setfacl

However, setfacl doesn’t modify the actual file ownership like chown does. It works on file permissions for users/groups. If you need to change the actual ownership (user and group), chown is still required. ACLs can be useful to manage additional permissions, but they don’t change the file’s owner directly.

replicate ACl form one folder to another

Copy ACL from another directory

To copy the ACL (Access Control List) from one file and set it to another file using setfacl and getfacl, you can follow these steps:

1. Get the ACL of the source file: Use getfacl to extract the ACL of the source file. This command retrieves the ACL and outputs it in a format that can be applied to another file.

   getfacl source_file > acl.txt

   This saves the ACL of source_file to a file named acl.txt.

2. Set the ACL to the destination file: Use setfacl to apply the ACL stored in acl.txt to the destination file. The --set-file option is used to set ACLs from a file.

   setfacl --set-file=acl.txt destination_file

   This will set the ACL of destination_file to be the same as the ACL of source_file.

Mask

In setfacl, the mask plays an important role in determining the effective permissions for group users and named users or groups. The mask acts as a filter that limits the maximum permissions these users or groups can have.

Here’s a quick guide on how to use the mask in setfacl:

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Key Points

1. Mask Role:

   • The mask applies only to the permissions of group owners, named groups, and named users.
   • It does not affect the owner or “other” permissions.

2. Setting the Mask: Use the -m option with setfacl to modify the mask.

Examples

1. Set a Mask

To set a mask that limits maximum permissions:

setfacl -m m:rwx <file_or_directory>

• m specifies the mask.
• In this example, the mask allows read, write, and execute permissions.

2. View the Mask

To view the current ACLs, including the mask:

getfacl <file_or_directory>

The output will show the mask:

# file: example.txt
# owner: user1
# group: group1
user::rw-
group::r--
mask::rwx
other::r--

In this example, even though the group has r--, they can potentially get rwx because of the mask.

3. Test Mask Effect

Suppose you give the group full permissions:

setfacl -m g::rwx <file_or_directory>

Then reduce the mask:

setfacl -m m:rx <file_or_directory>

Now the group will only effectively have rx permissions, even though they were originally granted rwx.

4. Remove the Mask

To remove all ACLs (including the mask):

setfacl -b <file_or_directory>

This resets permissions to the standard Unix file permissions.

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Use Cases

• Restrict Group Permissions: Use the mask to limit excessive permissions accidentally granted.
• Audit and Manage: Ensure controlled access by applying masks to sensitive files.

Let me know if you’d like more examples!