Upgrade results in SSH access error

[castor]

Hello, I have a trouble of connecting to server via SSH:

$ ssh -v remote.host
OpenSSH_5.9p1-hpn13v11, OpenSSL 1.0.1e 11 Feb 2013
debug1: Reading configuration data /home/castor/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to remote.host [some.ip] port 22.
debug1: Connection established.
debug1: identity file /home/castor/.ssh/id_rsa type 1
debug1: identity file /home/castor/.ssh/id_rsa-cert type -1
debug1: identity file /home/castor/.ssh/id_dsa type -1
debug1: identity file /home/castor/.ssh/id_dsa-cert type -1
debug1: identity file /home/castor/.ssh/id_ecdsa type -1
debug1: identity file /home/castor/.ssh/id_ecdsa-cert type -1
ssh_exchange_identification: Connection closed by remote host

This have happened today at night when I was doing upgrade of 8.0-RELEASE to 8.4-RELEASE remotely via SSH. Process was in tmux session, so after starting first freesbd-update install I disconnected but then have no ability to connect back. Server refuses connection with error described above.

What will happen if local user reset the server? Will server work correctly after reset or will this trouble keep on?

 

[castor]

And the answer is NO. freebsd-update install was terminated by unknown reason and sshd was unable to start in half-upgraded system after reboot.

 

[junovitch@]

The first freebsd-update install is only the kernel update. No userland components were changed. That shouldn't have had an impact on SSH. Have you been able to get back in and complete the update?

 

[castor]

The first freebsd-update install is only the kernel update. No userland components were changed. That shouldn't have had an impact on SSH. Have you been able to get back in and complete the update?

Yes, I finished update with help of local user.
After reboot SSHD was not able to start because of error (user took photo and send it to me)

/libexec/ld-elf.so.1: Undefined symbol "output" refereenced from COPY relocation in /usr/sbin/sshd

So I supposed that update was interrupted incorrectly. But after running freebsd-update install once more FreeBSD was cured.