Re: Server inaccessible after upgrade from 7.5 to 7.6

On 10/10/24 14:14, Sebastien Marie wrote:
> Mark <markbsdmail2023@gmail.com> writes:
>
>> Hi.
>>
>> I got 2 VPS, yesterday I upgraded one, from OpenBSD 7.5 to OpenBSD 7.6
>> (amd64),
>> today I wanted to upgrade the remaining one, after "sysupgrade -nk" and
>> "reboot",
>>
>> I cannot login to the system anymore (I manage only via SSH), Putty says:
>> "Remote side unexpectedly closed network connection",
>> after entering the password of my root user. I tried ssh in the Windows
>> terminal, same thing happens.
>>
>> ssh server is running, login: prompt arrives. And I see that my ssh client
>> disconnects after issuing the correct password.
>>
>> If the password is wrong, it attempts to ask for it again.
>>
>> I got no physical or console access to the server.
>>
>> Any idea would be much appreciated.
>
>>From your description, I assume your shell is from ports (bash, zsh,
> ...), and that after the upgrade of base, the binary of the port (from
> 7.5) doesn't run on 7.6 system for some reason. So, sshd runs (it is
> 7.6), you connect : sshd execve the shell, and it doesn't ends well.

that was my first assumption, too.

> You can try to connect to another user (if possible) using some base
> shell, or try to get a console (the getty) and logs as root (assuming
> the shell of root is still ksh).

Might try this:
ssh remotehost ksh

it will probably look like it hung, but it might not be -- you are just
sitting at ksh without $PS1 (or much of anything else) set. You might
be able to gain control of the system sufficiently to run pkg_add -u.

Here's an actual demo:
$ uname -a
OpenBSD fluffy3.in.nickh.org 7.5 GENERIC.MP#171 amd64
$ ssh dbu1 ksh
uname -a # note lack of prompt, motd, or anything...
OpenBSD dbu1.in.nickh.org 7.6 GENERIC.MP#337 amd64
# but I'm in!

you can get around some of the no prompt/no motd stuff by
doing "ssh <host> ksh -li", but it's still quite weird.

you know all those times when you said, "I don't need to know
'ed(1)'"? well...maybe you now need it.

Warning: when I promoted myself to root, the PW echoed on the screen.
So...beware of shoulder surfers. :)
(and I'm sure there are fixes for all these issues, but I didn't hunt
very hard)

Nick.