Server

• install ssh-krb5
• Add "forwardable" to the pam_krb5 line in common-auth
• Add a host principle and add it to that host's keytab
• Restart ssh-krb5

Client

• install krb5-user
• Add the lines below to ssh_config
• kinit

# Add the following to /etc/ssh/ssh_config:
GSSAPIAuthentication yes
GSSAPIDelegateCredentials yes