1132 lines
79 KiB
Markdown
1132 lines
79 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 [Linus 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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In order to run virtual machines, or VM's, we need a **host** program.
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One of the most popular ones out there is called `virtualbox`.
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It should be installed on your machine but in case it's not you can download it [here](https://www.virtualbox.org/wiki/Downloads).
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If you **expand** the section below you'll see a 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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<details>
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<summary>Expand me...</summary>
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**Nice!**
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1. Name your machine and select *linux* if it's not chosen automatically.
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1. Set the amount of RAM for your machine.
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This can be anything between an absolute minimum and your physical machine's limit.
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You can't *magically* use more RAM than physically available!
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1. You need a virtual hard drive to store the OS and all your data to.
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1. The format doesn't matter that much.
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I always go for the default one.
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1. Most of the time you'll want dynamic size meaning the disk **file** will only take up as much **space** as it needs.
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For example, if you set a size of 50GB for your disk and your OS plus personal files take up 12GB, the actual space this image takes op on the physical disk of your **host** will be about 12GB.
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1. We'll soon discover **how much space** a basic Linux installation takes up but for now I would recommend the following.
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* **with** a graphical environment: 20GB
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* **without** a graphical environment: 10GB (minimal/server/headless install)
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1. By default your machine will have only **one** CPU core but you can add more via the settings.
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This is something you can change whenever you need more processing power but the same rule as with the RAM applies, it's not a magical way to add resources to your machine.
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1. Last but not least we need to insert the installation disk into the virtual machine and boot it up!
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</details>
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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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Below is a gain a step by step walk through with some of my tips but a more details guide can be found in the [Debian Administrator Handbook](https://debian-handbook.info/browse/stable/sect.installation-steps.html).
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This book is a real *bible* of information and I highly advise you to read through it.
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My most important notes would be the following.
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* **Read** each section carefully and you'll know what to do.
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* Don't set a root password but use `sudo` instead.
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* Don't install a graphical environment if you don't need one.
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It's a lot easier to add one later than to remove it.
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* Don't forget to install `grub` at the end otherwise your installation will not be able to boot.
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You *can* recover from this mistake with [supergrub2](https://www.supergrubdisk.org/super-grub2-disk/) but that's for an other day.
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<details>
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<summary>Expand me...</summary>
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</details>
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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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You can inspect the system by running the *gnome task manager*.
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It lists all your running processes, sorted by CPU percentage, in the first tab which can give you a good idea of what's happening on your system.
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Note that an idle system uses almost **no resources**!
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Plus, a fresh install, with quite a few essential programs such as a browser, music player, text editor, etc only takes up about 5GB of disk space!
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This is mind blowing compared to a windows installation.
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How is this possible?
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That's the magic of a good package manager!
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<details>
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<summary>Expand me...</summary>
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</details>
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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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Modern Linux has come a long way and it's now quite usable without any command line knowledge.
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We can install extra software from the graphical environment if we want.
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Let's look for `vlc`, a popular open source video player.
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When we look for it from `activities` we *see* a reference to it via the `software` program.
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If we click on it we'll be take to a sort of *app or play store* where we can choose to install or uninstall programs.
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Because adding and removing software from our machine is quite *invasive*, we need to **prove** we have the right to do so.
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A prompt will pop up where you'll need to input **your** password.
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If your password does not work, you probably set a `root` password and you should use that one instead.
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<details>
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<summary>Expand me...</summary>
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</details>
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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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Once these are installed have a look at the running services and programs via `htop` and compare it to both your graphical installation **and** your graphical install but running in `multi-user.target`.
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## Guest additions
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Let's make our user experience a bit nicer.
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Virtual machines can *integrate* with the host machine more fluently when you install the guest additions in the VM.
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It's a three step process.
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1. install the required packages to build the guest additions in you VM
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1. insert the guest additions CD into your VM
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1. run the correct script from the CD
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The dependencies can be installed as follows.
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First you `update` your package list, next you install three packages.
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* `build-essential`
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* `dkms`
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* `linux-headers-$(uname -r)`
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The *third* package name is a bit weird looking no?
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This is a bit of command line kung fu.
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The actual *name* of the package is as follows.
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```
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waldek@hellodebian:~$ echo linux-headers-$(uname -r)
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linux-headers-5.10.0-11-amd64
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waldek@hellodebian:~$
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```
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The `$(uname -r)` is a call to a program called `uname` with the option `-r`.
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We'll go more into detail on this later.
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```
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waldek@hellodebian:~$ sudo apt update
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Hit:1 http://deb.debian.org/debian bullseye InRelease
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Hit:2 http://deb.debian.org/debian bullseye-updates InRelease
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Hit:3 http://security.debian.org/debian-security bullseye-security InRelease
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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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All packages are up to date.
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waldek@hellodebian:~$ sudo apt install build-essential dkms linux-headers-$(uname -r)
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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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The following additional packages will be installed:
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binutils binutils-common binutils-x86-64-linux-gnu dctrl-tools dpkg-dev fakeroot g++ g++-10 gcc gcc-10 libalgorithm-diff-perl
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libalgorithm-diff-xs-perl libalgorithm-merge-perl libasan6 libatomic1 libbinutils libc-dev-bin libc-devtools libc6-dev libcc1-0 libcrypt-dev
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libctf-nobfd0 libctf0 libfakeroot libgcc-10-dev libitm1 liblsan0 libnsl-dev libstdc++-10-dev libtirpc-dev libtsan0 libubsan1
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linux-compiler-gcc-10-x86 linux-headers-5.10.0-11-common linux-headers-amd64 linux-kbuild-5.10 linux-libc-dev make manpages-dev patch
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Suggested packages:
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binutils-doc debtags debian-keyring g++-multilib g++-10-multilib gcc-10-doc gcc-multilib autoconf automake libtool flex bison gdb gcc-doc
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gcc-10-multilib gcc-10-locales glibc-doc libstdc++-10-doc make-doc ed diffutils-doc
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The following NEW packages will be installed:
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binutils binutils-common binutils-x86-64-linux-gnu build-essential dctrl-tools dkms dpkg-dev fakeroot g++ g++-10 gcc gcc-10 libalgorithm-diff-perl
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libalgorithm-diff-xs-perl libalgorithm-merge-perl libasan6 libatomic1 libbinutils libc-dev-bin libc-devtools libc6-dev libcc1-0 libcrypt-dev
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libctf-nobfd0 libctf0 libfakeroot libgcc-10-dev libitm1 liblsan0 libnsl-dev libstdc++-10-dev libtirpc-dev libtsan0 libubsan1
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linux-compiler-gcc-10-x86 linux-headers-5.10.0-11-amd64 linux-headers-5.10.0-11-common linux-headers-amd64 linux-kbuild-5.10 linux-libc-dev make
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manpages-dev patch
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0 upgraded, 43 newly installed, 0 to remove and 0 not upgraded.
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Need to get 62.0 MB of archives.
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After this operation, 258 MB of additional disk space will be used.
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Do you want to continue? [Y/n] y
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```
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Once this is done we can **insert** the CD.
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You can verify the disk's content via the files explorer in gnome.
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Now, open a terminal and run the following.
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```
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waldek@hellodebian:~$ cd /media/cdrom0/
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waldek@hellodebian:/media/cdrom0$ ls
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AUTORUN.INF NT3x TRANS.TBL VBoxLinuxAdditions.run VBoxWindowsAdditions.exe
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autorun.sh OS2 VBoxDarwinAdditions.pkg VBoxSolarisAdditions.pkg VBoxWindowsAdditions-x86.exe
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cert runasroot.sh VBoxDarwinAdditionsUninstall.tool VBoxWindowsAdditions-amd64.exe
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waldek@hellodebian:/media/cdrom0$ sudo bash VBoxLinuxAdditions.run
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Verifying archive integrity... All good.
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Uncompressing VirtualBox 6.1.28 Guest Additions for Linux........
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VirtualBox Guest Additions installer
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Copying additional installer modules ...
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Installing additional modules ...
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VirtualBox Guest Additions: Starting.
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VirtualBox Guest Additions: Building the VirtualBox Guest Additions kernel
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modules. This may take a while.
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VirtualBox Guest Additions: To build modules for other installed kernels, run
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VirtualBox Guest Additions: /sbin/rcvboxadd quicksetup <version>
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VirtualBox Guest Additions: or
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VirtualBox Guest Additions: /sbin/rcvboxadd quicksetup all
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VirtualBox Guest Additions: Building the modules for kernel 5.10.0-11-amd64.
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update-initramfs: Generating /boot/initrd.img-5.10.0-11-amd64
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VirtualBox Guest Additions: Running kernel modules will not be replaced until
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the system is restarted
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waldek@hellodebian:/media/cdrom0$ sudo reboot now
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```
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Once the machine is rebooted you'll can resize the window and the screen resolution will adapt automatically!
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You can also enable copy/paste and drag and drop between your host and VM now.
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## Introduction to the command line
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We'll be using a few new *words* to reference the command line such as *shell*, *bash* and *terminal* through out the course.
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They all pretty much mean the same thing but with some small, and not so important, differences between them.
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Essentially a command line is a **textual interface** for humans to operate a computer.
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What is very important to understand is that textual commands and graphical actions operate on the **same** computer.
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For example, if you create a file via the command line, it will show up in you file explorer and vice versa.
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The graphical and textual interfaces are just different *representations* of the same machine.
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Now open up a terminal and you'll see the following.
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```
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waldek@hellodebian:~$
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```
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This is what we call a [prompt](https://en.wikipedia.org/wiki/Command-line_interface#Command_prompt).
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It's not much but it's our *window* into the computer.
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As with most things in life you can question it's *who, where, what and when*.
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This information is actually **embedded** in the prompt.
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Let's break it down.
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* `waldek` is **who** I am on this computer
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* `hellodebian` is the **what**, as in what computer I'm operating on
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* `~` is **where** I am located on this computer
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What about the *when* then?
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Let's type in `date` and see what happens.
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```
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waldek@hellodebian:~$ date
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Fri 18 Feb 2022 03:46:59 PM CET
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waldek@hellodebian:~$
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```
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There we see our **when**!
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But this miniscule operation illustrates us the **fundamental** operation of a command line!
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1. we have a prompt where we can run a program
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2. the program runs and outputs it's information on the terminal
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3. once the program **finishes** we can run an other program
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I'm deliberately saying program here but is `date` *really* a program?
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It's a bit basic no?
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Well, it is a program and most *commands* you'll type into your terminal are actually programs.
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We can illustrate this as follows.
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```
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waldek@hellodebian:~$ vlc
|
||
VLC media player 3.0.16 Vetinari (revision 3.0.13-8-g41878ff4f2)
|
||
[0000559c46ee95b0] main libvlc: Running vlc with the default interface. Use 'cvlc' to use vlc without interface.
|
||
[0000559c46f89790] main playlist: playlist is empty
|
||
|
||
```
|
||
|
||
Vlc is now running and the terminal is *blocked* meaning we can't run other programs or commands in it.
|
||
If you try to run the `date` command again, or `ls` or `htop`, it won't work!
|
||
Try it out if you don't believe me.
|
||
But what happens if you **close** vlc?
|
||
The commands you typed get executed!
|
||
This is an illustration of the **sequential** nature of a command line.
|
||
|
||
Now, I don't think we have sufficiently *proven* that `date` is a full blown program so let's dig a bit deeper.
|
||
|
||
```
|
||
waldek@hellodebian:~$ which vlc
|
||
/usr/bin/vlc
|
||
waldek@hellodebian:~$ which date
|
||
/usr/bin/date
|
||
waldek@hellodebian:~$ which which
|
||
/usr/bin/which
|
||
```
|
||
|
||
There is quite bit to *unpack* in the example above.
|
||
First, what on earth is `which`?
|
||
Well, it's *also* a program and it's sole purpose in life is to tell you **where** a program is located on your system.
|
||
Because `which` by itself does not make a lot of sense it needs what we call an **argument**.
|
||
Here the argument is the name of the program we want to know it's location of.
|
||
The existence of arguments is the second big thing we discovered here.
|
||
The third new thing we can observe here is what we call **paths**, meaning locations on the system.
|
||
For example, `vlc` is a *binary* program located in a **folder** called `bin` which is located in a folder called `usr` which is at the *root* of your system.
|
||
If this sounds complicated, don't worry, we'll go into detail a bit later.
|
||
|
||
Now that we know **where** some of our programs are located, let's find out **what** they are.
|
||
The methodology is the same as with `which` but we'll use an other program called `file` who's purpose in life is to tell more about the **content** of a certain file.
|
||
Logically, `file` needs an argument and this argument is the **path** to the file you want to inspect.
|
||
|
||
```
|
||
waldek@hellodebian:~$ file /usr/bin/vlc
|
||
/usr/bin/vlc: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=51c40f8234213415771b3a344cab25a140543f8a, for GNU/Linux 3.2.0, stripped
|
||
waldek@hellodebian:~$ file /usr/bin/date
|
||
/usr/bin/date: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=b740f054aaef6a85aff024858c914c7eae70a6a5, for GNU/Linux 3.2.0, stripped
|
||
waldek@hellodebian:~$ file /usr/bin/which
|
||
/usr/bin/which: POSIX shell script, ASCII text executable
|
||
waldek@hellodebian:~$ file $(which which) # this is some command line kung fu...
|
||
/usr/bin/which: POSIX shell script, ASCII text executable
|
||
waldek@hellodebian:~$
|
||
```
|
||
|
||
Here we learn that both `vlc` and `date` are **executables**, compiled for an x86-64 system.
|
||
I would say they are both created *equally* no?
|
||
Both are actual programs.
|
||
But what about `which`?
|
||
It's also an executable but not compiled, it's a *POSIX shell script*.
|
||
So not all programs *are* created equally?
|
||
|
||
### Compiled vs interpreted
|
||
|
||
Executing a file, or program, means you take this file and tell the computer it needs to execute the actions that are stored in the file.
|
||
Compiled programs contain actual [instructions](https://en.wikipedia.org/wiki/Instruction_set_architecture#Instructions) the computer understands out of the box.
|
||
This means that programs that are compiled are always compiled for a specify architecture which in our case is x86-64.
|
||
On a Raspberry Pi this would be armhf or arm64.
