How do you change the default permissions for files?

Question

I have all my users saving (via AFP) to an Xserve RAID, I am using ACL to control who has access to certain area.
This is fine when moving files in the finder, all ACL are respected, however when saving files from Photoshop it ignores the ACL's.
So if user A saves a file they become the owner- which is fine, but the group and everyone permissions are read only, so when user B ammends the file they get a permission warning when they try to save, the work round I'm using is to trash the file just before you try to save- not ideal cos if the save fails you've lost the work.
What I would like is for the default permission to be group "design" Read and Write and leave everyone as read only
So when any designer goes to oversave a file in photoshop they can do.
I needf to leave ACL's on as they are working well in every other situation, i.e I have certain folders set so once images have been added they cannot be deleted or renamed by certain users.
It only seems to be Photoshop that gives us this problem, Quark files and other docs are able to be saved according to the ACL

Answer 1

Hi
There are some important distinctions and points to be made here.
POSIX Permissions are always set for every file and folder. ACLs are optional for any file, folder or share point and work IN ADDITION to POSIX Permissions. SACLs (Service Access Control Lists) are optional for specific services such as AFP, FTP, SMB, Mail etc and are independent of files and folder as well of standard POSIX Permissions and file system ACLs. Allow access is cumulative and Deny access is first match.
ACLs supersede but don’t necessarily override Standard UNIX permissions.
The best way to use ACLs is to enable Access Control Lists on the desired volume, create the share point folder from within Workgroup Manager, define the Users and Groups and then drop the relevant User and/or Group into the ACL window and define access privileges from there. Don’t be tempted to use the Standard UNIX permissions in addition to ACLs as all sorts of problems can ensue.
Privileges and access can quickly get confused and share points can be broken. Deny settings defined in ACL take precedence over all other privileges settings. Deny settings defined using Standard UNIX as well as ACLs can, in some cases, mean share points becoming inaccessible to all users even those with administrative privileges.
Wherever possible try not to set access privileges using the Finder.
For a much fuller explanation and a method for calculating umask values consult Gerrit de Witt’s series of articles:
http://discussions.apple.com/thread.jspa?messageID=648307&#648307