dm-crypt: added manual usb key decryption

wiki/linux/dm-crypt.md

@@ -93,3 +93,14 @@ Finally run:
 Reboot the system with `reboot`.
 Make sure the USB key for decryption is plugged in.
 If so the encrypted partition should be decrypted automatically.
+
+## Unlock an encrypted device with the USB key created in the previous section
+
+With the following command an encrypted device can be decrypted with the usb
+stick created in the previous section.
+Make sure to edit `--key-file`, `--keyfile-offset` and `--keyfile-size` to
+match the settings used in the creation of the USB key.
+
+```sh
+cryptsetup luksOpen /dev/sda2 crypt-volume --key-file=/dev/usbkey --keyfile-offset=14848 --keyfile-size=2048
+```

wiki/linux/systemd.md

@@ -0,0 +1,30 @@
+# SystemD
+
+SystemD is a software suit for system components for Linux systems.
+It is mainly used for service configuration.
+
+## Run command on boot
+
+To run a command (in this case `/bin/bash /root/run.sh`) create the following
+file at `/etc/systemd/system/` with a name ending on `.service`.
+In this case it is called `unturned.service`.
+
+```txt
+[Unit]
+Description=Description of the service
+
+[Install]
+WantedBy=multi-user.target
+
+[Service]
+ExecStart=/bin/bash /root/run.sh
+Type=simple
+```
+
+For [Proxmox](./proxmox.md) you can add the following line under the `[Unit]`
+section to make sure the service is started after Proxmox has finished
+initializing.
+
+```txt
+After=pve-guests.service
+```