below.
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##### GUI
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I recommend installing Featherpad for this - it's lightweight and will only ask
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for a password when you save the file.
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If you use the KDE Desktop, Kate works and has the below functionality inbuilt.
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To install it see [above](linux.md/#graphical-app-store-frontend) for more.
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You can open Featherpad from the application launcher and use the file->open
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menu to get access to files all round the system:
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Take yourself back to `/` with the Path breadcrumb at the top, and to edit the
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bpq32.conf config file, for example, find `/etc/bpq32.cfg`.
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On saving the file, the system will ask you to enter your password as it's a
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protected file that only the root user can write to:
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Alternatively, after installing featherpad you can open your file manager,
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navigate to `/etc/`, open `bpq32.cfg` and the system will present a similar
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popup when you try to save:
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In all these programs, you can find `/etc/` by typing `/etc` in the navigation
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bar that is top-central, or by Pressing 'Filesystem Root' on the left hand side
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and navigating to etc in the main pane.
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#### Command Line
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Every Debian system ships with a text editor called `nano` which is relatively approachable.
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You open your file directly, so to edit the BPQ config file, run:
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!!! note "Terminal Command"
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`sudo nano /etc/bpq32.cfg`
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This translates to: `As root user, open nano to edit /etc/bpq32.cfg`
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Navigation is with arrow keys (no mouse, sorry!). There are a list of commands
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at the bottom of the screen - they use ^ as a shortcut to indicate you must
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press control at the same time as those letters. Similarly, M is an indication
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of 'meta' key, which will likely be the alt key. This is quite similar to
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keyboard shortcuts in Microsoft Word (ctrl&s for save, alt-f4 for exit).
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Some helpful commands to know:
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| Command | Action |
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| ------- | ------ |
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| ctrl & o | Save |
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| ctrl & x | Exit |
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| ctrl & w | Find (helpful for quick navigation) |
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| alt & u | Undo |
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| alt & e | Redo |
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| ctrl & k | Cut Line |
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| ctrl & u | Paste Line |
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### Permissions and Groups
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Files, devices and folders can have read and write permissions tied to both a
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user and a group, just as in Windows. You can check this in your file manager
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by right clicking and selecting properties.
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In the command line, this can be checked also - to understand who can do what
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with a NinoTNC, plug it in and run
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!!! note "Terminal Command"
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`ls -l /dev/ttyACM0`
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The output on my system looks like:
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```
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❯ ls -l /dev/ttyACM0
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crw-rw---- 1 root dialout 204, 64 Apr 11 08:32 /dev/ttyACM0
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```
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This can be read as the device is owned by root and accessible by the group
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`dialout`. This is a common group you'll see regularly for serial devices, and
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worth being a member of. If a device has dialout as its group, this is telling
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us unless your user is root or in the dialout group, you cannot use the device.
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To add your user to the dialout group, you may need to run the usermod command
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as mentioned above. To add my user hibby, it would be
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!!! note "Terminal Command"
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`usermod -aG dialout hibby`
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!!! tip
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As this command needs to be run as the root user, we probably need to run `sudo usermod -aG dialout hibby`
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For this change to take effect, you will need to log out and log in again.
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