Create a secondary SSH daemon for backdoor access during special management of server.

1) Start sshd backdoor:

/usr/sbin/sshd -p 22222

You will have two instances of sshd running now.

2) Login back in using the 22222 port backdoor:

ssh -p 22222 user@server.com

3) Find the old running sshd and kill it:

ps auxww | grep ssh
kill -9 [pid]

4) Start the new daemon on standard port:

/usr/sbin/sshd -4

5) login in using the standard port 22. and kill the sshd on 22222:

ssh -p 22 remote@host.com
ps auxww | grep ssh
kill -9 [pid]