debug shell unusable due to continuous systemd output

[mbiebl]

Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=770755

Using the debug shell on tty9 is seriously hampered by systemd output, say when you get the eye of cylon output for units which fail/take long to start.
It becomes basically impossible to use the shell on tty9 in such a case.

[poettering]

Well, what are you proposing we do about this?

[mbiebl]

continue to output to the tty which was active during boot?

[poettering]

we output status info to /dev/console, and nothing else really. I am pretty sure we shouldn't access any other tty for that.

[mbiebl]

can we supress output if tty9 is the active console?

[dimyme]

there are e.g. 2 workarounds:

• patch out the cylon with an immediate " return; " statement near

  systemd/src/core/manager.c

  Line 187 in fb4b046

  static void manager_print_jobs_in_progress(Manager *m) {

• use a kernel boot-parameter like: linux /boot/vmlinuz root=UUID=3… console=tty3 # in /boot/grub/grub.cfg

the latter will keep the Ctrl-Alt-F9 debug-shell and others tidy from the dreaded Cylon in case of the popular "A stop job is running on…"

[dimyme]

we shouldn't access any other tty for that.

That above kernel boot-parameter can take care of it handily.

[keszybz]

I haven't seen this issue in a long time. Maybe this is fixed already.