merge

wiki/linux/7-zip.md

@@ -11,6 +11,8 @@ from the [AUR](/wiki/linux/package_manager.md#arch-linux-pacman-and-yay).
 
 ## Usage
 
+The following section describes various ways of usage of 7-zip.
+
 ### Compressing and Uncompressing a Directory
 
 For directories to be compressed the Lempel–Ziv–Markov chain algorithm is recommended.

wiki/linux/arch-linux.md

@@ -61,3 +61,61 @@ initrd  /<installed microcode package>.img
 ```
 
 `<installed microcode package>` is either `amd-ucode` or `intel-ucode`.
+
+## Troubleshooting
+
+This section addresses problems that can occur when using Arch Linux.
+
+### Troubleshooting Setup for not Bootable Systems
+
+This section focusses on a basic guide to troubleshoot systems that are not bootable.
+To access the files of the system an Arch Linux boot stick has to be created as explained in
+[a previous section](#iso-medium).
+After booting into it set your keymap layout using the `loadkeys` setup similar to
+[the installation preparation](/wiki/linux/arch-linux/installation.md#1-preparation).
+Afterwards [mount](/wiki/linux/disk-management.md#mounting) the partition that contains the root
+file system to the `/mnt` directory.
+It is possible that LUKS encrypted file systems need to be
+[opened](/wiki/linux/dm-crypt.md#openclose-an-encrypted-volume) and then mounted using the
+`/dev/mapper` symbolic link.
+On some systems there are home or boot file system that have to be mounted on `/mnt/boot` or
+`/mnt/home` after mounting the root file system.
+Afterwards use `arch-chroot /mnt` to get into the not bootable system.
+Now the command line of the system can be accessed for troubleshooting.
+After troubleshooting `exit` the system and [unmount](/wiki/linux/disk-management.md#mounting) all previously
+mounted file systems and try to boot back into the system.
+
+If the system broke during an update then the easiest way to fix it, is by running the same update
+command again.
+The used command can be found in `/var/log/pacman.log`.
+Make sure to run exactly this command.
+Afterwards try to reboot into the system.
+
+Another common source for not bootable systems is
+[the initial ramdisk](#problems-with-the-initial-ramdisk).
+
+### Problems with the Initial Ramdisk
+
+A common problem (especially after a interrupted update lies in the initial ramdisk environment).
+An error like this will mean that the system is
+[not bootable](#troubleshooting-setup-for-not-bootable-systems).
+To fix this generate the initial ramdisk manually as described in
+[the mkinitcpio entry](/wiki/linux/mkinitcpio.md#manually-generate-initial-ramdisk).
+
+### Stuck in Boot Screen
+
+There is a known problem described in the Arch Linux forums by
+[TheRealNubby](https://bbs.archlinux.org/viewtopic.php?id=300292) where the system goes into a
+perceived freeze after the boot process.
+This problem seems to be most prevalent on systems that use an [Nvidia](/wiki/nvidia.md) GPU
+since its only known occurences were found on Nvidia GTX 1080 GPUs.
+The boot screen will not show any errors and when
+[troubleshooting using a installation medium](#troubleshooting-setup-for-not-bootable-systems)
+logs like [the ones of SystemD](/wiki/linux/systemd.md#retrieving-the-systemd-logs) will look
+normal and won't show any errors.
+
+In this case there is the possibility that logging into Arch Linux blindly will work.
+For this type in user name and password some moments after the perceived freeze as you normally
+would do if the login screen came up.
+If the graphical interface still does not work, the command to start the graphical interface (like 
+`startx` for [X11](/wiki/linux/x_window_system.md) systems) can also work.

wiki/linux/audio.md

@@ -34,3 +34,11 @@ With additional software it can also be used to control audio/music by pressing
 hotkeys.
 This is explained in the
 [PlayerCTL entry](/wiki/linux/playerctl.md#using-hotkeys).
+
+## Sound Board
+
+There are various available software solutions for sound boards.
+One option is [CasterSoundboard](https://github.com/JupiterBroadcasting/CasterSoundboard).
+Another is the cue player
+[Linux Show Player](https://linux-show-player-users.readthedocs.io/en/latest/index.html) which
+should be installed using [flatpak](/wiki/linux/flatpak.md) (`org.linuxshowplayer.LinuxShowPlayer`).

wiki/linux/display_control.md

@@ -0,0 +1,14 @@
+# Display Control
+
+Display control describes the process of controlling the display with means other than the hardware
+buttons.
+
+## DDC
+
+DDC - short for Display Data Channel - is a specific way to control the display.
