November 24, 2014
The file system in UNIX enables a person to control which users can have access to your files and directories and the types of access modes that are allowed. Even though the file protection in UNIX is really easy, it is a really good thing to have in most situations. The protection is pretty much the same for the files and directories. The UNIX system has three types of access modes: read, write, and execute. A person has to have read access to read what is in a file. A person must have write access to change the data in the files. A person also has to have execute access to run the file. These three modes are independently operated, so having write access does not indicate read access.
If I had a system that supports 5000 users and I only wanted to allow 4990 of the users to be able to access one file I would put each of the users into groups and create certain passwords for each of the groups. To maintain which users have which access rights, each file or directory should have an owner and a group. A file or directory can only have one person who owns it and they also own anything that is created. The group is just the list of names of the people who can have access to the files or directories. In a system that supports 5000 users, the system administrator would be the person who makes the groups and assign the users to them. A file or directory can only