Summary
We recently encountered with ‘sshd error: could not load host key’. The fixing is quite easy in Ubuntu Linux system yet you should be careful while solving the issue.
This time we found this problem in Ubuntu 18.04 LTS Server Edition whereas the method is applicable to other Ubuntu and Debian based Linux Operating System also.
Sep 29 16:01:28 lab sshd[1088]: error: key_load_private: invalid format Sep 29 16:01:28 lab sshd[1088]: error: key_load_public: invalid format Sep 29 16:01:28 lab sshd[1088]: error: Could not load host key: /etc/ssh/ssh_host_rsa_key Sep 29 16:01:28 lab sshd[1088]: error: key_load_private: invalid format Sep 29 16:01:28 lab sshd[1088]: error: key_load_public: invalid format Sep 29 16:01:28 lab sshd[1088]: error: Could not load host key: /etc/ssh/ssh_host_ecdsa_key Sep 29 16:01:28 lab sshd[1088]: error: key_load_private: invalid format Sep 29 16:01:28 lab sshd[1088]: error: key_load_public: invalid format Sep 29 16:01:28 lab sshd[1088]: error: Could not load host key: /etc/ssh/ssh_host_ed25519_key Sep 29 16:01:28 lab sshd[1088]: fatal: No supported key exchange algorithms [preauth]
How to fix “sshd error: could not load host key”
Follow the given below steps to solve the issue.
Take Backup of sshd directory
First take the backup of ssh config folder. In case of any blunder, you can restore the file to previous state.
sudo cp -rvf /etc/sshd ~/sshd-backup
Remove ssh host key
Remove the ssh keys file inside /etc/ssh directory.
sudo rm /etc/ssh/ssh*key
Regenerate ssh key
In this step, now recreate the new ssh key files.
sudo dpkg-reconfigure openssh-server
Restart the openssh-server
As we have done the changes in ssh, restart the ssh service by using given below command.
sudo systemctl restart ssh
Now try connecting by using ssh command to server/system. We hope it will be working!