+On [Linux](/wiki/linux.md)-based Systems this can be achieved by using the
+[`ddcutil`](https://github.com/rockowitz/ddcutil) command line interface that can be found in the
+package of the same name.
+For a graphical user interface [`ddcui`](https://github.com/rockowitz/ddcui) can be used.
+After installation it is possible that the system needs to be restarted due to the i2c-dev kernel
+module.

wiki/linux/flatpak.md

@@ -6,7 +6,7 @@ linux systems.
 ## Setup
 
 The `flatpak` package can be installed by most distribution specific package
-managers (e.g. [pacman or yay](./arch-linux/package_manager.md)).
+managers (e.g. [pacman or yay](/wiki/linux/package_manager.md#arch-linux-pacman-and-yay)).
 After installation it is important to add [flathub](https://flathub.org/home),
 a source for many Flatpak packages.
 The addition of this can be done by running

wiki/linux/font_configuration.md

@@ -45,7 +45,7 @@ A configuration typically looks like the following lines.
 
 This configuration requires some fonts that are not necessarily present in any
 Linux installation so they may have to be installed.
-Follow the section on [adding new fonts](#adding-new-font) and
+Follow the section on [adding new fonts](#adding-new-font-to-configuration) and
 [recommended fonts](#recommended-fonts) as needed.
 
 ## Usage
@@ -53,6 +53,33 @@ Follow the section on [adding new fonts](#adding-new-font) and
 This section addresses important commands and packages for the configuration of
 fonts.
 
+### Show Characters Of A Font
+
+Using [FontForge](https://fontforge.org/en-US/) all characters of a given `.ttf` file can be shown.
+The following shows the structure of a command to call FontForge with a file.
+
+```ssh
+fontforge arial.ttf
+```
+
+### Add TTF Font
+
+A font can be added to the local users fonts using a `.ttf` file.
+The file has to be copied into the local fonts directory `~/.local/share/fonts`.
+Afterwards the [cache should be reloaded](#reload-the-cache).
+Finally the font can be [found](#list-or-find-font-family).
+
+### Reload the Cache
+
+The cache needs to be reloaded in certain situations like after a new font
+has been added.
+This can be achieved by the following command.
+
+
+```sh
+fc-cache -f -c
+```
+
 ### List or Find Font Family
 
 A list of all fonts can be displayed using the command `fc-match -a`.
@@ -63,17 +90,18 @@ For matching the command `fc-match -s <search term>` is be used.
 This will display a list of font families that match best with the given search
 term.
 
-### Adding New Font
+### Adding New Font to Configuration
 
 A new font can be added by placing its name inside `<family>`/`</family>`-tags.
 Make sure to place it inside the correct [font family](/wiki/font.md#typefaces).
 If you want to add a font into the configuration make sure its name
 [matches](#list-or-find-font-family) correctly.
 
+
 ### Recommended Fonts
 
 In this section various fonts are listed for the different typefaces.
-Make sure to follow [the adding new fonts section](#adding-new-font) after
+Make sure to follow [the adding new fonts section](#adding-new-font-to-configuration) after
 installing new fonts.
 
 #### Monospace
@@ -119,3 +147,14 @@ displayed properly.
 [JoyPixels](https://joypixels.com) feature many emoji icons.
 The fonts can be obtained from their [website](https://joypixels.com/download)
 or for most distributions from the `ttf-joypixels` package.
+
+#### Special Fonts
+
+This section lists some fonts that are good in certain situations but are not
+intended to be used as day-to-day font.
+
+- [MagicMedieval & MagicSymbols](http://www.thealmightyguru.com/GameFonts/Series-MagicTheGathering.html)
+  are fonts that are similar to the font used in the game
+  [Magic: The Gathering](/wiki/games/magic%3A_the_gathering.md).
+  An overview of the glyphs can be found in a
+  [StackExchange post by Cicada](https://tex.stackexchange.com/questions/570890/how-can-i-typeset-magic-the-gathering-symbols-using-the-pifont-package-in-latex).

wiki/linux/git_(client).md

@@ -22,6 +22,8 @@ This section addresses various use cases of git.
 
 There is also an interactive
 [fixup guide by Seth Robertson](https://sethrobertson.github.io/GitFixUm/fixup.html).
+Robertson also made guides on [post production](https://github.com/SethRobertson/GitPostProduction)
+and [best practices](http://sethrobertson.github.io/GitBestPractices).
 
 ### Ignore files having local changes
 

wiki/linux/ip.md

@@ -28,10 +28,10 @@ Disabling works accordingly by running:
 ip link set wlan0 down
 ```
 
