[SOLVED] Sources List Problem NO PUBKEY

[mhumm2]

This is strange. I tried:

$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys KEY_ID 2836CB0A8AC93F7A

But it did not work. I commented out one source at a time to narrow down which source was causing the problem. I now have all my sources commented out and I'm still getting the following terminal print out:

$ sudo apt-get update
Get:1 http://ppa.launchpad.net/kubuntu-ppa/beta/ubuntu bionic InRelease [20.7 kB]
Err:1 http://ppa.launchpad.net/kubuntu-ppa/beta/ubuntu bionic InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2836CB0A8AC93F7A
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net/kubuntu-ppa/beta/ubuntu bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 2836CB0A8AC93F7A
E: The repository 'http://ppa.launchpad.net/kubuntu-ppa/beta/ubuntu bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

Here is a print out of my /etc/apt/sources.list

# deb cdrom:[Kubuntu 18.04 LTS _Bionic Beaver_ - Release amd64 (20180426)]/ bionic main multiverse restricted universe

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
# deb http://us.archive.ubuntu.com/ubuntu/ bionic main restricted

## Major bug fix updates produced after the final release of the
## distribution.
# deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
# deb http://us.archive.ubuntu.com/ubuntu/ bionic universe
# deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
# deb http://us.archive.ubuntu.com/ubuntu/ bionic multiverse
# deb http://us.archive.ubuntu.com/ubuntu/ bionic-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://us.archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu/ bionic partner

# deb http://security.ubuntu.com/ubuntu/ bionic-security main restricted
# deb http://security.ubuntu.com/ubuntu/ bionic-security universe
# deb http://security.ubuntu.com/ubuntu/ bionic-security multiverse

So what source is my system attempting to update when they're all commented out?

[kubicle]

This is strange. I tried:
$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys KEY_ID 2836CB0A8AC93F7A

You're supposed to replace the "KEY_ID" with the actual key ID, so the correct command should be:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 2836CB0A8AC93F7A

So what source is my system attempting to update when they're all commented out?

Probably a ppa source that is defined in a file in /etc/apt/sources.list.d/ directory

[mhumm2]

Kubical,

Yep, you were right on both counts. Thanks so much.

[jlittle]

So what source is my system attempting to update when they're all commented out?

I see the problem is solved, but for completeness...

You checked /etc/apt/sources.list, but did you look in the directory /etc/apt/sources.list.d? Files in there that match *.list or *.sources are processed as well as /etc/apt/sources.list.