I would like to create a folder in my OPT directory on Ubuntu 14.04. However, it must have the following requirements:
nobody)test-user). Root shouldn't be able to write.
Can not be deleted by ANYONE, even root.
Nope. root can always remount the disk or (better) remove any restrictions you put into place.
ReadOnly access to ALL users (except nobody)
See 3.
Write access ONLY by my user (test-user). Root shouldn't be able to write.
Nope. root can always remove any restrictions you put into place. You can mount (example: //youserver/sharename /mnt/mountpoint cifs username=yourusername,password=yourpassword,file_mode=0664,dir_mode=0775) a partition for a user but not block root access.
root can always (and has to always be able to) change anything that can form any sort of restriction. Otherwise you can end up with an unusable system that can only be formatted to get it working again.
If you have a root user that you do not trust then change the password and force them of the system. Otherwise this is moot: you will have to trust your admin.