|
||
|
||
Interpreted programs are not compiled to machine code but when we run them each line is passed to an appropriate **interpreter** and executed **line by line**.
|
||
The first line of a script is often the path to the interpreter that *understands* the code that will follow.
|
||
Popular interpreted languages are `bash`, `sh`, `python`, `php`, ...
|
||
|
||
We can take it *one* more step forward and peak into the *content* of the files.
|
||
A nice little program to do this is called `head` who's purpose in life is to show the first few lines of a file.
|
||
First for `vlc`.
|
||
|
||
```
|
||
waldek@hellodebian:~$ head /usr/bin/vlc
|
||
ELF>@<40>1@8
|
||
HHh,h<h<<3C><><EFBFBD>,<2C><<3C>< <20><><EFBFBD>DDP<44>td###<23><>Q<EFBFBD>tdR<64>tdh,h<h<<3C><>/lib64/ld-linux-x86-64.so.2GNUQ<EFBFBD><EFBFBD>4!4w4L<34>%<25>@T?<3F>GNU)<29>)*<2A>e<EFBFBD>m9<6D>y<EFBFBD><79><EFBFBD><EFBFBD> <20><>)F <20>, X<>`
|
||
Pco<EFBFBD><EFBFBD><EFBFBD><EFBFBD>v<EFBFBD><EFBFBD>ZD<EFBFBD>
|
||
<20><>/<2F><><EFBFBD>h<EFBFBD>"<22> _ITM_deregisterTMCloneTable__gmon_start___ITM_registerTMCloneTablelibvlc_set_app_idlibvlc_newlibvlc_set_user_agentlibvlc_get_changesetlibvlc_get_versionlibvlc_set_exit_handlerlibvlc_add_intflibvlc_playlist_playlibvlc_releasesigwaitflockfilepthread_killpthread_sigmaskpthread_mutex_lockpthread_mutex_unlockfunlockfilesigactiondlsymdlerrorfflushsignal__stack_chk_failabortisattysigemptysetrand_r__fprintf_chksigaddsetmemcpystderrsigdelsetalarmfwritegeteuid__vfprintf_chk__cxa_finalizepthread_self__libc_start_main__register_atforklibvlc.so.5libpthread.so.0libdl.so.2libc.so.6GLIBC_2<EFBFBD>ri5GLIB<EFBFBD>ti.14GL<EFBFBD>u<EFBFBD>i2.4Glh<EFBFBD>p<EFBFBD>@<40>?<3F>?GLIBC_2.3.G u<>i lW u<>i lb<6C><62>xii
|
||
<EFBFBD>?
|
||
<20>?<3F>?) @*<2A>><3E>><3E>><3E>><3E>><3E>><3E><>> <09>>
|
||
??? ?(?0?8?@?H?P?X?`?<3F>h??x?<3F>?<3F>?<3F>? <20>?!<21>?"<22>?#<23>?$<24>?%<25>?&<26>?'<27>?(H<>H<EFBFBD><48>/H<><48>t<EFBFBD><74>H<EFBFBD><48><EFBFBD>5<EFBFBD>.<2E>%<25>.@<40>%<25>.h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%z.h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%r.h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%j.h<><68><EFBFBD><EFBFBD><EFBFBD>%b.h<><68><EFBFBD><EFBFBD><EFBFBD>%Z.h<><68><EFBFBD><EFBFBD><EFBFBD>%R.h<><68><EFBFBD><EFBFBD><EFBFBD>%J.h<>p<EFBFBD><70><EFBFBD><EFBFBD>%B.<2E>`<60><><EFBFBD><EFBFBD>%:.h <09>P<EFBFBD><50><EFBFBD><EFBFBD>%2.h
|
||
<EFBFBD>@<40><><EFBFBD><EFBFBD>%*.h
|
||
<20>0<EFBFBD><30><EFBFBD><EFBFBD>%".h
|
||
<EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%.h<><68><EFBFBD><EFBFBD><EFBFBD>% <20> <20><><EFBFBD><EFBFBD>%<25>.h
|
||
.h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%.h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD>%<25>-h<>p<EFBFBD><70><EFBFBD><EFBFBD>%<25>-h<>`<60><><EFBFBD><EFBFBD>%<25>-h<>P<EFBFBD><50><EFBFBD><EFBFBD>%<25>-h<><68>@<40><><EFBFBD><EFBFBD>%<25>-h0<68><30><EFBFBD><EFBFBD>%<25>-h<> <20><><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD>%<25>-h<><68><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD>L<EFBFBD><4C>H<EFBFBD><48><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>k<EFBFBD><6B><EFBFBD><EFBFBD>S<EFBFBD>[Hc<48>H<EFBFBD>G<EFBFBD><47><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD>:<3A><><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD>-<2D><><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD> <20><><EFBFBD><EFBFBD>
|
||
L<><4C>
|
||
H<><48>H<EFBFBD>5<EFBFBD>
|
||
fHn<48>H<EFBFBD>BfHn<48>H<EFBFBD><48> H<><48><EFBFBD>fl<66>I<EFBFBD>H)<29>L<EFBFBD>t$L<><4C>I<EFBFBD><49><EFBFBD>H<EFBFBD><48>L<EFBFBD><4C><EFBFBD>I<EFBFBD>~<7E>o<EFBFBD><6F><EFBFBD>Lc<4C>K<EFBFBD><4B><EFBFBD>L<EFBFBD><4C><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>I<EFBFBD><49>H<EFBFBD><48><EFBFBD><EFBFBD>H<EFBFBD><48>H<EFBFBD><48><EFBFBD><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD>5<EFBFBD><35>S<EFBFBD><53><EFBFBD>H<EFBFBD>
|
||
H<EFBFBD>/
|
||
L<><4C>H<EFBFBD>5
|
||
<20>v<EFBFBD><76><EFBFBD>H<EFBFBD>
|
||
H<>5
|
||
L<><4C><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD>5!
