Question: After some automatic updates (or being hacked?) I have many things broken and a huge problem to resolve them since **I can't login as root anymore**.

* ssh admin: login success
* su root: permission denied (probably not the same password)

What I have tried:

* read log: but permission denied
* use 'synopass' and empty password: failed
* use synouser: permission denied
* change password of admin hoping it will update the root password: failed.
* check the root user in /etc/passwd: he is ok (with ash)
* restart all the server: failed

I have no idea what is going on. Any advice?

Answer: 
In DSM Version 6 you can still login as root when using RSA keys. Therefore just copy your public key as admin to your Synolgy:

```
$ cat ~/.ssh/id_rsa.pub | ssh admin@192.168.1.10 'umask 077; cat >>/tmp/authorized_keys'

```

After that login to your Synology as admin and become root:

```
$ ssh admin@192.168.1.10
admin@192.168.1.10's password:
admin@My-Synology:/$ sudo -i
Password: 

```

No create the .ssh directory for root, move your key and change the owner of that file:

```
root@My-Synology:~# mkdir -m0700 /root/.ssh
root@My-Synology:~# mv /tmp/authorized_keys /root/.ssh/
root@My-Synology:~# chown root:root /root/.ssh/authorized_keys

```

After that you can login to your Synology as root without having to enter the password.
You can also just SSH using rsa keys, then you can SSH as root, even after installing DSM6, without making any additional changes.