Shared partition permission management

Question

I am willing to try a dual boot arch/lmde setup on my laptop next week, but I've ran into a problem: I want to have a shared data storage where my downloads, documents etc would reside and could be read, written and executed. My first fs of choice was ext4 which needs proper attention with permissions, because like others, between distros, there can be overlapping uids and gids.

So, my question is: Is there any clean way of managing a shared "data" user group across multiple installations, or do I have to settle for a fs which supports the "uid=N gid=N"option?

Answer 1

If you need the shared access for one group only, you'll "just" have to make sure that the group's gid is the same on both systems. (Access rights are granted to the numerical gid/uid, and not to the human-readable name of the group or user.) This is easier if this is a group that is not present by default on at least one of your systems, because you can use the -g switch to groupadd to force the number. (You might be able to change an existing gid by changing it in /etc/group, but then you'd use all access rights previously granted to that group.)

I don't think explicit uid/gid settings when mounting enter into it at all: those exist for file systems which don't have this kind of access control (like vfat), where the owner/group info of files has to be made up.