dokku: Does ssh work only if public key is stored in id_rsa.pub?

Question

My environment: Ubuntu server v. 18.04. with Dokku v. 0.20.3. Server IP is 192.168.xy

The Problem: From a local system I run command

git push dokku master

Now I am asked for a password:

dokku@192.168.x.y's password:

The Question: I added a new ssh key and gave it a new name id_rsa_dokku.pub. When adding the new ssh from id_rsa_dokku.pub to dokku server. It never works. Only if I copy the old key from id_rsa.pub. It would work then. Why? Does ssh works only from the id_rsa.pub?

Answer 1

Could finally add the key using this command on the server:

echo <public_key> | sudo dokku ssh-keys:add dokku