If I perform sudo apt-get update. I obtain:
GPG error: http://cdn-fastly.deb.debian.org/debian jessie Release: The following signatures were invalid: EXPKEYSIG 7638D0442B90D010 Debian Archive Automatic Signing Key (8/jessie) <ftpmaster@debian.org> EXPKEYSIG CBF8D6FD518E17E1 Jessie Stable Release Key <debian-release@lists.debian.org> 75DDC3C4A499F1A18CB5F3C8CBF8D6FD518E17E1
E: The repository 'http://http.debian.net/debian jessie Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
How can I fix this?
Thanks for the feedback.
My installed Ubuntu: Distributor ID: Ubuntu Description: Ubuntu 20.04.5 LTS Release: 20.04 Codename: focal
/etc/apt/sources.list
then re-edit that file & remove it. If you added it as a source in/etc/apt/sources.list.d/
then remove that added file. Given Debian jessie has been EOL since 30-June-2020 - you've likely only added it recently (~2.5 years living with that message makes me think it was recent). – guiverc Jan 05 '23 at 10:54