Suppose a multiboot computer on which two GNU/Linux distributions are installed, each with its own user(s). Say those users don't share the same UID over the two systems.
Now one needs to access the user-owned files of the first system from the second.
I can think of a few methods (obviously by root or sudo, or by group, or by a dedicated user with same UID, or change owner (!), or switch user to numeric ID (but I don't think it is possible ?)…), each having its drawbacks.
Is there a recommended way to access such files ?
Note that the question is slightly broader than accessing files owned by a different user on the same system (actually this would correspond to the "dedicated user with same UID" solution), since in our case the UID does not correspond to a user.
Note also that there may be several users (and therefore multiple UIDs) on each system. User C on the second system may need to access files from both users A & B on the first system.