|
||
L<><4C><EFBFBD>!<21><><EFBFBD>H<EFBFBD>5
|
||
|
||
L<EFBFBD><EFBFBD><EFBFBD>'<27><><EFBFBD>H<EFBFBD><48><EFBFBD><EFBFBD><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD>H<EFBFBD><48><EFBFBD>L<EFBFBD><4C><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD>S<EFBFBD><53><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD>F<EFBFBD><46><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD>5<EFBFBD><35><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>1<EFBFBD>L<EFBFBD><4C><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>L<EFBFBD><4C><EFBFBD>5<EFBFBD><35><EFBFBD><EFBFBD>8<EFBFBD><38><EFBFBD><EFBFBD><EFBFBD>I<EFBFBD><49><EFBFBD>&<26><><EFBFBD>H<EFBFBD>=<3D>*M<><4D>H<EFBFBD><48><EFBFBD>@<40><><EFBFBD>u
|
||
H<><48><EFBFBD>1<EFBFBD><31><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>n<EFBFBD><6E><EFBFBD>A<EFBFBD>H<EFBFBD>E<EFBFBD>dH+%(u?H<>e<EFBFBD>D<EFBFBD><44>[A\A]A^]<5D>I<EFBFBD>M<EFBFBD>H<EFBFBD>=\*H<><48>
|
||
CH<EFBFBD>=L<><4C><EFBFBD><EFBFBD><EFBFBD>)<29>DH<44>=<3D>)H<><48>)H9<48>tH<74><48>)H<><48>t<EFBFBD>f.<2E>1<EFBFBD><31><EFBFBD><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD>=<3D>)H<>5<EFBFBD>)H)<29>H<EFBFBD><48>H<EFBFBD><48>?H<><48>H<EFBFBD>H<EFBFBD><48>tH<74>U)H<><48><EFBFBD><EFBFBD>fD<66><44><EFBFBD>=q)u/UH<55>=6)H<><48>t
|
||
H<>=:)<29><><EFBFBD><EFBFBD><EFBFBD>h<EFBFBD><68><EFBFBD><EFBFBD>I)]<5D><><EFBFBD><EFBFBD><EFBFBD>{<7B><><EFBFBD>f.<2E><>1<EFBFBD><31><EFBFBD>$<24><><EFBFBD>@H<>?<3F><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>)<29><>AUI<55><49>ATI<54><49>UH<55><48>SH<53><48>H<EFBFBD><48><EFBFBD>L<EFBFBD>D$@L<>L$H<><48>t7)D$P)L$`)T$p)<29>$<24>)<29>$<24>)<29>$<24>)<29>$<24>)<29>$<24>dH<64>%(H<>D$1<>H<EFBFBD>={(H<>T$ H<><48>$<24>$ <20>D$0H<30>DH<44>T$<24><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
|
||
<20><>v1H<31>=B(<28><><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD>D$dH+%(uH<75><48><EFBFBD>[]A\A]<5D><><EFBFBD><EFBFBD>H<EFBFBD>=(I<><49>1<EFBFBD><31>
|
||
H<EFBFBD><EFBFBD>H<EFBFBD>=7 H<>5H<35>=?'<27><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>e<EFBFBD><65><EFBFBD><EFBFBD>#<23><><EFBFBD><EFBFBD><EFBFBD><EFBFBD>f<EFBFBD>ATI<54><49><EFBFBD>f<EFBFBD><66><EFBFBD>H<EFBFBD>=<3D>'L<><4C>H<EFBFBD>I<EFBFBD><49><EFBFBD>1<EFBFBD><31><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD>i<EFBFBD><69><EFBFBD>1<EFBFBD>1<EFBFBD><31>.(<28>f<EFBFBD><66>=(UH<55><48>u#H<>5H<35><48><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD><48>t5H<35><48>]<5D><>DI<44><49>1<EFBFBD>H<EFBFBD>
|
||
<EFBFBD>H<EFBFBD>H<EFBFBD>5<EFBFBD>H<EFBFBD>=7&<26><>&<26><><EFBFBD><EFBFBD>X1<58>Z]A\A]<5D>H<EFBFBD><48><EFBFBD><EFBFBD><EFBFBD>ff.<2E><><EFBFBD>='UH<55><48>u#H<>5<EFBFBD>H<EFBFBD><48><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>H<EFBFBD><48>t5H<35><48>]<5D><>DI<44><49>1<EFBFBD>H<EFBFBD><48>RH<52>
|
||
!"<22><><EFBFBD><EFBFBD>H<EFBFBD>H<EFBFBD><48>DESKTOP_STARTUP_ID--no-ignore-config--media-library--dbusvlcorg.VideoLAN.VLCVLC/3.0.16VLC media playerglobalhotkeys,noneVLC is not supposed to be run as root. Sorry.
|
||
If you need to use real-time priorities and/or privileged TCP ports
|
||
you can use %s-wrapper (make sure it is Set-UID root and
|
||
```
|
||
|
||
And now of `which`.
|
||
|
||
```
|
||
waldek@hellodebian:~$ head /usr/bin/which
|
||
#! /bin/sh
|
||
set -ef
|
||
|
||
if test -n "$KSH_VERSION"; then
|
||
puts() {
|
||
print -r -- "$*"
|
||
}
|
||
else
|
||
puts() {
|
||
printf '%s\n' "$*"
|
||
waldek@hellodebian:~$
|
||
```
|
||
|
||
Notice how the `vlc` file is mostly **not human readable** but we can still make out some keywords?
|
||
The `which` file however is perfectly readable!
|
||
The first line of the `which` file is `#! /bin/sh` which is the path to the interpreter.
|
||
The `#!` is called a [shebang](https://en.wikipedia.org/wiki/Shebang_(Unix)).
|
||
We can dig into this to learn more about this mysterious `sh`.
|
||
|
||
```
|
||
waldek@hellodebian:~$ file /bin/sh
|
||
/bin/sh: symbolic link to dash
|
||
waldek@hellodebian:~$ which dash
|
||
/usr/bin/dash
|
||
waldek@hellodebian:~$ file /usr/bin/dash
|
||
/usr/bin/dash: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=cb6911fd56559717336c938bef1ce479b0a85b35, for GNU/Linux 3.2.0, stripped
|
||
waldek@hellodebian:~$
|
||
```
|
||
|
||
Surprise surprise!
|
||
The *interpreter* is a compiled program!
|
||
When you think about it it does make sense because at the end of the day the computer *only* understands machine instructions.
|
||
So when you execute a script each line of code is converted to machine instructions on the spot.
|
||
This makes scripts easier to write but slower at execution.
|
||
|
||
## More about paths
|
||
|
||
The prompt in our terminal tells us who we are, on which machine, and **where** we are located.
|
||
This where is symbolized with the `~` character.
|
||
But where is this where?
|
||
|
||
```
|
||
waldek@hellodebian:~$ pwd
|
||
/home/waldek
|
||
waldek@hellodebian:~$
|
||
```
|
||
|
||
The `pwd` program **p**rints our **w**orking **d**irectory, meaning where we are located on our system.
|
||
A user's home directory is symbolized with this tilde character.
|
||
We can move around our system with the `cd` command which is an abbreviation of **c**hange **d**irectory.
|
||
`cd` by itself seems to to *nothing* but this is not the case.
|
||
It's a *shortcut* to go to your user's home directory.
|
||
Let's try this out.
|
||
|
||
```
|
||
waldek@hellodebian:~$ cd
|
||
waldek@hellodebian:~$ cd /usr/bin
|
||
waldek@hellodebian:/usr/bin$ cd
|
||
waldek@hellodebian:~$ cd -
|
||
/usr/bin
|
||
waldek@hellodebian:/usr/bin$ cd
|
||
waldek@hellodebian:~$
|
||
```
|
||
|
||
The first line appears to do nothing because we are already in our home directory.
|
||
Next we move to the directory which contains the programs we discovered before and we see our prompt change.
|
||
It now shows *where* we are located!
|
||
The next line takes us back to our home and from there we can move *back to where we were before* with the `cd -` command.
|
||
This last command is also a handy *shortcut*!
|
||
|
||
Moving around is nice but once we arrive at our destination it would be practical to be able to list the files in that directory no?
|
||
This can be done with the `ls` program.
|
||
For example.
