Red Hat Bugzilla – Bug 42280
Serial console and single user mode don't cooperate
Last modified: 2007-04-18 12:33:25 EDT
I am booting with a serial console (here is the line from aboot.conf:
0:1/vmlinuz root=/dev/sda3 console=ttyS0
If I try to shutdown to single user mode ("shutdown now"), I get the shell
prompt, but it doesn't take input from the serial console.
If I try to boot up in single user mode (by specifying "single" or
"emergency" on the boot command line), the same thing happens. All the
output appears okay (up to the point of a password or shell prompt), but
input doesn't work. It just sits there (my characters are not echoed back).
Is input accepted from a local terminal, or just not at all from anywhere?
I'm not sure I understand your question. When I shutdown to single user mode
with a serial console, the only place input should be accepted from is the console.
I have a null modem between my desktop computer (x86 7.1 running minicom) and
the Alpha that is having this problem. When the Alpha is booted up, I can log
in via the serial port just fine (I added an agetty line for ttyS0 to
/etc/inittab and ttyS0 to /etc/securetty). If I then log in as root everything
works until I try to run "shutdown now". The Alpha goes through the normal
shutdown process and then starts the single user mode shell. I get the prompt
on the terminal, but I cannot enter anything (my input is ignored).
I just tried this on an x86 Red Hat 7.1 system here, and it works just fine, so
this is somehow specific to the Alpha.
What I meant was that, in the case where you have output to the serial console
but no input, if you plug in a keyboard, does that work? (It shouldn't, but
it would be good to know if it does...)
Ah, I understand, sorry.
No, that does not work either. However, the reboot keystroke (I change it from
CTRL-ALT-DEL to CTRL-ALT-BS) _does_ work. Interesting.
I'm changing this to SysVinit instead of initscripts, since I now realize that
the init program itself is in charge of this, not the init scripts.
Can you try it on a Red Hat x86 system, *with the same kernel version* that's
on the alpha?
I just compiled the 2.4.3-7 kernel on my x86 system, and the same thing _does_
happen (single user mode with serial console is broken). I see that both
drivers/char/console.c and drivers/char/serial.c had changes.
OK, I reproduced it on ia64 with 2.4.3-7 as well.
Bill, dump the stty -a settings of that port at the point it starts the shell. I
suspect your terminal settings are wrong
speed 115200 baud; line = 0;
kill = ^X;
-brkint ixany -imaxbel
-iexten -echoe -echok echoprt
(This is in /etc/init.d/single. I *think* this is pointed at /dev/console
(aka, the serial port) at the time.)
*** This bug has been marked as a duplicate of 45284 ***