As we know Linux is the multi-user operating system it means that Linux system can use several users at the same time. For that reason, you are allowed to use Linux in mainframes and servers without any modifications. But there are certain issues related to security. For example, one user can modify or delete files and directories which belong to another user. To solve this problem in Linux system authorization was divided into two levels.
- Ownership (user groups)
there are 3 types of user groups:
Owner - by default person who creates some file or directory becomes its owner. Files with owner permission can change only owners of that files.
Group – here are several users who can work with that file. users in this group will have the same permissions.
All users or Other – in this group will be included all other users. users in this group can also create some files or directories or belong to some other group.
each of this groups have permissions. There is three type of permissions:
Read permission – it means that you can only open and read that file
Write permission – you are allowed to modify the file. this permission gives you the ability to add, rename or remove the file.
Execute permission - in Windows OS all executable files have “.exe” extension and you can easily execute them with double click on them. But here you can do that without execute permission. Even if you have Read and Write permissions you can only read the code of that file and modify that but not execute.
Here are shown how you can understand permissions each of group:
The first “-” means that it is some file and “d” means there is some directory.
The next three symbols are permissions of the owner or user then group permission and the last is other users permissions. Here is what you need to know to start to discover the permissions in Linus system.