|
||
|
||
```
|
||
waldek@hellodebian:~$ cd /usr/bin/
|
||
waldek@hellodebian:/usr/bin$ ls
|
||
'[' getconf nmtui-hostname systemd-escape
|
||
7z getent nohup systemd-hwdb
|
||
7za getfacl notify-send systemd-id128
|
||
7zr getkeycodes nproc systemd-inhibit
|
||
aa-enabled getopt nroff systemd-machine-id-setup
|
||
aa-exec gettext nsenter systemd-mount
|
||
aconnect gettext.sh nslookup systemd-notify
|
||
add-apt-repository gio nstat systemd-path
|
||
addpart gio-querymodules nsupdate systemd-resolve
|
||
addr2line gjs ntfs-3g systemd-run
|
||
alsabat gjs-console ntfs-3g.probe systemd-socket-activate
|
||
alsaloop gkbd-keyboard-display ntfscat systemd-stdio-bridge
|
||
alsamixer glib-compile-schemas ntfscluster systemd-sysusers
|
||
alsatplg gmake ntfscmp systemd-tmpfiles
|
||
alsaucm gnome-calculator ntfsdecrypt systemd-tty-ask-password-agent
|
||
amidi gnome-calendar ntfsfallocate systemd-umount
|
||
amixer gnome-characters ntfsfix tabs
|
||
apg gnome-clocks ntfsinfo tac
|
||
apgbfm gnome-contacts ntfsls tail
|
||
aplay gnome-control-center ntfsmove tar
|
||
aplaymidi gnome-disk-image-mounter ntfsrecover tasksel
|
||
appres gnome-disks ntfssecaudit taskset
|
||
appstreamcli gnome-documents ntfstruncate tbl
|
||
apropos gnome-extensions ntfsusermap tbl-dctrl
|
||
apt gnome-extensions-app ntfswipe tee
|
||
apt-add-repository gnome-font-viewer numfmt telnet
|
||
apt-cache gnome-help numlockx telnet.netkit
|
||
apt-cdrom gnome-keyring nvlc tempfile
|
||
apt-config gnome-keyring-3 obamenu test
|
||
apt-extracttemplates gnome-keyring-daemon obconf thunar
|
||
apt-ftparchive gnome-logs obexctl Thunar
|
||
apt-get gnome-maps objcopy thunar-settings
|
||
apt-key gnome-music objdump thunar-volman
|
||
apt-listchanges gnome-screenshot obsession-exit thunar-volman-settings
|
||
apt-mark gnome-session obsession-logout tic
|
||
apt-sortpkgs gnome-session-classic obxprop time-admin
|
||
ar gnome-session-custom-session oclock timedatectl
|
||
arch gnome-session-inhibit od timeout
|
||
arecord gnome-session-quit odp2pdf tjbench
|
||
arecordmidi gnome-shell odp2ppt tkjpeg
|
||
as gnome-shell-extension-prefs ods2pdf tload
|
||
aseqdump gnome-shell-extension-tool odt2bib toc2cddb
|
||
aseqnet gnome-shell-perf-tool odt2doc toc2cue
|
||
aspell gnome-software odt2docbook toe
|
||
aspell-import gnome-sound-recorder odt2html top
|
||
atobm gnome-system-monitor odt2lt totem
|
||
atril gnome-terminal odt2pdf totem-video-thumbnailer
|
||
atril-previewer gnome-terminal.wrapper odt2rtf touch
|
||
atril-thumbnailer gnome-text-editor odt2sdw tput
|
||
awk gnome-thumbnail-font odt2sxw tr
|
||
axfer gnome-todo odt2txt traceproto
|
||
b2sum gnome-tweaks odt2txt.unoconv traceproto.db
|
||
baobab gnome-weather odt2xhtml traceroute
|
||
base32 gnome-www-browser odt2xml traceroute6
|
||
base64 gold ooxml2doc traceroute6.db
|
||
basename gpasswd ooxml2odt traceroute.db
|
||
basenc gpg ooxml2pdf traceroute-nanog
|
||
bash gpg-agent open tracker
|
||
bashbug gpgcompose openbox transmission-gtk
|
||
bccmd gpgconf openbox-lxde transset
|
||
bdftopcf gpg-connect-agent openbox-session troff
|
||
bdftruncate gpgparsemail openssl true
|
||
bf_compact gpgsm openvt truncate
|
||
bf_compact-bdb gpgsplit operon trust
|
||
bf_copy gpgtar orca tryaffix
|
||
bf_copy-bdb gpgv orca-dm-wrapper tset
|
||
bf_tar gpg-wks-server os-prober tsort
|
||
bf_tar-bdb gpg-zip p11-kit tty
|
||
bitmap gpic p7zip tzselect
|
||
bluemoon gpicview pacat ucf
|
||
bluetoothctl gprof pacmd ucfq
|
||
bluetooth-sendto grep pactl ucfr
|
||
bmtoa grep-aptavail padsp ucs2any
|
||
bogofilter grep-available pager udevadm
|
||
bogofilter-bdb grep-dctrl pa-info udisksctl
|
||
bogolexer grep-debtags pamon ul
|
||
bogolexer-bdb grep-status paperconf umax_pp
|
||
bogotune gresource paplay umount
|
||
bogotune-bdb groff parcellite uname
|
||
bogoupgrade grog parec unattended-upgrade
|
||
bogoupgrade-bdb grops parecord unattended-upgrades
|
||
bogoutil grotty parole uncompress
|
||
bogoutil-bdb groups partx unexpand
|
||
boltctl grub-editenv passwd unicode_start
|
||
bootctl grub-file paste unicode_stop
|
||
broadwayd grub-fstest pasuspender uniq
|
||
btattach grub-glue-efi patch unity-scope-loader
|
||
btmgmt grub-kbdcomp pathchk unlink
|
||
btmon grub-menulst2cfg pavucontrol unlzma
|
||
buildhash grub-mkfont pax11publish unmkinitramfs
|
||
bunzip2 grub-mkimage pcmanfm unoconv
|
||
busctl grub-mklayout pdb3 unopkg
|
||
busybox grub-mknetdir pdb3.9 unshare
|
||
bwrap grub-mkpasswd-pbkdf2 peekfd unxz
|
||
bzcat grub-mkrelpath perf unzip
|
||
bzcmp grub-mkrescue perl unzipsfx
|
||
bzdiff grub-mkstandalone perl5.32.1 update-alternatives
|
||
bzegrep grub-mount perl5.32-x86_64-linux-gnu update-desktop-database
|
||
bzexe grub-ntldr-img perlbug update-menus
|
||
bzfgrep grub-render-label perldoc update-mime-database
|
||
bzgrep grub-script-check perli11ndoc upower
|
||
bzip2 grub-syslinux2cfg perlivp uptime
|
||
bzip2recover gsettings perlthanks usb-devices
|
||
bzless gsf pgrep usbhid-dump
|
||
bzmore gsf-office-thumbnailer pic usbreset
|
||
c++ gsf-vba-dump pico userinfo
|
||
c89 gstreamer-codec-install piconv usermount
|
||
c89-gcc gtbl pidof userpasswd
|
||
c99 gtf pidwait users
|
||
c99-gcc gtk-builder-tool pinentry users-admin
|
||
cancel gtk-encode-symbolic-svg pinentry-gnome3 utmpdump
|
||
captoinfo gtk-launch pinentry-x11 VBoxClient
|
||
caribou-preferences gtk-query-settings ping VBoxClient-all
|
||
