I've not tested this. I'm making a guess. I built a SoYou server using a ssh key on the install. Thus no root password issued and crucially, nor did I remember to set one and make a note of it. My fault. All was fine... on a routine update, I lost ssh access. This was Monday. The server is a backup node so actually, I just rebuilt it. While figuring out the how something else I wondered on how it happened, I think I sussed it. The centmin sshd_config template seems to have authorized_keys specified. The new build on soyou (cent7) creates an authorized_keys2 file. QED on the restart of sshd, the authorized_keys2 isn't going to be checked. I don't tend to change my ports, instead I add CSF to block everything except via ssh bastions/jumps, hence I didn't change the sshd config initally. It might be something else, I'm making 2+1 equal 4 here. I didn't have the root pw so the box was as good as dead. I didn't have the time to ask soyou to reset the root, if it's something they can even do. Feel free to delete if the above is just a distraction/non issue.