Differences between UID 0 and GID 0?

dwarf007 · 02-24-2010, 02:59 AM

Anyone knows the differences between UID 0 and GID 0?

business_kid · 02-24-2010, 03:14 AM

uid=user id
gid=group id.

Each uid is unique on a system (usually) but gids(=groups) can have many uids(=users) in them

vinaytp · 02-24-2010, 04:02 AM

Quote:

Originally Posted by dwarf007

Anyone knows the differences between UID 0 and GID 0?

UID 0 refers to root's user ID.
GID 0 refers to group ID of the group root.

When the user account root is created by the system, group root will also be created at the same time with root as a single user in the group root.

You can add your username to root group, provided if you have previliges to do so.

dwarf007 · 03-15-2010, 09:37 PM

Does it mean UID 0 and GID 0 have the same privilege?

pixellany · 03-15-2010, 09:47 PM

Quote:

Originally Posted by dwarf007

Does it mean UID 0 and GID 0 have the same privilege?

No!!
Privileges are assigned to users and to groups independently.

Look at the definition of privileges: There are 3 levels: owner, group, and others. The get the owner privileges, you need to be the owner. To get the group privileges, you need to be a member of the group.

frieza · 03-15-2010, 10:00 PM

actually uid 0 and gid 0 are arbitrary just as the accout name root, however standard on almost all unix/unix like systems
it would theoretically be possible to change the uid and gid of root to something else, albeit probably more difficult then it's worth

business_kid · 03-16-2010, 04:52 AM

@dwarf007: Read man chmod - that explains the permission system