ACL Mask Value in Linux: Explained with Examples (Access Control Lists Mask)

https://linuxdatahub.com/masks-in-acl-linux-explained-with-examples-access-control-lists-mask/
https://linuxdatahub.com/access-control-lists-acl-in-linux-explained/

https://www.liquidweb.com/kb/what-is-umask-and-how-to-use-it-effectively/

chmod 770 bbs
setfacl -m m::rwx bbs

Change ACL mask
ACL mask can be changed using 2 ways
Using chmod and setting permission to group : When permission of the group for a file or directory is changed, it directly changes the mask .

Using setfacl : mask can be overridden by setfacl command setfacl -m m::<perm> <file/dire>.
For example: