Set File Access Control Lists (ACLs) in Linux with setfacl
Introduction
The setfacl command in Linux is a powerful tool for setting and managing access control lists (ACLs) on files and directories. ACLs provide a more flexible and granular way to control file permissions compared to the traditional Unix file permissions.
What are ACLs?
ACLs are a way to specify additional permissions beyond the standard owner, group, and other permissions. They allow you to grant specific permissions to individual users or groups, even if they are not the owner of the file or directory.
Using the setfacl Command
To set an ACL on a file or directory, use the following syntax:
setfacl -m [flags] [user:permissions] file_or_directory The following flags are commonly used:
*-m: Modify the existing ACL. * -R: Recursively set ACLs on all files and directories in a directory. * -d: Remove the ACL. The user permissions can be specified in the following format:
*u: User * g: Group * o: Others * a: All * r: Read permission * w: Write permission * x: Execute permission Example
To grant write permission to the user "bob" on the file "my_file", use the following command:
setfacl -m u:bob:rw my_file Verifying ACLs
To verify the ACLs on a file or directory, use the getfacl command:
getfacl file_or_directory Example
getfacl my_file Output: # file: my_file # owner: alice # group: users user::rw user:bob:rw group::r-- other::r-- In this example, the file "my_file" is owned by the user "alice" and is in the group "users". The ACLs grant read and write permissions to the user "bob", read permission to the group "users", and read permission to others.
Conclusion
ACLs provide a powerful way to customize and manage file permissions in Linux. By using the setfacl and getfacl commands, you can easily set and verify ACLs, enhancing the security and flexibility of your file system.
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