Redhat7:users

Introduction to Users and Groups

While users can be people or applications, groups are a logical means of organizing users. Each member of a group can read write of execute files that are owned by the group. Each User is assigned a UID, and each group is assigned a GID.

The root user can change the owners and permissions as well as the files owner.

In addition redhat provides Access Control lists (ACLs) which allow for user specific permissions to be applied

User Private Groups

Whenever a user is created, a group of the same name is also created. This is the User Private group, of which that user will be the only member. The UPG allows default permissions to be applied safley as the user and the users UPG can modify their files. This is because the default permissions are usually 755.

Shadow Passwords

In a system with multiple users shodow passwords should be used to increase security. Each password is encrypted and stored in the /etc/shadow file which is only readble by the root user.