Fixing Zentyal 2.3 NO_PUBKEY error in apt-get update

Zentyal-2.3 requires following repository, and automatically adds this on your source.list.

 #/etc/apt/source.list.d/zentyal-archive.list

deb http://archive.zentyal.org/zentyal 2.3 main extra

This will automatically be added after you install "zentyal-core" package, or you add the repository using "add-apt-repository".

You will see following error in apt-get update.

W: GPG error: http://archive.zentyal.org 2.3 InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY BE3CB0952C31765E

You can not find any public key for this.

You can fix this by one of followings

- comment out zentyal's repository in source.list (/etc/apt/source.list.d/zentyal-archive.list)

- adding key of "archive.zentyal.org" with following commend if you trust them.

wget http://keys.zentyal.org/zentyal-2.3-archive.asc

sudo apt-key add zentyal-2.3-archive.asc && sudo apt-get update