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setfacl Command in Linux

setfacl Command in Linux

By Team Scaler
2 mins read
Last updated: 31 Dec 2023
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Overview

The 'setfacl' command in Linux, an abbreviation for 'set file access control lists', is a powerful tool that allows users to manage specific permissions for multiple users and groups on a file or directory. Unlike traditional chmod permissions, the setfacl command in Linux allows for much finer control over who can access a file and what they can do with it.

Syntax of setfacl Command in Linux

The basic syntax of the setfacl command in Linux is as follows:

Where:

  • acl_spec: This is the ACL specification that you want to modify. It follows the format of 'user:name', 'group:name', or 'other'.
  • acl_file: This is a file from which to restore ACLs. It is used with the '-M' or '-X' flags.
  • file: This is the file or directory that you want to modify ACLs on.

Options in setfacl Command in Linux

  1. -m: Modify the ACL of a file or directory

    For example -

    This command adds read, write, and execute permissions for the user 'user' to the file 'file'.

  2. -x: Remove specified ACL entry

    For example -

    This command removes all permissions for the user 'user' from the file 'file'.

  3. -b: Remove all ACL entries

    For example -

    This command removes all ACL entries from the file 'file'.

Example Usages

  • Adding user permissions to a file:

    Explanation: This command adds read permission for the user 'user' to the file 'file'.

  • Removing all ACL entries from a file:

    Explanation: This command removes all ACL entries from the file 'file'.

Tips

  • Be careful when removing ACL entries with '-b' or '-x', as you cannot recover them afterwards.

  • If you need to apply the same ACL to many files, consider using the '-R' option to apply ACLs recursively.

Advanced Use Cases of setfacl Command in Linux

  • Using the setfacl command in Linux with mask:

    Explanation: The 'm' ACL sets the maximum permissions for all users, groups, and others. This command sets the mask to read-only.

  • Setting default ACL entries:

    Explanation: This command sets the default ACL entry for the user 'user' to read and write on the file 'file'. Any files created within the directory 'file' will inherit these permissions.

  • Restoring ACL entries from a file:

    Explanation: This command restores the ACLs for the file 'file' from the 'acl_file'.

Conclusion

  • The setfacl command in Linux provides fine-grained control over file and directory permissions.

  • With setfacl, you can manage permissions for multiple users and groups, far beyond what is possible with traditional chmod permissions.

  • While powerful, careful usage of setfacl is required, as you cannot recover ACL entries after removing them.