re-generating ssh host keys

[Michael O'brien_1]

Hi,

I've recently cloned a box using ignite. I would now like to regenerate the host keys in /etc/opt/ssh/ssh_host*

Can anybody tell me how to re-generate the host keys

Thanks
Michael

[Sundar_7]

ssh-keygen -t dsa

Will do.

[Michael O'brien_1]

Hi Sundar,

I need to re-generate the host keys rather than user keys. When I run the ssh-keygen -t dsa, this will promote me to create the ./ssh/id_dsa rather than /etc/opt/ssh/ssh_host_key

Thanks
Michael

[Sameer_Nirmal]

Remove the existing host/pub (rsa/dsa) keys.
Generate ssh host keys using as per your requirements.

# ssh-keygen -t (rsa/dsa) -f /etc/opt/ssh/ssh_host_{rsa/dsa}_key -N ''

[Sameer_Nirmal]

Note there is a space between the two quotation marks afer -N

This is because host key generation requires a null new passphrase.

[Michael O'brien_1]

Hi Sameer,

Thanks for the reply, I'm okay with generating the ssh_host_rsa_key and ssh_host_dsa_key. In the /etc/opt/ssh directory it has 3 sets of keys

ssh_host_rsa_key
ssh_host_dsa_key
ssh_host_key

How do you generate the ssh_host_key

Thanks
Michael

[Sundar_7]

Michael,

ssh-keygen can be used to create both user's and hosts' SSH keys.

You can specific the file name /etc/opt/ssh/ssh_host* in the prompt.

That will create the SSH key for the host.

Sundar.

[Sundar_7 · Accepted solution]

Michael,

By default only /opt/ssh/etc/ssh_host_dsa_key is used.

Verify your SSH server configuration.

# grep "HostKey" /etc/opt/ssh/sshd_config

Sundar.

[Sameer_Nirmal]

Using following command, you can create the key.

# ssh-keygen -f /etc/opt/ssh/ssh_host_key -N ''

[Steven E. Protter]

Shalom Michael,

ssh-keygen -t rsa

Generates a smaller key file.

SEP

[Heironimus]

ssh_host_key is the ssh1 RSA key. You can create those with "ssh-keygen -t rsa1".