cat gtk-update-icon-cache ping4 VBoxControl
|
||
catchsegv gucharmap ping6 VBoxDRMClient
|
||
catman gunzip pinky vdir
|
||
cc gzexe pipewire vi
|
||
cd-create-profile gzip pipewire-media-session view
|
||
cd-fix-profile h2ph pipewire-pulse viewres
|
||
cd-iccdump h2xs pkaction vim.tiny
|
||
cd-it8 hciattach pkcheck vlc
|
||
cdrdao hciconfig pkcon vlc-wrapper
|
||
c++filt hcitool pkexec vmstat
|
||
chacl hd pkg-config vmwarectrl
|
||
chage head pkill w
|
||
chardet HEAD pkmon w3m
|
||
chardetect helpztags pkttyagent w3mman
|
||
charmap hex2hcd pl2pm wall
|
||
chattr hexdump pldd watch
|
||
chcon host plog watchgnupg
|
||
cheese hostid plymouth wc
|
||
chfn hostname pmap wdctl
|
||
chgrp hostnamectl pod2html wget
|
||
chmod htop pod2man whatis
|
||
choom i386 pod2text whereis
|
||
chown ibus pod2usage which
|
||
chrome-gnome-shell ibus-daemon podchecker whiptail
|
||
chrt ibus-setup poff who
|
||
chsh iceauth pon whoami
|
||
chvt ico POST widget
|
||
ciptool icombine ppt2odp word-list-compress
|
||
cjpeg iconv pr wpa_passphrase
|
||
ckbcomp id precat write
|
||
cksum iecset preconv write.ul
|
||
clear ijoin preunzip wrjpgcom
|
||
clear_console im-config prezip www-browser
|
||
cmp im-launch prezip-bin X
|
||
codepage infocmp print X11
|
||
col infotocap printenv x11perf
|
||
colcrt install printf x11perfcomp
|
||
colormgr install-menu prlimit x86_64
|
||
colrm install-printerdriver prove x86_64-linux-gnu-addr2line
|
||
column instmodsh proxy x86_64-linux-gnu-ar
|
||
comm intel-virtual-output prtstat x86_64-linux-gnu-as
|
||
compose ionice ps x86_64-linux-gnu-c++filt
|
||
consolehelper ip psfaddtable x86_64-linux-gnu-cpp
|
||
consolehelper-gtk ipcmk psfgettable x86_64-linux-gnu-cpp-10
|
||
corelist ipcrm psfstriptable x86_64-linux-gnu-dwp
|
||
cp ipcs psfxtable x86_64-linux-gnu-elfedit
|
||
cpan ipod-read-sysinfo-extended pslog x86_64-linux-gnu-g++
|
||
cpan5.32-x86_64-linux-gnu ipod-time-sync pstree x86_64-linux-gnu-g++-10
|
||
cpio iptables-xml pstree.x11 x86_64-linux-gnu-gcc
|
||
cpp ischroot ptar x86_64-linux-gnu-gcc-10
|
||
cpp-10 isdv4-serial-debugger ptardiff x86_64-linux-gnu-gcc-ar
|
||
c_rehash isdv4-serial-inputattach ptargrep x86_64-linux-gnu-gcc-ar-10
|
||
crontab ispell ptked x86_64-linux-gnu-gcc-nm
|
||
csplit ispell-wrapper ptksh x86_64-linux-gnu-gcc-nm-10
|
||
ctstat join ptx x86_64-linux-gnu-gcc-ranlib
|
||
cupstestppd join-dctrl pulseaudio x86_64-linux-gnu-gcc-ranlib-10
|
||
cut journalctl pw-cat x86_64-linux-gnu-gcov
|
||
cvlc jpegexiforient pw-cli x86_64-linux-gnu-gcov-10
|
||
cvt jpegtran pwd x86_64-linux-gnu-gcov-dump
|
||
cvtsudoers json_pp pw-dot x86_64-linux-gnu-gcov-dump-10
|
||
dash kbdinfo pw-dump x86_64-linux-gnu-gcov-tool
|
||
date kbd_mode pwdx x86_64-linux-gnu-gcov-tool-10
|
||
dbus-cleanup-sockets kbxutil pw-metadata x86_64-linux-gnu-gold
|
||
dbus-daemon kernel-install pw-mididump x86_64-linux-gnu-gprof
|
||
dbus-launch kill pw-midiplay x86_64-linux-gnu-ld
|
||
dbus-monitor killall pw-midirecord x86_64-linux-gnu-ld.bfd
|
||
dbus-run-session kmod pw-mon x86_64-linux-gnu-ld.gold
|
||
dbus-send l2ping pw-play x86_64-linux-gnu-lto-dump-10
|
||
dbus-update-activation-environment l2test pw-profiler x86_64-linux-gnu-nm
|
||
dbus-uuidgen laptop-detect pw-record x86_64-linux-gnu-objcopy
|
||
dbxtool last pw-reserve x86_64-linux-gnu-objdump
|
||
dconf lastb pw-top x86_64-linux-gnu-pkg-config
|
||
dd lastlog py3clean x86_64-linux-gnu-ranlib
|
||
deallocvt lcf py3compile x86_64-linux-gnu-readelf
|
||
debconf ld py3versions x86_64-linux-gnu-size
|
||
debconf-apt-progress ld.bfd pydoc3 x86_64-linux-gnu-strings
|
||
debconf-communicate ldd pydoc3.9 x86_64-linux-gnu-strip
|
||
debconf-copydb ld.gold pygettext3 x86_64-pc-linux-gnu-pkg-config
|
||
debconf-escape less pygettext3.9 xarchiver
|
||
debconf-set-selections lessecho python3 xargs
|
||
debconf-show lessfile python3.9 xauth
|
||
debianbts lesskey querybts xbiff
|
||
deb-systemd-helper lesspipe quodlibet xbrlapi
|
||
deb-systemd-invoke lexgrog qvlc xcalc
|
||
defmt-c lft ranger xclipboard
|
||
defmt-sh lft.db ranlib xclock
|
||
delpart libnetcfg rbash xcmsdb
|
||
delv libreoffice rcp xconsole
|
||
desktop-file-edit libwacom-list-local-devices rctest xcursorgen
|
||
desktop-file-install light-locker rdjpgcom xcutsel
|
||
desktop-file-validate light-locker-command rdma xdg-autostart
|
||
df link readelf xdg-dbus-proxy
|
||
dfu-tool linux32 readlink xdg-desktop-icon
|
||
dh_bash-completion linux64 realpath xdg-desktop-menu
|
||
dh_dkms linux-boot-prober rendercheck xdg-email
|
||
dh_installxmlcatalogs linux-check-removal renice xdg-icon-resource
|
||
dh_perl_openssl linux-update-symlinks reportbug xdg-mime
|
||
diff linux-version report-hw xdg-open
|
||
diff3 listres reset xdg-screensaver
|
||
dig ln resizecons xdg-settings
|
||
dir lnstat resizepart xdg-user-dir
|
||
dircolors loadkeys resolvectl xdg-user-dirs-gtk-update
|
||
dirmngr loadunimap rev xdg-user-dirs-update
|
||
dirmngr-client localc rfcomm xditview
|
||
dirname locale rgrep xdpyinfo
|
||
discover-config localectl rhythmbox xdriinfo
|
||
djpeg localedef rhythmbox-client xedit
|
||
dmesg lodraw rifle Xephyr
|
||
dm-tool loffice ristretto xev
|
||
dnsdomainname lofromtemplate rlogin xeyes
|
||
dnstap-read logger rm xfburn
|
||
doc2odt login rmdir xfce4-about
|
||
doc2pdf loginctl rnano xfce4-accessibility-settings
|
||
domainname logname routef xfce4-appearance-settings
|
||
dotlockfile loimpress routel xfce4-appfinder
