Allow SSH root login on Ubuntu 20.04 Focal Fossa Linux

Open the /etc/ssh/sshd_config file with administrative privileges and change the following line:

FROM:
#PermitRootLogin prohibit-password
TO:
PermitRootLogin yes

The quick way to do this job could be just to simply use the sed command as shown below:

sudo sed -i 's/#PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config

Restart SSH service:

$ sudo systemctl restart ssh

By default the root’s password is not set on Ubuntu 20.04 and the error message Permission denied, please try again will appear when attempting to SSH login as a root user. From this reason we need to set root’s password. When prompted enter your current user password followed by new root password:

$ sudo passwd
[sudo] password for linuxconfig:
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Given that your Ubuntu 20.04 system allows incoming traffic on port 22/ssh, you should now be ready to SSH login as root:

$ ssh root@ubuntu-server
root@ubuntu-server's password:
Welcome to Ubuntu Focal Fossa (GNU/Linux 5.3.0-23-generic x86_64)