-### Get Outside IP
+### Get Outside IP Address
 
 For VPN and other applications using a tunnel it can be useful to check the
-outside IP of your system.
+outside [IP address](/wiki/ip_address.md) of your system.
 The following command uses the `dig` command.
 It is either bundled in the `dig` package - like in
 [Arch Linux](/wiki/linux/arch-linux.md) - or in the `dnsutils`

wiki/linux/netplan.md

@@ -8,7 +8,7 @@ linux system via YAML files.
 ### Add more IP addresses to a system
 
 In the file `/etc/netplan/50-cloud-init.yaml` create an `addresses:` section
-for a device (for example an ethernet device) and list the IP addresses you
+for a device (for example an ethernet device) and list the [IP addresses](/wiki/ip_address.md) you
 want to add to the system to it.
 It has to be noted, that the added addresses should be outside of the DHCP
 range of your router.

wiki/linux/openssl.md

@@ -25,3 +25,13 @@ where `plaintext.txt` is the message to encrypt and `encrypted.txt` is the
 encrypted message.
 You can decrypt the message using the private key `private.key` as follows
 `openssl rsautl -decrypt -inkey private.key -in encrypted.txt -out plaintext.txt`.
+
+### Password Generator
+
+OpenSSL can be used to create a password.
+For this use the following command.
+It will create a hexadecimal password with 32 characters.
+
+```ssh
+openssl rand -hex 32
+```

wiki/linux/package_manager.md

@@ -17,9 +17,31 @@ It features the same syntax.
 
 ### Usage
 
-This section addresses various uses of the pacman and yay package managers.
+This section addresses various usages of the arch linux package managers.
 
-#### Clean Cache
+#### Manual Installation of a `PKGBUILD` File
+
+A `PKGBUILD` file is a [shell](/wiki/linux/shell.md) script that contains the installation 
+information that is required by the Arch Linux.
+Using the `makepkg` command it can be installed like the following command shows.
+
+```sh
+makepkg -sirc
+```
+
+Afterwards it is installed on the system and can be further managed (especially uninstalled) by the
+Pacman package manager.
+
+#### Installing an AUR Program with a Specific Version
+
+The installation of a specific version of an AUR program can be easily achieved.
+For this navigate to the AUR page of the program to install.
+On the right-hand side click on `View Changes` and select the version you want to install in the
+commit list.
+Next to `download` a `.tar.gz` file can be downloaded which includes a `PKGBUILD` file.
+Afterwards it needs to be [uncompressed](/wiki/linux/tar.md#uncompressing-a-tar-archive).
+
+#### Clear Cache
 
 The cache of all packages except the one installed can be deleted by running the following command.
 
