Which command revokes ACL-based write access for groups and named users on the file afile?

Which command revokes ACL-based write access for groups and named users on the file afile?

• A. setfacl -x group:*:rx,user:*:rx afile
• B. setfacl -x mask::rx afile
• C. setfacl -m mask::rx afile
• D. setfacl -m group:*:rx,user:*:rx afile

Answer: (C)

The correct choice involves the use of the `setfacl -m` command with an activation of the mask. In this context, the mask plays a critical role in controlling the maximum permissions that can be granted to users and groups defined in Access Control Lists (ACLs). By specifying `mask::rx`, the command is setting the effective permissions of the mask, which subsequently restricts all named users and groups to read and execute (rx) permissions only. This effectively revokes write access because the write permission is not included in the mask. Setting the mask in this manner ensures that neither groups nor individual users can have write access if the mask does not include it, thereby enforcing a tighter security posture on the file. Utilizing the mask is an efficient approach to managing permissions collectively without the need to modify each entry in the ACL individually, which is practical in a situation where multiple users and groups may need their permissions adjusted consistently.

The correct choice involves the use of the setfacl -m command with an activation of the mask. In this context, the mask plays a critical role in controlling the maximum permissions that can be granted to users and groups defined in Access Control Lists (ACLs).

By specifying mask::rx, the command is setting the effective permissions of the mask, which subsequently restricts all named users and groups to read and execute (rx) permissions only. This effectively revokes write access because the write permission is not included in the mask. Setting the mask in this manner ensures that neither groups nor individual users can have write access if the mask does not include it, thereby enforcing a tighter security posture on the file.

Utilizing the mask is an efficient approach to managing permissions collectively without the need to modify each entry in the ACL individually, which is practical in a situation where multiple users and groups may need their permissions adjusted consistently.