Hi, I am using Arch Linux on lots of my personal servers, and most of them are not updated regularly. This causes trouble when I need to install a package on these servers because the requested package versions are already gone from mirrors. Upgrading these machines requires some effort because I need to wait and also manually fix pacnews, so it is not very ad-hoc. This is also an annoying issue on old (well, not the latest I'd say) Arch ISOs. I sometimes use Arch ISO to debug offline Linux systems, and I need to quickly install some debug tools, but my old Arch ISOs usually need to get a full update to install these packages, which is really annoying. Although Arch Linux is currently providing an archive service, it still requires manually typing the URL, which is not very convenient. I would like to work on a patch that automatically falls back to downloading `https://archive.archlinux.org/packages/.all/package_name-version-arch.pkg.tar.xxx` if all mirrors returned 404. The administrator may configure the archive URL prefix in pacman.conf(5). How does that sound? This is only a handy helper for users and will not likely to break any Arch systems except those very old ones, which need to be upgraded to get things working. If it sounds good, I would like to submit the patch as soon as possible, or are there any suggestions? Thank you very much. Best regards, Yuuta Liang