What must be done to allow only users of the devel system group to access a share?

In Samba's `smb.conf`, the `valid users` parameter is used to specify which users or groups are permitted to access a share. When a group name is prefixed with an `@` symbol (e.g., `@devel`), Samba interprets this as a UNIX group, thus granting access to all authenticated members of that specific system group.

While `valid groups` exists, `valid users = @groupname` is the more direct and common way to restrict initial share access to members of a specific Unix group.

Setting `valid groups = devel` without the `@` symbol would mean Samba looks for a *user* named 'devel' or might not correctly interpret it as a Unix group, failing to achieve the desired group-based restriction.

Changing Unix filesystem permissions via `chgrp` and setting the GID bit controls underlying file access but does not directly govern who can connect to the Samba share itself; Samba's `smb.conf` parameters manage share-level access control.