Two days ago I upgraded shells/zsh to version 5.5 on my FreeBSD 11.1-RELEASE-p9 (amd64) machine. During a login over serial line (wired or IPMI-SOL) I am immediately kicked out after a successful login. Syslogd shows: <kern.info> xxx kernel: pid xxx (zsh), uid 0: exited on signal 8 (core dumped) I immediately downgraded to zsh-5.4.2_1 and the error disappeared.
5.5 release commit: https://github.com/zsh-users/zsh/commit/f9e9dce5443f323b340303596406f9d3ce11d23a 5.5.1 release commit: https://github.com/zsh-users/zsh/commit/fd4056f4edb12000ac5b0181aef8bb741e60801c You can dig through the delta commits to see what changed, but this is almost certainly the commit that fixes the problem: https://github.com/zsh-users/zsh/commit/68d9526220d77466a75928fc6a20008cf64e0590 In my experience, on serial console (thus also IPMI serial), terminal size is 0x0. I believe stty -a used to show this, as I remember having to manually run 'stty rows Y columns X' manually when on serial console. There may be tput/etc. stuff that can figure this out, but doing that automatically is not always reliable/dangerous (i.e. shouldn't be in dotfiles by default, especially considering that it shouldn't be run for non-interactive sessions). Not all serial consoles/multiplexers are the same. HTH, and provides a most-likely root cause commit. P.S. -- I do not use zsh, I just know a lot about serial terminals. :)
(In reply to Jeremy Chadwick from comment #1) Thank you very much for your detailed analysis. In a parallel way I have been told by Baptiste via the mailing list that he could not reproduce (anymore) the error with version 5.5.1. He asked me to test myself. Meanwhile, I could have tested version 5.5.1 and can confirm that the error has been fixed.