|
||
dpkg lomath rpcgen xfce4-clipman
|
||
dpkg-architecture look rsh xfce4-clipman-history
|
||
dpkg-buildflags loweb rstart xfce4-clipman-settings
|
||
dpkg-buildpackage lowntfs-3g rstartd xfce4-color-settings
|
||
dpkg-checkbuilddeps lowriter rtstat xfce4-dict
|
||
dpkg-deb lp runcon xfce4-display-settings
|
||
dpkg-distaddfile lpoptions run-mailcap xfce4-find-cursor
|
||
dpkg-divert lp_solve run-parts xfce4-keyboard-settings
|
||
dpkg-genbuildinfo lpstat run-with-aspell xfce4-mime-helper
|
||
dpkg-genchanges ls rview xfce4-mime-settings
|
||
dpkg-gencontrol lsattr rvlc xfce4-mouse-settings
|
||
dpkg-gensymbols lsblk rygel xfce4-notifyd-config
|
||
dpkg-maintscript-helper lsb_release sane-find-scanner xfce4-panel
|
||
dpkg-mergechangelogs lscpu savelog xfce4-popup-applicationsmenu
|
||
dpkg-name lsinitramfs scanimage xfce4-popup-clipman
|
||
dpkg-parsechangelog lsipc scp xfce4-popup-clipman-actions
|
||
dpkg-query lslocks scp-dbus-service xfce4-popup-directorymenu
|
||
dpkg-realpath lslogins screendump xfce4-popup-places
|
||
dpkg-scanpackages lsmem script xfce4-popup-whiskermenu
|
||
dpkg-scansources lsmod scriptlive xfce4-popup-windowmenu
|
||
dpkg-shlibdeps lsns scriptreplay xfce4-power-manager
|
||
dpkg-source lsof scrot xfce4-power-manager-settings
|
||
dpkg-split lspci sdiff xfce4-screenshooter
|
||
dpkg-statoverride lspgpot sdptool xfce4-sensors
|
||
dpkg-trigger lsusb sdw2odt xfce4-session
|
||
dpkg-vendor lto-dump-10 seahorse xfce4-session-logout
|
||
du luit sed xfce4-session-settings
|
||
dumpkeys lwp-download see xfce4-settings-editor
|
||
dwp lwp-dump select-default-iwrap xfce4-settings-manager
|
||
echo lwp-mirror select-editor xfce4-taskmanager
|
||
edit lwp-request sensible-browser xfce4-terminal
|
||
editor lxappearance sensible-editor xfce4-terminal.wrapper
|
||
editres lxclipboard sensible-pager xfconf-query
|
||
egrep lxde-logout sensors xfd
|
||
eject lxhotkey sensors-conf-convert xfdesktop
|
||
elfedit lxinput seq xfdesktop-settings
|
||
enc2xs lxlauncher sessreg xfhelp4
|
||
encguess lxlock setarch xflock4
|
||
enchant-2 lxmusic setfacl xfontsel
|
||
enchant-lsmod-2 lxpanel setfont xfrun4
|
||
env lxpanelctl setkeycodes xfsettingsd
|
||
envsubst lxpolkit setleds xfwm4
|
||
eog lxrandr setlogcons xfwm4-settings
|
||
eqn lxsession setmetamode xfwm4-tweaks-settings
|
||
evince lxsession-db setpci xfwm4-workspace-settings
|
||
evince-previewer lxsession-default setpriv xgamma
|
||
evince-thumbnailer lxsession-default-apps setsid xgc
|
||
evolution lxsession-default-terminal setterm xhost
|
||
ex lxsession-edit setupcon xiccd
|
||
exfalso lxsession-logout setvtrgb xinit
|
||
exifautotran lxsession-xdg-autostart setxkbmap xkbbell
|
||
exo-desktop-item-edit lxsettings-daemon sftp xkbcomp
|
||
exo-open lxtask sg xkbevd
|
||
expand lxterminal sh xkbprint
|
||
expiry lynx sha1sum xkbset
|
||
expr lzcat sha224sum xkbset-gui
|
||
factor lzcmp sha256sum xkbvleds
|
||
faillog lzdiff sha384sum xkbwatch
|
||
faked-sysv lzegrep sha512sum xkeystone
|
||
faked-tcp lzfgrep shares-admin xkill
|
||
fakeroot lzgrep shasum xload
|
||
fakeroot-sysv lzless shotwell xlogo
|
||
fakeroot-tcp lzma showconsolefont xls2ods
|
||
fallocate lzmainfo showkey xlsatoms
|
||
false lzmore showrgb xlsclients
|
||
fc-cache make shred xlsfonts
|
||
fc-cat make-first-existing-target shuf xmag
|
||
fc-conflist mako-render simple-scan xman
|
||
fc-list malcontent-client size xmessage
|
||
fc-match malcontent-control skill xmms2d
|
||
fc-pattern man slabtop xmms2-launcher
|
||
fc-query mandb sleep xmodmap
|
||
fc-scan manpath slogin xmore
|
||
fc-validate man-recode smproxy Xorg
|
||
fgconsole mapscrn snice xprop
|
||
fgrep mawk soelim xrandr
|
||
file mcookie soffice xrdb
|
||
file-roller md5sum software-properties-gtk xrefresh
|
||
fincore md5sum.textutils sort xsane
|
||
find mdig sort-dctrl xscreensaver
|
||
findaffix memusage sotruss xscreensaver-command
|
||
findmnt memusagestat spa-acp-tool xscreensaver-demo
|
||
firefox mesa-overlay-control.py spa-inspect xscreensaver-getimage
|
||
firefox-esr mesg spa-monitor xscreensaver-getimage-file
|
||
flock mid3cp spa-resample xscreensaver-getimage-video
|
||
fmt mid3iconv spd-conf xscreensaver-systemd
|
||
fold mid3v2 spd-say xscreensaver-text
|
||
fonttosfnt migrate-pubring-from-classic-gpg spdsend x-session-manager
|
||
free mimeopen speaker-test xset
|
||
funzip mimetype speech-dispatcher xsetmode
|
||
fuser mkdir splain xsetpointer
|
||
fusermount mkfifo split xsetroot
|
||
fusermount3 mkfontdir splitfont xsetwacom
|
||
fwupdagent mkfontscale sprof xsm
|
||
fwupdate mk_modmap ss xstdcmap
|
||
fwupdmgr mknod ssh xsubpp
|
||
fwupdtool mktemp ssh-add x-terminal-emulator
|
||
fwupdtpmevlog mmcli ssh-agent xvidtune
|
||
g++ moggsplit ssh-argv0 xvinfo
|
||
g++-10 monitor-sensor ssh-copy-id Xwayland
|
||
gamma4scanimage more ssh-keygen xwd
|
||
gapplication mount ssh-keyscan x-window-manager
|
||
gatttool mountpoint startlxde xwininfo
|
||
gcalccmd mousepad start-pulseaudio-x11 xwud
|
||
gcc mpris-proxy startx x-www-browser
|
||
gcc-10 mt startxfce4 xxd
|
||
gcc-ar mt-gnu stat xz
|
||
gcc-ar-10 mtrace stdbuf xzcat
|
||
gcc-nm munchlist streamzip xzcmp
|
||
gcc-nm-10 mutagen-inspect strings xzdiff
|
||
gcc-ranlib mutagen-pony strip xzegrep
|
||
gcc-ranlib-10 mv stty xzfgrep
|
||
gcm-import namei su xzgrep
|
||
gcm-inspect nano sudo xzless
|
||
gcm-picker nautilus sudoedit xzmore
