Synology DSM - Can't log as root (but works with admin)

If your synology is in DSM6 and you're logged with a user part of administrator group, you can do :

sudo -i

enter your root/admin password

or even sudo su - (it works to)

now you're root tadaaa

Your Synology probably upgraded to DSM6, in which security has been hardened... In DSM6 you can no longer use root for SSH, but you can use any other member account of the administrators group. Mind that you now need to sudo when logged in using SSH.

See the DSM6 release notes!

You can also just SSH using rsa keys, then you can SSH as root, even after installing DSM6, without making any additional changes.

If you're still with DSM Version 5, you might have logged in as admin instead of root. This makes a difference, even though root and admin share the same password.

To solve, do

ssh root@synology.local

with using the admin password.

This will log you in as root, with root access.