File Ownership and Permissions
It is important in multi-user system to ensure that files of one user cannot be accessed by another user, until and unless user is permitted to access the files. The user who creates the file, is by default the owner of that file. He can do whatever he wants to do with that file, like editing or deleting or renaming.
If the member of the group has created the file then he can also own that file. User group will have the same permissions as that of file creator. This is a very important feature provided by Linux. Other users can also be granted privileges to the file so that other users can also work on the files created by the owner of the file.
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