File Access
File restrictions and file access are common place for almost any company that operates with any sort of database / file management system. In this case we have 5,000 users, but only want to allow 4,990 of those user to access a certain file. Of course that first that that pops into the minds of most database administrators would be grouping. Of course just saying that does not mean that it is that simple of a task. There are also other variables that must be taken into account. Someone has to be the "owner" of the file, and we could assume that a certain amount of users will need to be able to edit the file. So even though we have a group set up for this file, there are other layers of groups that would need to be considered. So then you think maybe just restrict the 10 left over users from that file, sounds like a simple solution. But then you still run into problems with file ownership and editing ability.
According to Stallings (2012), most UNIX systems depend on, or at least are based on, the file access control scheme introduced with the early versions of UNIX. Each UNIX user is assigned a unique user identification number (user ID). A user is also a member of a primary group, and possibly a number of other groups, each identified by a group ID. When a file is created, it is designated as owned by a particular user and marked with that user’s ID. It also belongs to a specific group, which initially is either its creator’s primary group, or the group of its parent directory if that directory has SetGID permission set. Associated with each file is a set of 12 protection bits. The owner ID, group ID, and protection bits are part of the file’s inode.