@@ -27,6 +49,10 @@ The cache of all packages except the one installed can be deleted by running the
 pacman -Sc
 ```
 
+### Troubleshooting
+
+This section addresses various uses of the pacman and yay package managers.
+
 #### Update Mirrorlist
 
 After a while not updating the system it is possible for the mirrorlist to be

wiki/linux/papis.md

@@ -0,0 +1,133 @@
+# Papis
+
+[Papis](/wiki/linux/papis.md) is a [command-line based](/wiki/linux/shell.md) for
+[Linux](/wiki/linux.md) [bibliography manager](/wiki/bibliographic_software.md) that can be used
+for LaTeX using the BibTeX format.
+
+## Setup
+
+Papis can be installed on most distributions by acquiring the `papis` package.
+Alternatively it can be downloaded from [the GitHub page](https://github.com/papis/papis).
+
+### Configuration
+
+To use Papis a config file needs to be created.
+The path of the global config file is `~/.config/papis/config`.
+A minimal config can look like the following.
+Make sure to change the path of the papers directory.
+
+```txt
+[papers]
+dir = ~/cloud/bibliography/papis
+
+[settings]
+default-library = papers
+```
+
+## Usage
+
+The following section describes various ways of usage of Papis.
+
+### Adding, Removing, Editing and Browsing Entries
+
+An entry can be added by running a command similar to the following.
+The values for the different keys needs to be changed, added or omitted accordingly.
+
+```sh
+papis add ~/Documents/interesting.pdf \
+    --folder-name interesting-paper-2021 \
+    --set author 'John Smith' \
+    --set title 'The interesting life of bees' \
+    --set year 1985 \
+    --set tags 'biology interesting bees'
+```
+
+Papis can also add sources directly via their DOI code.
+
+```sh
+papis add --from doi 10.10763/1.3237134
+```
+
+For the most well known journals are also recognized by Papis
+
+```sh
+papis add https://arxiv.org/abs/1712.03134
+```
+
+To remove an entry the following command can be run.
+Afterwards the entry that should be removed can be easily selected via the terminal user interface.
+
+```sh
+papis rm
+```
+
+Entries can be edited by using the following command.
+
+```sh
+papis edit
+```
+
+Entries can be browsed and viewed either in the terminal or via a local website.
+For the first run the following command.
+
+```sh
+papis browse
+```
+
+For the latter the following command can be run to start the server.
+The command-line output will show the address to reach the service.
+
+```sh
+papis serve
+```
+
+### Create a BibTeX file
+
+A BibTeX file containing all the entries of all the libraries can be created by running the
+following command.
+For this the command will create a file called `lib.bib`.
+
+```sh
+papis export --all --format bibtex --out lib.bib
+```
+
+### Clearing the Cache
+
+The cache of Papis can be cleared by running the following command.
+
+```sh
+papis --cc
+```
+
+### Import Entries from a BibTeX File
+
+This section will discuss the way to add the contents of a BibTeX file to the database.
+First the BibTeX file (in this case called `mylib.bib`) will be used to create a new database
+inside the folder `tmp-db`.
+
+```sh
+papis bibtex read mylib.bib import -a -o tmp-db
+```
+
+Afterwards the contents of the temporary database should be checked to be correctly imported.
+
+```sh
+papis -l tmp-db edit
+```
+
+Afterwards the contents of the temporary library should be moved to the actualy directory where
+papis stores its entries.
+The path for that can be found in the [config file](#configuration).
+
+```sh
+mv tmp-db/* /path/to/your/library/folder/
+```
+
+Finally the cache needs to be cleared for Papis to display the new entries correctly.
+
+```sh
+papis --cc
+```
+