|
||
gcm-viewer nautilus-autorun-software sudoreplay yelp
|
||
gcov nawk sum yes
|
||
gcov-10 nc sushi ypdomainname
|
||
gcov-dump nc.traditional su-to-root zcat
|
||
gcov-dump-10 neqn svlc zcmp
|
||
gcov-tool netcat switcherooctl zdiff
|
||
gcov-tool-10 networkctl sxw2odt zdump
|
||
gcr-viewer newgrp synaptic-pkexec zegrep
|
||
gdbus ngettext sync zenity
|
||
gdialog nice system-config-printer zfgrep
|
||
gdk-pixbuf-csource nisdomainname system-config-printer-applet zforce
|
||
gdk-pixbuf-pixdata nl systemctl zgrep
|
||
gdk-pixbuf-thumbnailer nm systemd zipdetails
|
||
gdm-control nm-applet systemd-analyze zipgrep
|
||
gdmflexiserver nmcli systemd-ask-password zipinfo
|
||
gdm-screenshot nm-connection-editor systemd-cat zless
|
||
gedit nm-online systemd-cgls zmore
|
||
gencat nmtui systemd-cgtop znew
|
||
geqn nmtui-connect systemd-delta
|
||
GET nmtui-edit systemd-detect-virt
|
||
waldek@hellodebian:/usr/bin$
|
||
```
|
||
|
||
That's a **lot** of programs!
|
||
Can you find `cd` in there?
|
||
Spoiler alert, you wont...
|
||
Maybe it's located somewhere else?
|
||
Let's have a look.
|
||
|
||
```
|
||
waldek@hellodebian:/usr/bin$ which cd
|
||
waldek@hellodebian:/usr/bin$
|
||
```
|
||
|
||
`cd` is not a program but a builtin command.
|
||
From a practical point of view there is no difference but I do like to mention it for completeness.
|
||
Later down the line it will help you to contextualize the differences between shells a bit better.
|
||
But built into *what*?
|
||
Below you can see a snippet of a part of the `bash-builtin` manual.
|
||
For now just accept the specific shell we're using is called `bash`.
|
||
|
||
```
|
||
BASH-BUILTINS(7) Miscellaneous Information Manual BASH-BUILTINS(7)
|
||
|
||
NAME
|
||
bash-builtins - bash built-in commands, see bash(1)
|
||
|
||
SYNOPSIS
|
||
bash defines the following built-in commands: :, ., [, alias, bg, bind, break, builtin, case, cd, command, compgen, complete, continue, de‐
|
||
clare, dirs, disown, echo, enable, eval, exec, exit, export, fc, fg, getopts, hash, help, history, if, jobs, kill, let, local, logout, popd,
|
||
printf, pushd, pwd, read, readonly, return, set, shift, shopt, source, suspend, test, times, trap, type, typeset, ulimit, umask, unalias,
|
||
unset, until, wait, while.
|
||
```
|
||
|
||
### Absolute and relative paths
|
||
|
||
> All roads lead to Rome.
|
||
|
||
There are multiple ways to go to the same location on your system.
|
||
You can always go either in an **absolute** way, or in *multiple* **relative** ways.
|
||
The root of your system is `/` and to list what we can find there we can use `ls`.
|
||
|
||
```
|
||
waldek@hellodebian:~$ cd /
|
||
waldek@hellodebian:/$ ls
|
||
bin dev home initrd.img.old lib32 libx32 media opt root sbin sys usr vmlinuz
|
||
boot etc initrd.img lib lib64 lost+found mnt proc run srv tmp var vmlinuz.old
|
||
waldek@hellodebian:/$
|
||
```
|
||
|
||
From here we can go back home in multiple ways.
|
||
|
||
```
|
||
waldek@hellodebian:/$ cd
|
||
waldek@hellodebian:~$ cd -
|
||
/
|
||
waldek@hellodebian:/$ cd home/waldek/
|
||
waldek@hellodebian:~$ cd -
|
||
/
|
||
waldek@hellodebian:/$ cd /home/waldek/
|
||
waldek@hellodebian:~$
|
||
```
|
||
|
||
The first one is the handy shortcut we learned, and we go back to the root of our system with the `cd -` shortcut.
|
||
The following two manipulations look very similar but there is a subtle difference.
|
||
The first one `home/waldek` is a **relative** path, and the second one `/home/waldek` is an **absolute** one.
|
||
Relative paths depend on where you are located, absolute ones always point to the same location.
|
||
An example.
|
||
|
||
```
|
||
waldek@hellodebian:~$ cd /usr/bin/
|
||
waldek@hellodebian:/usr/bin$ cd /home/waldek/
|
||
waldek@hellodebian:~$ cd -
|
||
/usr/bin
|
||
waldek@hellodebian:/usr/bin$ cd home/waldek
|
||
-bash: cd: home/waldek: No such file or directory
|
||
waldek@hellodebian:/usr/bin$
|
||
```
|
||
|
||
The second command fails because from where I'm standing, there is no folder called `home/waldek`!
|
||
I can however still go to my home in a relative way but I need to *go back* a few directories first.
|
||
|
||
```
|
||
waldek@hellodebian:/usr/bin$ cd ../../home/waldek/
|
||
waldek@hellodebian:~$ pwd
|
||
/home/waldek
|
||
waldek@hellodebian:~$
|
||
```
|
||
|
||
The `..` means go **back** one directory so in our example we go back **two** directories, which brings us to the `/` of our system and from there we go **up** to `home` and then `waldek`.
|
||
|
||
### Exercise
|
||
|
||
Explore your system a bit using `cd` and `ls`.
|
||
You'll probably encounter some weird messages along the way.
|
||
Keep note of them so we can discuss it together.
|
||
|
||
### `root` and `/` and `/root` are not the same thing
|
||
|
||
## A pit stop to review what we've learned so far
|
||
|
||
Below is a list of programs and command we've seen so far.
|
||
|
||
|command|desciption|
|
||
|---|---|
|
||
|systemctl|manipulate running services|
|
||
|apt|the Debian package manager|
|
||
|htop|a command line task manager we installed|
|
||
|vlc|a video player we installed|
|
||
|date|display the time of day|
|
||
|which|show the path to an executable|
|
||
|file|print more information about a file's content|
|
||
|head|show the first lines of a file|
|
||
|pwd|print working directory|
|
||
|cd|change directory|
|
||
|ls|list content of a directory|
|
||
|