genoso - the SSH copy recursive command might not be of muchhelp to the OP if they aren’t familiar with Unix.
The reason you aren’t able to su to another user is because the SSH sessions are locked down on EX2/EX4 to just the sshd user. If you look at /etc/ssh/sshd_config, you will see that the only allowed SSH user is sshd. There is a way to hack that, but it’s not easy (involves modding a couple files in firmware code that is available for download and then re-building the firmware and very likely voids your warranty though if you know how to do it and what to do it is perfectly safe…and reversible should you want to go back to the official firmware and lose this ability to add additional user logins in SSH sessions). Without this hack, if you just edited the file and rebooted EX2 to take effect, the changes will to sshd_config will be lost because a fresh file will be copied over. I gave an outline of this hack (primarily to enable SFTP on EX2 for my friends who are non root users) in this thread → http://community.wd.com/t5/WD-My-Cloud-EX2/SFTP-possible-on-EX2/td-p/715812
I’m not fully sure why you’d want to su anyway for the copy process though. If it is to preserve permissions of file then remember, you can use the copy command’s -p switch (so copy -rp) to copy recursively while retaining permissions.
