[Mashiro]

Error 404 (Not Found) means that the file(s) or folder(s) that the APT package manager was looking for are no longer existing on the server.

And the current situation on the server is indeed how the error describes it. The directory "jessie-updates" doesn't exist on that Debian package server mirror. There is only the folder "jessie".


The reason for that is most likely that Jessie has become "Oldstable" now. Meaning it is being kind of archived as Debian "Stretch" 9 is the latest stable Distro. What that means... of course they're reorganizing the mirror servers.

You need to update your /etc/apt/sources.list with new mirrors from https://pastebin.com/RBQV42Uh