Changed apt installation instructions gpg import (#1845)

apt-key is deprecated and shouldn't be used nor should the trusted keystore in /etc/apt. Instead the gpg keys should be stored somewhere else and the list file that adds the openHAB repo should point at that one key. Thus, apt will only trust that key for that repo instead of trusting that key even if it's used by some other repo.

There were problems with the redirect from `gpg` which makes the command fail sometimes even when using sudo which is why I save it locally and then move and chmod it after.

Signed-off-by: Richard Koshak rlkoshak@gmail.com

installation/linux.md

@@ -69,10 +69,13 @@ Alternatively resort to the [manual installation approach](#manual-installation)
 
 {% include collapsible/body.html %}
 
-First, add the openHAB repository key to your package manager:
+First, add the openHAB repository key to your package manager (note `/usr/share/keyrings` may already exist):
 
 ```shell
-wget -qO - 'https://openhab.jfrog.io/artifactory/api/gpg/key/public' | sudo apt-key add -
+curl -fsSL "https://openhab.jfrog.io/artifactory/api/gpg/key/public" | gpg --dearmor > openhab.pgp
+sudo mkdir /usr/share/keyrings
+sudo mv openhab.pgp /usr/share/keyrings
+sudo chmod u=rw,g=r,o=r /usr/share/keyrings/openhab.pgp
 ```
 
 Then, you can choose between, *Official (Stable)*, *Beta* or *Snapshot* builds:
@@ -84,7 +87,7 @@ Then, you can choose between, *Official (Stable)*, *Beta* or *Snapshot* builds:
     Add the **openHAB Stable Repository** to your systems apt sources list:
 
     ```shell
-    echo 'deb https://openhab.jfrog.io/artifactory/openhab-linuxpkg stable main' | sudo tee /etc/apt/sources.list.d/openhab.list
+    echo 'deb [signed-by=/usr/share/keyrings/openhab.gpg] https://openhab.jfrog.io/artifactory/openhab-linuxpkg stable main' | sudo tee /etc/apt/sources.list.d/openhab.list
     ```
 
 - **Testing Release**
@@ -94,7 +97,7 @@ Then, you can choose between, *Official (Stable)*, *Beta* or *Snapshot* builds:
     Add the **openHAB Beta Repository** to your systems apt sources list:
 
     ```shell
-    echo 'deb https://openhab.jfrog.io/artifactory/openhab-linuxpkg testing main' | sudo tee /etc/apt/sources.list.d/openhab.list
+    echo 'deb [signed-by=/usr/share/keyrings/openhab.gpg] https://openhab.jfrog.io/artifactory/openhab-linuxpkg testing main' | sudo tee /etc/apt/sources.list.d/openhab.list
     ```
 
 - **Snapshot Release**
@@ -106,7 +109,7 @@ Then, you can choose between, *Official (Stable)*, *Beta* or *Snapshot* builds:
     To use it, add the **openHAB Unstable Repository** to your systems apt sources list:
 
     ```shell
-    echo 'deb https://openhab.jfrog.io/artifactory/openhab-linuxpkg unstable main' | sudo tee /etc/apt/sources.list.d/openhab.list
+    echo 'deb [signed-by=/usr/share/keyrings/openhab.gpg] https://openhab.jfrog.io/artifactory/openhab-linuxpkg unstable main' | sudo tee /etc/apt/sources.list.d/openhab.list
     ```
 
 Next, resynchronize the package index: