Before marking this as duplicate, please read the whole question. I've tried all the suggestions in all the related questions I could find, without any success.
I get errors about missing keys for all repos when doing sudo apt update. Running Ubuntu 16.04 LTS.
Get:14 url xenial InRelease [4 731 B]
Err:14 url InRelease
The following signatures couldn't be verified because
the public key is not available: NO_PUBKEY KEY
Deleting and adding the keys manually has no effect at all.
sudo apt-key adv --keyserver keyserver.ubuntu.com KEY1 KEY2 ...
Another related problem that I see is that the Software and Updates app has no entries in the Authentication tab. Which leads me to believe it's an issue related to permissions.
I've checked permissions and compared with what I see is normal online, but can't see anything wrong.
drw-rw-r-- 7 root root 4096 mars 28 09:01 .
drwxr-xr-x 158 root root 12288 mars 28 09:08 ..
drwxr-xr-x 2 root root 4096 mars 28 09:08 apt.conf.d
drwxr-xr-x 2 root root 4096 okt. 5 2015 preferences.d
-rw-r--r-- 1 root root 653 feb. 7 11:22 sources.list
-rw-rw-r-- 1 root root 3100 okt. 12 09:57 sources.list.bak
drw-r--r-- 2 root root 4096 feb. 7 11:23 sources.list.d
drw-r--r-- 2 root root 4096 feb. 1 09:55 sources.list.d.bak
-rw-rw-r-- 1 root root 2902 april 22 2016 sources.list.distUpgrade
-rw-rw-r-- 1 root root 653 feb. 7 11:22 sources.list.save
-rw-r--r-- 1 root root 29811 mars 28 09:01 trusted.gpg
-rw-r--r-- 1 root root 28668 mars 28 09:01 trusted.gpg~
drwxr-xr-x 2 root root 4096 feb. 7 11:22 trusted.gpg.d
I'm stuck now, so any suggestions apart from reinstalling Ubuntu from scratch will be highly appreciated :)
