Fix permissions on files copied to samba shares automatically

so I have a samba share where I have multiple groups and user. in my case:

A user named CEO would be a member of groups Partners and Users,

While user Clerk would be just a member of group Users .

There are 2 Shared folders, Common, and Partners-only. Common would be owned by users and Partners-only by Partners. So the CEO can Access both Common and Partners-Only, while Clerk can only Access Common.

Now the issue is that when CEO copies something from Partners-Only onto Common, the permission stay that the file is owned by Partners group and any regular user cannot access the file.

I have a fix for it with crontab that goes like this:

*/5 * * * * /usr/bin/chgrp  -R Users /mnt/Common/ >> /var/log/permissions/Common.log 2>&1
*/5 * * * * /usr/bin/chmod  -R g+rw /mnt/Common >> /var/log/permissions/partners.log 2>&1

And it works, however, the issue is that with many different groups and shares I have simular cronjob too many times and it puts too much strain on the server.

Is there a way to get samba to adjust permissions on its own when a file is copied? thanks

How about something like this ... assuming I have a folder at /mnt/Common:

Change ownership and apply the setgid bit to that folder:

sudo chown :users /mnt/Common
sudo chmod 2775 /mnt/Common

The setgid bit will force every new file added on the server itself to this directory to inherit the group of the parent.

Then create a share definition in smb.conf that looks something like this:

[Common]
path = /mnt/Common
valid users = @users @partners
force group = users
writeable = yes
create mask = 0664
force directory mode = 2775

When a member of either group adds a file to the share it will save with group = users and permissions of 664. Any new subdirectory added will save with group = users, set folder permissions to 775, and will apply the setgid bit to that subdirectory.