On my Ubuntu 9.10 system, there's a shadow system group. There does not appear to be any user assigned to this group at all. The only files that I can find belonging to this group are /etc/shadow and /etc/gshadow.

I'm aware that the purpose of these files is to store the passwords separately, out of reach from regular users who still might want to access passwd for other reasons.

But what is the purpose of the shadow group?

The reason I'm curious about this, is because I'm thinking about configuring nsswitch.conf to store it elsewhere, and would like to know if anything is actually trying to access the shadow database using shadow group credentials.