' stable/updates Release' no longer has a Release file (apt update error on ubuntu 21.04)

ar flag

On a Ubuntu 21.04 the sudo apt update command generates console ouput as follows:

barium@berta$ sudo apt update
Ign:3 stable/updates InRelease                                
Err:4 stable/updates Release                                  
  404  Not Found [IP: 2a04:4e42:6c::644 80]
Hit:9 hirsute-security InRelease
Reading package lists... Done
E: The repository ' stable/updates Release' no longer has a Release file.
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.

Manual changes to the Ubuntu Software & Updates Manager produce the same error message.

The /etc/apt/sources.list contains among others the following deb statements:

barium@berta$ cat /etc/apt/sources.list
deb hirsute-security main restricted
deb hirsute-security universe
deb hirsute-security multiverse

In an answer to a similar post it was suggested to replace '' and '' with ''. That didn't work.

user535733 avatar
cn flag
Is the use of Debian sources on your system intentional?
ar flag
Normal Ubuntu installations do not have Debian Security repositories. Try removing the lines with `` in the `/etc/apt/sources.list` as well as files in the folder `/etc/apt/sources.list.d` that refers to Debian.
guiverc avatar
cn flag
Your system is likely not a Ubuntu one; as the post you provided applies on with a Debian install. If it was added to a Ubuntu install; you may no longer be using Ubuntu as `apt` & `dpkg` cannot tell which packages are foreign or local - they upgrade to the latest available in the sources. It looks to me that you're using a Debian system & not a Ubuntu one. `ubuntu-security-status` may provide some clues but I'd explore what you were running, and what you're now running as it may be neither - a *frakensystem* with bits of both & no longer either Ubuntu or Debian.
karel avatar
sa flag
Does this answer your question? [What can I do if a repository/PPA does not have a Release file?](
ar flag
So far I assumed the debian packages were called implicitly by the ubuntu one's. According to your answers that shouldn't be the case so I checked the sources.list file again, but found no line containing a debain package. Might there be multiple sources.list files and if so where or how will I find them? In sources.list.d and elsewhere?
ar flag
Furthermore If I make changes to these files, removing the debian repos, is there any danger of corrupting the system?
ar flag
The machine I am working on is an Ubuntu system, but some automatization magic run on it, in order to setup many different tools that I (obviously) don't comprehend.

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