+Finally the cache needs to be [cleared](#clearing-the-cache) for Papis to display the new entries
+correctly.

wiki/linux/pipewire.md

@@ -10,18 +10,212 @@ For clients that use the [PulseAudio](/wiki/linux/pulseaudio.md) API
 packages on other distros) can be installed.
 It will automatically remove unneeded and conflicting PulseAudio packages.
 Additionally `pipewire-alsa` and `pipewire-jack` for JACK and Alsa clients are
-available.
+available and recommended to install for full compatibility with most software.
 Make sure to restart to be sure everything is running correctly.
 
 ## Usage
 
+This section will focus on the usage of Pipewire.
+
+### Mixing
+
 For simple sound processing in the form of volume adjustment as well as setting
 the default input and output devices
 [`pavucontrol`](https://freedesktop.org/software/pulseaudio/pavucontrol/) can be
 used as a simple mixer.
+
+### Routing
+
+This section focusses on graph-based interfaces also called patchbays.
 For more advanced routing [qpwgraph](https://github.com/rncbc/qpwgraph) can be used, but the
-GTK-based [Helvum](https://gitlab.freedesktop.org/pipewire/helvum) is recommended.
-Both are graph-based interface also called patchbays.
+GTK-based [Helvum](https://gitlab.freedesktop.org/pipewire/helvum) is also available.
+The third available option is [Patchance](https://github.com/Houston4444/Patchance) - this is the
+currently recommended software of this wiki.
+
+### Equalizer, Noise Reduction, etc
+
 For further sound processing the easiest way to do so is using
 [easyeffects](/wiki/linux/easyeffects.md) which features a wide range of effects
 to apply to sound streams including noise reduction.
+
+### Get ID of an Input or Output
+
+Using the following command a list of all connected input and output aswell as streams and devices
+can be displayed.
+
+```sh
+wpctl status
+```
+
+Under the `Sinks` the outputs are displayed and under `Sources` the inputs.
+Defaults are noted with an asterix.
+The identificator is displayed prior to the name of the input, output, device or stream.
+
+If a device name is known (in this case `"Starship/Matisse HD Audio Controller Analog Stereo"`).
+The following command will return its identificator.
+
+```sh
+NAME=$(wpctl status | grep "Starship/Matisse HD Audio Controller Analog Stereo")
+ID=$( echo $NAME | cut -d '.' -f 1 | cut -c 11-)
+
+echo ID: $ID
+```
+
+### Loopback Input
+
+An input can be output to the default output by using the following command.
+In that command `<id>` is the identificator of the input that should be looped back.
+It needs to be set accordingly.
+
+```sh
+pw-loopback -C <id>
+```
+
+### Virtual Devices
+
+This section focusses on the temporary and permanent creation and removal of virtual devices like
+virtual sinks and sources aswell as coupled nodes like loopbacks.
+
+#### Creating a Null Device
+
+This section will focus on the creation of a dummy device.
+That is a virtual device that can be selected as output but is not used by default.
+This can be useful to record applications as their sound can cleanly be passed to the dummy device
+which will eliminate other applications sounds.
+If the goal is to record and listen to an application at the same time navigate to
+[the application loopback section](#creating-an-application-loopback)
+
+The source for this section of the entry is derived by
+[Pipewire Gitlab site](https://gitlab.freedesktop.org/pipewire/pipewire/-/wikis/Virtual-Devices#single-nodes).
+
+A dummy device, or null sink, can be created permanently by creating a `.conf` file inside the
+`~/.config/pipewire/pipewire.conf.d` directory with the following lines.
+
+
+```txt
+context.objects = [
