linux: added display managers and plymouth

wiki/linux/display_managers.md

@@ -0,0 +1,28 @@
+# Display Managers
+
+Display managers are graphical user interfaces that is displayed after booting.
+Usually it also manages the login process before starting the window manager.
+
+## List of Display Managers 
+
+The following display managers are featured in this wiki.
+
+- [LightDM](/wiki/linux/lightdm.md) is a lightweight GUI display manager.
+- [Lemurs](/wiki/linux/lemurs.md) is a lightweight TUI display manager.
+
+## Use `xinitrc` as `xsession`
+
+Often a display manager needs a `xsession` to work.
+For this `init-xsession` needs to be installed which is available on most
+[Linux distributions](/wiki/linux.md#distributions) in a package of the same name.
+When setting this up there should be no `~/.xsession` available.
+If it is please use another setup or backup this file.
+Make the `xinitrc` file executable as shown in the following command and link it to the `xsession` 
+file.
+
+```sh
+chmod +x ~/.xinitrc
+ln -s ~/.xsession ~/.xinitrc
+```
+
+Afterwards the session will start like the `xinitrc`

wiki/linux/lemurs.md

@@ -0,0 +1,31 @@
+# Lemurs
+
+[Lemurs](https://github.com/coastalwhite/lemurs) is a lightweight TUI
+[display manager](/wiki/linux/display_managers.md).
+It is available for both [X](/wiki/linux/x_window_system.md) and Wayland.
+
+## Setup
+
+On most linux distributions LightDM can be installed with the `lemurs` package.
+
+This setup needs an `xsession`.
+An alternative to this is using `xinitrc` as an `xsession`.
+The process of this is desribed in the
+[display manager entry](/wiki/linux/display_managers.md#use-xinitrc-as-xsession).
+Make sure to have a working `xsession` or `xinitrc`.
+If you are not sure about it, use the tests provided in the penultimate step.
+
+Before finishing the setup the functionality should be tested.
+This can be done by using one or both of the following commands. 
+
+```sh 
+systemctl start lemurs.service
+```
+
+Finally the [SystemD](/wiki/linux/systemd.md) lightdm service needs to be enabled and reboot the
+system.
+
+```sh 
+systemctl enable lemurs.service`
+reboot
+```

wiki/linux/lightdm.md

@@ -0,0 +1,40 @@
+# LightDM
+
+[LightDM](https://github.com/canonical/lightdm/) is a lightweight GUI
+[display manager](/wiki/linux/display_managers.md).
+It is available for both [X](/wiki/linux/x_window_system.md) and Wayland.
+
+## Setup
+
+On most linux distributions LightDM can be installed with the `lightdm` package.
+Additionally `lightdm-gtk-greeter` and `xorg-server-xephyr` are recommended.
+
+This setup needs an `xsession`.
+An alternative to this is using `xinitrc` as an `xsession`.
+The process of this is desribed in the
+[display manager entry](/wiki/linux/display_managers.md#use-xinitrc-as-xsession).
+Make sure to have a working `xsession` or `xinitrc`.
+If you are not sure about it, use the tests provided in the penultimate step.
+
+Then edit the config file `~/.dmrc` and edit the file to the following contents.
+
+```txt 
+[Desktop]
+Session=xinitrc
+```
+
+Before finishing the setup the functionality should be tested.
+This can be done by using one or both of the following commands. 
+
+```sh 
+lightdm --test-mode --debug
+systemctl start lightdm.service
+```
+
+Finally the [SystemD](/wiki/linux/systemd.md) lightdm service needs to be enabled and reboot the
+system.
+
+```sh 
+systemctl enable lightdm.service`
+reboot
+```

wiki/linux/plymout.md

@@ -0,0 +1,34 @@
+# Plymouth 
+
+[Plymouth](https://www.freedesktop.org/Software/Plymouth) is a software that provides a better
+graphical boot process.
+It can change the native resolution early in the boot process and display splash screens.
+
+## Setup
+
+On most linux distributions LightDM can be installed with the `plymouth` package.
+
+Afterwards the kernel options need to be changed.
+On [Arch Linux](/wiki/linux/arch-linux.md) systems this can be done by editing the file located at
+`/boot/loader/entries/arch.conf`.
+In the options line append `quiet` if you want to use the quiet-mode and `splash` if you want to 
+add a splash screen.
+
+If the splash screen option was selected edit the file `/etc/plymouth/plymouthd.conf` and ensure it
+looks like the following lines.
+
+```txt
+[Daemon]
+Theme=fade-in
+```
+
+Then inside the file `/etc/mkinitcpio.conf` add the hook under the `HOOKS` section.
+Add `plymouth` after `systemd` (if available) and before `encrypt` and `lvm2` (if available.)
+
+Finally regenerate the initial ramdisk as described
+[in the mkinitcpio entry](/wiki/linux/mkinitcpio.md#manually-generate-initial-ramdisk).
+For this run the following command.
+
+```sh
+mkinitcpio -p linux
+```

wiki/linux/x_window_system.md

@@ -10,6 +10,12 @@ It is maintained by the [X.Org Foundation](https://x.org/wiki/).
 
 This section addresses various usages of the X Window System.
 
+### Display Managers
+
+[Display managers](/wiki/linux/display_managers.md) are user interfaces displayed after booting.
+They are featured in a [separate entry](/wiki/linux/display_managers.md).
+This also includes any configuration needed for it like `xsession`.
+
 ### Screen Locker
 
 The X Window System allows various screen lockers to be used.