Understanding users, groups, and basic permissions
Multi-user environments are defined by being able to handle more than one user simultaneously. But to be able to administer the system resources, two capabilities help with the tasks:
- Groups: Can aggregate users and provide permissions for them in blocks.
Each user has a primary group.
By default, a group is created for each user and assigned to it as a primary with the same name as the username.
- Permissions: Assigned to files, determining which users and groups can access each file.
Standard Linux (and UNIX or POSIX) permissions include user, group, and others (ugo).
The whole system comes with a set of permissions assigned by default to each file and directory. Be careful when changing them.
There is a certain principle in UNIX that Linux has inherited: everything is a file. Even when there may be some corner cases to this principle, it remains true on almost any occasion. It means that a disk...