+    {   factory = adapter
+        args = {
+            factory.name     = support.null-audio-sink
+            node.name        = "null-sink-0"
+            node.description = "Null Sink 0"
+            media.class      = Audio/Sink
+            audio.position   = [ FL FR ]
+            monitor.channel-volumes = true
+            monitor.passthrough = true
+            adapter.auto-port-config = {
+                mode = dsp
+                monitor = true
+                position = preserve
+            }
+        }
+    }
+]
+```
+
+Multiple devices can be created by creating different files in the directory.
+
+If the null sink is only needed temporarily (until the next restart) the following line can be used
+to create it.
+Use different `sink_name`s to create multiple dummy devices.
+
+```sh
+pactl load-module module-null-sink media.class=Audio/Sink sink_name=null-sink-0 channel_map=stereo
+```
+
+This will return an id that can be used to remove the sink with the following command.
+
+```sh 
+pactl unload-module <id>
+```
+
+#### Creating a Device Loopback
+
+In this section a device loopback is defined as a loopback that takes a device as input.
+This can be useful to listen to input devices, such as audio interfaces with connected microphones,
+instruments, etc.
+
+The source for this section of the entry is derived by
+[Pipewire Gitlab site](https://gitlab.freedesktop.org/pipewire/pipewire/-/wikis/Virtual-Devices#single-nodes)
+and [the official website](https://docs.pipewire.org/page_module_loopback.html).
+
+A device loopback can be created permanently by creating a `.conf` file inside the
+`~/.config/pipewire/pipewire.conf.d` directory with the following lines.
+
+```txt
+context.modules = [
+  {
+    name = libpipewire-module-loopback
+    args = {
+      audio.position = [ FL FR ]
+      capture.props = {
+        media.class = "Stream/Input/Audio"
+        node.name = "device-loopback-1-recording"
+        node.description = "Device-Loopback 1 Recording"
+      }
+      playback.props = {
+        media.class = "Stream/Output/Audio"
+        node.name = "device-loopback-1-playback"
+        node.description = "Device-Loopback 1 Playback"
+      }
+      audio.volume = 0.5
+      audio.mute = true
+    }
+  }
+]
+```
+
+The created device loopback is made up by two parts that can be found in different places inside a
+mixer like [pavucontrol](#volume-control).
+The part called `Device-Loopback 1 Recording` in the example config can be found in the `Recording`
+tab.
+There the device to loopback can be selected.
+The second part called `Device-Loopback 1 Playback` is available under the `Playback` tab and
+allows to switch the selection of the output device.
+
+#### Creating an Application Loopback
+
+This section will focus on the creation of an application loopback.
+In this section an application loopback is defined as a loopback that takes an application as input.
+This can be useful to record applications as their sound can cleanly be passed to the sink sink of
+the applicatino loopback which will eliminate other applications sounds.
+If the goal is to record and not listen to the application at the same time navigate to
+[the null device section](#creating-a-null-device).
+Alternatively the null device can also be selected as a output device for the playback part of the
+application loopback which makes it easily and seemlessly possible to switch between listening in
+and not listening without changing the device that is recorded by the capturing program.
+
+The source for this section of the entry is derived by
+[Pipewire Gitlab site](https://gitlab.freedesktop.org/pipewire/pipewire/-/wikis/Virtual-Devices#single-nodes)
