I have set up an environment for file sharing with Linux as server and Samba as a PDC for winXP Client Workstations on it. I have shared a folder called CT for edt group to access and store and write or modify files in that. Earlier the same folder was in Windows 2K3 server and I copied all files to linux samba share (CT) and change the group to edt using the command chgrp, also changed the permission to write and read for both owner and group. All are going fine except the problem of permission, whenever the group member add files or folders under the folder CT, the folder can only be writable for owner and groups and others are only having read access. Everytime after adding a file or folder by the edt group member, I have to change the permission to 770 manually. In a live environment I'm not able to proceed with kind of follow ups, I want to set 770 as permission for CT folder permanently.

Try setting the following 2 parameters under your share definition:

[CT]
create mode = 0660
directory mode = 0770

That will make all folders created by users have rwxrwx--- and files will have rw-rw----

Owner and group will be user and user's pirmary group. If you are running version 3 of samba, you can also use the "net groupmap" command to map standard windows groups to your Linux groups, which can cause errors when changing permissions on files on the shares from a Windows box.