Using setfacl (with examples)

Modify ACL of a file for user with read and write access:

Code:

setfacl -m u:username:rw file

Motivation: The motivation behind modifying the ACL of a file for a specific user is to grant that user the ability to read and write to the specified file. By using the setfacl command with the -m option, we can easily modify the ACL of a file and set specific permissions for a user.

Explanation:

• setfacl: The command used to set file access control lists (ACL).
• -m: The option used to modify the ACL of a file.
• u: The identifier for a user permission entry.
• username: The name of the user for whom we want to modify the ACL.
• rw: The permissions we want to assign to the user. “r” represents read access, and “w” represents write access.
• file: The path to the file whose ACL we want to modify.

Example Output: The ACL of the file “file” is modified to grant the user “username” read and write access.

Modify default ACL of a file for all users:

Code:

setfacl -d -m u::rw file

Motivation: The motivation behind modifying the default ACL of a file for all users is to set the default permissions that will be applied to all new files and directories created within the specified file’s directory. By using the setfacl command with the -d option, we can modify the default ACL and ensure that the specified permissions are automatically inherited by all future files and directories.

Explanation:

• -d: The option used to modify the default ACL of a file.
• u::rw: The default permission entry for all users. The empty “u:” specifies that this permission entry applies to all users. “rw” represents read and write access.
• file: The path to the file whose default ACL we want to modify.

Example Output: The default ACL of the file “file” is modified to grant all users read and write access. Any new file or directory created within the same directory as “file” will inherit these permissions.

Remove ACL of a file for a user:

Code:

setfacl -x u:username file

Motivation: The motivation behind removing the ACL of a file for a specific user is to revoke any permissions that were previously granted to that user. By using the setfacl command with the -x option, we can easily remove a specific user’s permission entry from the ACL of a file.

Explanation:

• -x: The option used to remove a specific user’s permission entry from the ACL of a file.
• u:username: The identifier for the user permission entry we want to remove.
• file: The path to the file whose ACL we want to modify.

Example Output: The ACL of the file “file” is modified, removing the permission entry for the user “username”.

Remove all ACL entries of a file:

Code:

setfacl -b file

Motivation: The motivation behind removing all ACL entries of a file is to completely reset the file’s ACL and remove any specific permissions that were previously assigned. By using the setfacl command with the -b option, we can easily remove all ACL entries from a file.

Explanation:

• -b: The option used to remove all ACL entries from a file.
• file: The path to the file whose ACL we want to modify.

Example Output: The ACL of the file “file” is modified, removing all permission entries. The file will now only inherit the default permissions from its parent directory.