E: Conflicting values set for option Signed-By regarding source https://apt.postgresql.org/pub/repos/apt/ noble-pgdg: /usr/share/postgresql-common/pgdg/apt.postgresql.org.asc != /usr/share/postgresql-common/pgdg/apt.postgresql.org.gpg
E: The list of sources could not be read.

- What is the error message telling us?
The error message indicates a conflict with the Signed-By option regarding the source https://apt.postgresql.org/pub/repos/apt/. Specifically, it states that the GPG key used to sign the repository (/usr/share/postgresql-common/pgdg/apt.postgresql.org.asc) is different from the one it expects (/usr/share/postgresql-common/pgdg/apt.postgresql.org.gpg).

- This could be due to a few possible reasons:
The GPG key used to sign the PostgreSQL repository has been changed or updated, but the system's configuration has not been updated accordingly.
There is a conflict or issue with the system's package management configuration, potentially caused by other repositories or packages.

- Here is how to go about it. There are several ways to fix it, but I'll give the one that best works for me and is always sure to work.

Steps

- cd into the **sources.list.d directory.**

cd /etc/apt/sources.list.d

- list all the files found in the directory

ls

alexlarsson-ubuntu-flatpak-noble.sources
archive_uri-https_packages_microsoft_com_repos_vscode-noble.list
flatpak-ubuntu-stable-noble.sources
google-chrome.list
hashicorp.list
pgdg.list
pgdg.sources
touchegg-ubuntu-stable-noble.sources
ubuntu-esm-apps.sources
ubuntu-esm-infra.sources
ubuntu.sources
ubuntu.sources.curtin.orig
vscode.list

Note: The list of the files will vary depending on what causes your error to appear. You then need to open the files and delete any file that has to do with gpg. In my case, it was the PostgreSQL files that were causing those errors

- cat the files one after another if you do not know which one to look into in my case I had to delete any file that has to do with gpg in the sources.list.d directory.

cat pgdg.sources

result

Types: deb
URIs: https://apt.postgresql.org/pub/repos/apt
Suites: noble-pgdg
Components: main
Signed-By: /usr/share/postgresql-common/pgdg/apt.postgresql.org.gpg

sudo rm pgdg.sources

cat pgdg.list

result

deb [signed-by=/usr/share/postgresql-common/pgdg/apt.postgresql.org.asc] https://apt.postgresql.org/pub/repos/apt noble-pgdg main

 sudo rm pgdg.list

- After removing all the files, you can now try running the update command or any apt command again.

sudo apt update

result

Hit:1 http://security.ubuntu.com/ubuntu noble-security InRelease
Hit:2 http://archive.ubuntu.com/ubuntu noble InRelease         
Hit:3 https://apt.releases.hashicorp.com noble InRelease       
Hit:4 https://dl.google.com/linux/chrome/deb stable InRelease  
Hit:5 https://esm.ubuntu.com/apps/ubuntu noble-apps-security InRelease
Hit:6 http://archive.ubuntu.com/ubuntu noble-updates InRelease 
Hit:7 https://packages.cloud.google.com/apt cloud-sdk InRelease
Ign:8 https://ppa.launchpadcontent.net/alexlarsson/flatpak/ubuntu noble InRelease
Hit:9 https://esm.ubuntu.com/apps/ubuntu noble-apps-updates InRelease
Hit:10 https://ppa.launchpadcontent.net/flatpak/stable/ubuntu noble InRelease
Hit:11 http://archive.ubuntu.com/ubuntu noble-backports InRelease
Hit:12 https://packages.microsoft.com/repos/vscode stable InRelease
Hit:13 https://esm.ubuntu.com/infra/ubuntu noble-infra-security InRelease
Hit:14 https://ppa.launchpadcontent.net/touchegg/stable/ubuntu noble InRelease
Hit:15 https://packages.microsoft.com/repos/code stable InRelease
Hit:16 https://esm.ubuntu.com/infra/ubuntu noble-infra-updates InRelease
Err:17 https://ppa.launchpadcontent.net/alexlarsson/flatpak/ubuntu noble Release
  404  Not Found [IP: 185.125.190.80 443]
Reading package lists... Done