A while ago, I set up unattended-upgrades on my Debian 13 machines. Running sudo apt updatedoesn’t cross my mind now that I assume unattended-upgrades takes care of that for me, but every once in a while, I’ll try installing something and get the “Unable to locate package” errors associated with outdated repositories. After being made aware of having outdated repositories and packages, I’ll go and run sudo apt update && sudo apt upgrade on my other machines, only to be told that all packages are up to date and unattended-upgrades did do its job there. I don’t keep a record of this happening, but I also don’t recall there being any pattern to which of my machines are affected and which aren’t at any given time.
Where could I start hunting down the cause of this inconsistent behavior? I did double-check that I enabled it via sudo dpkg-reconfigure unattended-upgrades
I think unattended-upgrades only runs once a day by default, and the repository index could have changed since then. Different results on different machines can be because unattended-upgrades didn’t run at the same time, or from the same mirror (and mirrors take a while to propagate changes). Generally speaking you should always run an apt update directly before installing new packages.