The Linux permission system isn't complex. It uses three attributes for three different permission positions. Knowing how read, write and execute works on files is important. These same permissions are used for directories too which provides the ability to enter directories, create new files and list directory contents.
- [Instructor] Standard Linux permissions support three different modes, read, write, and execute. These three modes provide different functionality for files and directories. For files, read access means the user can open and read the contents of a file. When a user has write access to a file, they can write or modify the contents. When a user has execute permissions on a file, it means that the file can be run as an application. Commands like LS and applications like Firefox would have their execute bit set.
What happens when a command is executed, is it's loaded into memory and run until told to stop. These same three modes act differently on a directory. If a user has read access to a directory, it means they can list the contents of the directory, which includes the metadata about the files and directories in it. If a user doesn't have read access, and they type in LS inside the directory, you'll see a lot of question marks where the metadata should be. If a user has write access to a directory, it allows them to write to the directory.
Writing to the directory means creating new files in it. Execute permissions on a directory are a bit at odd. You're not going to run a directory like you would a command. Execute permissions means that you can enter or traverse the directory.
- Define file Access Control Lists.
- Describe what extended globs add to Linux pattern matching.
- State why file system recovery tools are so important for Linux users.
- Recall what execute permissions on a directory allows.
- Cite the maximum allowed default permissions on a file in Linux.
- List some of the advantages of ACLs over standard Unix permissions.