Once I was strating the sshd service, I saw the error: Could not load host key: /etc/ssh/ssh_host_rsa_key issue.
Sometimes while starting the sshd service you may face some issues like the following:
Could not load host key: /etc/ssh/ssh_host_key
Could not load host key: /etc/ssh/ssh_host_rsa_key
Could not load host key: /etc/ssh/ssh_host_dsa_key
Could not load host key: /etc/ssh/ssh_host_ecdsa_key
Disabling protocol version 2. Could not load host key
sshd: no hostkeys available -- exiting.
Usually, these ssh security keys should have been created during the ssh installation itself. But unfortunately, if it is not mentioned to create these files automatically in the sshd configuration file, then you will definitely miss the keys and without these host keys the sshd service will not start.
Well, in such case either you set the corresponding sshd configuration file and restart the sshd service or restart your Linux or FreeBSD system so that these host keys can be generated manually.
Personally, I would suggest you to create these keys manually because finding the sshd configuration file is another overhead task because different systems have their sshd configuration files at different places.
How to create sshd keys to solve Could not load host key: /etc/ssh/ssh_host_rsa_key issue?
If ssh commands are already installed in your system then you can just execute the below command to create the keys manually:
ssh-keygen -b 1024 -t rsa -f /etc/ssh/ssh_host_key
ssh-keygen -b 1024 -t rsa -f /etc/ssh/ssh_host_rsa_key
ssh-keygen -b 1024 -t dsa -f /etc/ssh/ssh_host_dsa_key
ssh-keygen -b 1024 -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key
The first command will automatically generate all the required keys. But the second command will be helpful if you want to create only one of those keys and not all.
But I really do not see any difference of using the second step because the ssh-keygen -A will take care of creating the ssh keys for which there is no key has been generated yet.
In the second command the -b 1024 option specifies the key will be of 1024 bit length, and the -t option specifies the type of key: either rsa, dsa or ecdsa.
Sometimes the ssh is not at all installed on your system or you missed out to enable the ssh package while installing the OS. How you will come to know if ssh is installed or not?? just type ssh in your command prompt and to surprise you will see that command is not found or similar text.
Well, in such case you just see how to install a package in your system.
sudo apt-get install openssh-server should work in Ubuntu Linux
pkg install ssh or
pkg install openssh should work In FreeBSD.
Well I think this will mostly help you out to solve Could not load host key: /etc/ssh/ssh_host_rsa_key issue. If not then comment in the comment box and I will surely help you out.