When the ntpdate package is installed, one gets at boot something like:

Debian GNU/Hurd stretch/sid debian console
task ext2fs increasing a bogus port 947 by 1, most probably a bug.
task ext2fs increasing a bogus port 947 by 1, most probably a bug.
task ext2fs deallocating a bogus port 947, most probably a bug.
task ext2fs deallocating a bogus port 947, most probably a bug.
login:

This is coming from the execution of the shell script /etc/network/if-up.d/ntpdate, whose stdout/stderr is on the Mach console, but part of which gets executed after getty starts on it. It happens that getty uses revoke() to revoke access to it from other programs, and thus the ntpdate shell scripts gets its stdout/stderr in a bogus state, which libc doesn't really cope with correctly.

Commenting c:23:respawn:/sbin/getty 38400 console from /etc/inittab works around the issue (but removes the getty from the Mach console)