Generating the Server Host Key Pair

The host public-key pair (1536-bit RSA) is generated during the setup of Tectia Server. You only need to regenerate it if you want to change your host key pair.

Tectia Server for IBM z/OS includes a program that generates a key pair, ssh-keygen-g3, which is located in /opt/tectia/bin.

Generate the key pair for the server in such a way that the private key has no passphrase (option -P). The server will then start up without any operator interaction to enter a passphrase. Protect the key with file system access rules. The private key (/opt/tectia/etc/hostkey) must be accessible only by the SSHD2 user.

To (re)generate the host key, perform the following tasks:

Use su to switch to a UID 0 user (if you are not already logged in as one).
Run ssh-keygen-g3 to generate the host key, for example:
```
# /opt/tectia/bin/ssh-keygen-g3 -t rsa -P /opt/tectia/etc/hostkey
```
This will generate a 2048-bit RSA key pair without a passphrase and store it under /opt/tectia/etc.
For more information on the key generation options, see the Tectia Server for IBM z/OS User Manual or the ssh-keygen-g3 man page.
Restart the server as instructed in Restarting the Server.