Getting stuff done in Ubuntu - permissions and security

Linux security is done by giving every file or directory (folder) an owner and a group.
During the startup process, you will be asked to login with a username and password. The administrator (root) will have set their password during installation.
If you are not the owner of a file, you will not be able to access it unless the owner has allowed one of your groups to do so.
The administrator ("root") sets up groups with the Users Administration Tool (User settings).
For each file, a group can be set and what the group can do with the file (Read and write, Read only or None).
The owner of a file is set as the logged-in user, the owner can be changed at command-line level.


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