+and [the official website](https://docs.pipewire.org/page_module_loopback.html).
+
+An application loopback can be created permanently by creating a `.conf` file inside the
+`~/.config/pipewire/pipewire.conf.d` directory with the following lines.
+
+```txt 
+context.modules = [{
+    name = libpipewire-module-loopback
+    args = {
+        audio.position = [ FL FR ]
+        capture.props = {
+            media.class = "Audio/Sink"
+            node.name = "application-loopback-1-sink"
+            node.description = "Application-Loopback 1 Sink"
+        }
+        playback.props = {
+            media.class = "Stream/Output/Audio"
+            node.name = "application-loopback-1-playback"
+            node.description = "Application-Loopback 1 Playback"
+        }
+    }
+}]
+```
+
+The created device loopback is made up by two parts that can be found in different places inside a
+mixer like [pavucontrol](#volume-control).
+The part called `Application-Loopback 1 Sink` in the example config can be found in the `Output
+Devices` tab.
+The second part called `Application-Loopback 1 Playback` is available under the `Playback` tab and
+allows to switch the selection of the output device.
+Also in the `Playback` tab `Application-Loopback 1 Sink` can be selected as an output for currently
+running applications which will loopback the sound to the selected output device.

wiki/linux/pulseaudio.md

@@ -6,8 +6,10 @@
 
 ## Usage
 
+This section will discuss the usage of PulseAudio.
+
 ### Mixing
 
 For simple sound processing in the form of volume adjustment as well as setting
-the default input and output devices `pavucontrol` can be used as a simple
-mixer.
+the default input and output devices [`pavucontrol`](/wiki/linux/pipewire.md#mixing) can be
+used as a simple mixer.

wiki/linux/qt.md

@@ -0,0 +1,27 @@
+# Qt
+
+[Qt](https://www.qt.io/) is an application and widget toolkit.
+
+## Setup
+
+On most linux distributions different Qt versions are installed as a dependency of various programs
+that use graphical user interfaces.
+
+### Configuration
+
+The configuration can easily be achieved by using the programs
+[qt5ct](https://github.com/desktop-app/qt5ct) or [qt6ct](https://github.com/trialuser02/qt6ct)
+the latter working with the current version of Qt.
+qt5ct is officially archived and qt6ct is the recommended program to use and will mainly be
+discussed in this article.
+These programs can sometimes be found as [package](/wiki/linux/package_manager.md) of the same
+name.
+Afterwards `qt6ct` can be run to get a graphical user interface to set the theme and icons of Qt
+applications.
+This will create or edit a configuration file located at `~/.config/qt6ct/qt6ct.conf`.
+To make this config apply for all Qt applications the following line needs to be inserted into the
+`~/.profile` file.
+
+```sh
+export QT_QPA_PLATFORMTHEME="qt6ct"
+```

wiki/linux/shell.md

@@ -26,6 +26,12 @@ This section addresses various different functions by and actions that can be
 taken with shell commands.
 The focus is mostly on POSIX-compliant shells and scripts that are compatible with POSIX.
 
+A helpful resource for shell scripts is
+[the pure sh bible](https://github.com/dylanaraps/pure-sh-bible).
+There are similar repositories and resources for functions that are outside the scope of POSIX
+shells.
+Because of that and their issue regarding compatibility they will not be mentioned here.
+
 ### Symbolic Links using `ln`
 
 `ln` is a command to create links between files and folders.

wiki/linux/systemd.md

@@ -43,7 +43,7 @@ Alternatively it can be enabled to start at every boot by running:
 sudo systemctl enable unturned
 ```
 
