容器之间ssh设置免密登录，容器是Ubuntu系统，docker是桌面版，请问这是什么问题

Question

root@pbs1:/# ssh-copy-id root@pbs2
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host 'pbs2 (172.18.0.4)' can't be established.
ECDSA key fingerprint is SHA256:o9SNSaGPMMGoCGUmBqiGy4BWnJnh1Yzt8x0fIey5bZA.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@pbs2's password:
Permission denied, please try again.