On Wed, Dec 18, 2019 at 1:55 PM Neil Bothwick <n...@digimed.co.uk> wrote: > > On Wed, 18 Dec 2019 19:24:03 +0100, tu...@posteo.de wrote: > > > What is the mechanism and how does it work, which > > cares, that a certain package of a certain version > > gets installed only once? > > The package database is at /var/db/pkg >
It is probably worth noting that there really isn't anything preventing a package from being re-installed over the same version of itself. Portage shouldn't generally try to do this unless there is some reason to rebuild it (slot op dep change/etc). However, you can force it to do so (harmlessly) at any time just by running emerge -1 <atom>. In general when a package is installed and another package exists in the same slot (whether the same version or not), first portage installs the new package, and then it removes the old version. However, portage tracks files by hash and modification date so when it goes to remove the old package, any files that were overwritten by the new package will no longer match, and thus will not be removed. Any files installed by the old version which were not overwritten by the new version (which could be the same version) will get removed. This also allows updates to system/toolchain/etc packages in-place without too much disruption to running processes (obviously already open files are unaffected regardless due to unix mechanics, but you could get race conditions with files that aren't actually open if it were done the other way around). -- Rich