-## Start/Stop/Enable/Disable a service
+### Start/Stop/Enable/Disable a service and Retrieve its Logs
 
 Services can be started by running `systemctl start <service-name>`.
 They respectively can be stopped by replacing the `start`
@@ -51,3 +51,15 @@ keyword for `stop`.
 To start the service after boot it has to be enabled.
 This works accordingly with the keyword `enable`.
 The `disable` keyword stops the service from starting automatically.
+
+Logs of the last start of the service can be found by running `systemctl status <service-name>`. 
+
+### Retrieving the SystemD Logs
+
+SystemD logs can easily be found using the `journalctl` command.
+One of the most notable usages of the command is for checking the logs of the previous boot.
+This can be achieved by running the following command.
+
+```sh
+journalctl -b-1
+```

wiki/linux/tar.md

@@ -0,0 +1,16 @@
+# tar
+
+tar is a package that acts a an archiving utility.
+
+## Usage
+
+This section addresses the usage of the tar package.
+
+### Uncompressing a tar Archive
+
+A tar archive (`.tar`, `.tar.gz`, etc.) can be uncompressed by running the following command.
+In this command `<tar archive>` stands in as a placeholder for the path of the tar archive. 
+
+```sh 
+tar -xf <tar archive>
+```

wiki/linux/watson.md

@@ -0,0 +1,57 @@
+# Watson
+
+[Watson](https://tailordev.github.io/Watson) is a free and open-source time-tracker for
+[Linux](/wiki/linux.md) that uses the [command-line interface](/wiki/linux/shell.md).
+
+## Setup
+
+On most Linux distributions Watson can be installed with the `watson` package.
+Additionally Watson can be installed using Pythons pip package manager.
+The pip package is called ´td-watson`.
+Alternatively it can be installed via [GitHub](https://github.com/TailorDev/Watson).
+
+## Usage
+
+The following section describes various ways of usage of Watson.
+
+### Tracking Time and Displaying Tracked Time
+
+Time can be tracked by running the following command.
+This example tracks time to a project called `world-domination` and uses the tag `cats` and `dogs`.
+Additional tags can be appended or tags can be ommited if not needed.
+This should be adapted to specific needs.
+
+```sh
+watson start world-domination +cats +dogs
+```
+
+Alternatively the start time can be set in the past by adding the `--at` flag with a time.
+
+```sh
+watson start world-domination +cats +dogs --at 13:37
+```
+
+The tracking of the time can be stopped by running the following command.
+
+```sh
+watson stop
+```
+
+Afterwards the summary of the tracked time can be displayed by running the following command.
+
+```sh
+watson report
+```
+
+### Adding a Time Frame in Retrospect
+
+It can be useful to add time frames in retrospect if the starting and stopping of that task was
+forgotten at that time.
+For this the following command can be run.
+It works similarly to starting a time frame as explained in the
+[section above](#tracking-time-and-displaying-tracked-time).
+Additionally the start and stop time are specified with the `--from` and `--to` flags.
+
+```sh
+watson add --from "2018-03-20 12:00:00" --to "2018-03-20 13:00:00" programming +addfeature
+```

wiki/linux/x_window_system.md

@@ -151,3 +151,36 @@ This usually means that either the [Nvidia](/wiki/nvidia.md) kernel module is no
 This can be fixed by [installing Nvidia](/wiki/linux/nvidia.md#setup).
 If this is not the problem then the [initial ramdisk](/wiki/linux/mkinitcpio.md) should be
 [regenerated](/wiki/linux/mkinitcpio.md#manually-generate-initial-ramdisk).
+
+### File Picker Doesn't Work
+
+If the file picker doesn't work in applications like [Discord](/wiki/discord.md) for example first
+check if the desktop portal is installed.
+For that search for the package `xdg-desktop-portal` or a similar named one using your
+[package manager](/wiki/linux/package_manager.md).
+If it is installed check if it starts up correctly by using the command
+`systemctl --user status xdg-desktop-portal` as described in the
+[SystemD entry](/wiki/linux/systemd.md#startstopenabledisable-a-service-and-retrieve-its-logs).
+
+A possible error is `cannot open display` as it was described and fixed by rockzombie2 and V1del in
+an [Arch Linux](/wiki/linux/arch-linux.md)
+[forum post](https://bbs.archlinux.org/viewtopic.php?id=294808).
+To fix this you can run the following commands to temporarily make the file picker work.
+
+```sh 
+systemctl --user import-environment DISPLAY XAUTHORITY
+systemctl --user restart xdg-desktop-portal
+```
+
+If that works make sure the Xorg configs are sourced for users aswell.
+It is possible that the following code block is missing in the local `.xinitrc`.
+This would create similar errors to the ones experienced.
+
+```sh
+if [ -d /etc/X11/xinit/xinitrc.d ] ; then
+    for f in /etc/X11/xinit/xinitrc.d/?*.sh ; do
+        [ -x "$f" ] && . "$f"
+    done
+    unset f
+fi
+```