linux filesystem kernel module/chrooting/xfs/etc.

[Harald Barth]

Would it be any problem to have something like

/users/bob/tools/bin/...
/users/bob/tools/lib/...
/users/bob/data/...
/users/phil/tools/...
/users/phil/data/...

bob is mount point for volume users.bob
phil is mount point for volume users.phil
tools is mount point for common.tools
tools has permissons that are read-only for users bob and phil

This requires that you have something like AFS volumes or fake such a
thing (loopback mounts?). With AFS volumes you can have thousands of
mountpoints. I doubt loopback mounts fix that. Hope I didn't
misunderstand your question.

Harald.