250 lines
12 KiB
Markdown
250 lines
12 KiB
Markdown
# Essential Linux
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## Introduction to Linux
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### Where does Linux originate from?
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* The spiritual mother of Linux is [Unix](https://en.wikipedia.org/wiki/Unix).
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* [POSIX](https://en.wikipedia.org/wiki/POSIX) is not an OS in itself but a **standard**.
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* Which OS's are [POSIX compliant](https://en.wikipedia.org/wiki/POSIX#POSIX-oriented_operating_systems)
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### Who is behind this project?
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* Who is [Richard Stallmann](https://en.wikipedia.org/wiki/Richard_Stallman)?
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* Who is [Linux Torvalds](https://en.wikipedia.org/wiki/Linus_Torvalds)?
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### What is the deal with 'GNU-slash-Linux'?
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* [GNU/Linux](https://en.wikipedia.org/wiki/GNU/Linux_naming_controversy) controversy
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* What is a [kernel](https://en.wikipedia.org/wiki/Kernel_(operating_system))
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* What does [GNU](https://www.gnu.org/software/) bring to the table?
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* What's the deal with [userspace and kernelspace](https://unix.stackexchange.com/questions/137820/whats-the-difference-of-the-userland-vs-the-kernel)?
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* [userspace](http://www.linfo.org/user_space.html)
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* [kernelspace](http://www.linfo.org/kernel_space.html)
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### Where can you *get* some Linux?
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* You probably already have a Linux computer running at [home](https://opensource.com/article/19/8/everyday-tech-runs-linux)!
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### Debian
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* [Reasons](https://www.debian.org/intro/why_debian) to choose Debian.
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* Why is Debian called [the universal operating system](https://www.reddit.com/r/debian/comments/22j0wf/so_why_debian_is_called_the_universal_operating/)?
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* [comparison](https://en.wikipedia.org/wiki/Comparison_of_instruction_set_architectures) of CPU architectures
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* [download](https://www.debian.org/distrib/netinst) Debian
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## How to create a virtual machine
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Step by step walk-through of a VM creation in virtualbox with some notes on each step with best practice pointers.
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## Breakdown of the Debian installation
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All right, enough talking, let's get started!
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I'll install a full blown and modern graphical Debian machine and I would like you to **not** do it yourself but take **notes** on each step so you'll be able to reference your notes later **when** I ask you to install a machine yourself.
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* [step by step](https://debian-handbook.info/browse/stable/sect.installation-steps.html) installation instructions
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* **don't set a root password, use `sudo` instead**
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* **stress the graphical/minimal difference**
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### Exercise
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OK, now it's up to you!
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Please install a Debian machine with the default graphical environment.
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Once installed, take some time out to explore the system.
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Which software is installed by default?
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How can you tweak the system settings such as language, keyboard, networking?
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Can you install extra software?
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## Quick look at an idle system
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## Package managers
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* what is a [package manager](https://en.wikipedia.org/wiki/Package_manager)
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### Graphical installation
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### Command line installation
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```bash
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waldek@hellodebian:~$ htop
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-bash: htop: command not found
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waldek@hellodebian:~$ apt install htop
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E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
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E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
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waldek@hellodebian:~$ sudo apt install htop
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[sudo] password for waldek:
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Reading package lists... Done
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Building dependency tree... Done
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Reading state information... Done
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Suggested packages:
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lm-sensors strace
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The following NEW packages will be installed:
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htop
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0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
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Need to get 127 kB of archives.
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After this operation, 328 kB of additional disk space will be used.
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Get:1 http://deb.debian.org/debian bullseye/main amd64 htop amd64 3.0.5-7 [127 kB]
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Fetched 127 kB in 0s (2,030 kB/s)
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Selecting previously unselected package htop.
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(Reading database ... 141359 files and directories currently installed.)
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Preparing to unpack .../htop_3.0.5-7_amd64.deb ...
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Unpacking htop (3.0.5-7) ...
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Setting up htop (3.0.5-7) ...
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Processing triggers for mailcap (3.69) ...
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Processing triggers for desktop-file-utils (0.26-1) ...
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Processing triggers for hicolor-icon-theme (0.17-2) ...
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Processing triggers for gnome-menus (3.36.0-1) ...
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Processing triggers for man-db (2.9.4-2) ...
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waldek@hellodebian:~$
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```
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The *menu bar* at the bottom shows you can press **F10** to quit.
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This does not work because of a shortcut of gnome-terminal!
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You can deactivate this shortcut in the preferences though.
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But pressing **q** also exits the program.
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### Adding a secondary desktop environment
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During the initial installation we where offered a choice of desktop environments to install.
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This menu was an actual program called `tasksel` we can run again to add different ones!
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As it's a program that can heavily modify the system, we need administrator privileges.
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```bash
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waldek@hellodebian:~$ sudo tasksel
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[sudo] password for waldek:
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```
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## Changing the runlevel
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The **first** process started by the kernel can be discover by `htop` and is `/usr/sbin/init`.
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This is rather vague but we can find out a *bit* more about this program via `ls` which we'll get into more detail later.
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For now just have a look at the output of the following commmand.
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```bash
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waldek@hellodebian:~$ ls -l /usr/sbin/init
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lrwxrwxrwx 1 root root 20 Jul 13 2021 /usr/sbin/init -> /lib/systemd/systemd
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waldek@hellodebian:~$
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```
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Now, what *is* this [systemd](https://en.wikipedia.org/wiki/Systemd)?
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And more importantly, *how* do we interact with it?
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For now just accept that the main program to communicate with `systemd` is `systemctl`.
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A quick look at the `man` pages gives us the following.
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```bash
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SYSTEMCTL(1) systemctl SYSTEMCTL(1)
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NAME
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systemctl - Control the systemd system and service manager
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SYNOPSIS
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systemctl [OPTIONS...] COMMAND [UNIT...]
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DESCRIPTION
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systemctl may be used to introspect and control the state of the "systemd" system and service manager. Please refer to systemd(1) for an
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introduction into the basic concepts and functionality this tool manages.
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```
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```bash
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waldek@hellodebian:~$ sudo systemctl set-default multi-user.target
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[sudo] password for waldek:
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Removed /etc/systemd/system/default.target.
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Created symlink /etc/systemd/system/default.target → /lib/systemd/system/multi-user.target.
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waldek@hellodebian:~$ sudo reboot now
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```
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After the reboot you'll be confronted with the following screen.
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Don't stress, your machine is not broken!
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It's just running in a more *minimal* mode.
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You can log in just as with the graphical login window but you'll only have a command line to interact with the machine.
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A quick look at `htop` tells us not a lot of stuff is running, just the bare minimum.
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To *undo* this change and regain the graphical interface again you can run the following commands.
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```bash
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waldek@hellodebian:~$ sudo systemctl set-default graphical.target
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[sudo] password for waldek:
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Removed /etc/systemd/system/default.target.
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Created symlink /etc/systemd/system/default.target → /lib/systemd/system/graphical.target.
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waldek@hellodebian:~$ sudo reboot now
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```
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## Exercise
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Please create a second virtual machine and install a **minimal** Debian.
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Minimal means **no graphical environment**.
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I advise you to **not** set a root password.
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Once this machine is up and running, install a few programs.
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The only one we saw up until now is `htop` but maybe try out `bmon`, `elinks` and/or `ranger`.
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