[systemd-devel] PATCH: fix logind on xen

[Jan Engelhardt]

On Friday 2012-01-06 18:37, Lennart Poettering wrote:
>>> 
>>>"console" logins? What exactly is that? Logins on /dev/console?

In /etc/inittab:
	cons:12345:respawn:/sbin/smart_agetty -L 38400 console

(Solaris 8 did something similar, as it does not have a tty multiplex on
console like Linux by default.)

The reason to use this - with sysvinit-based systems - is that,
if I would specify

	hvc:12345:respawn:/sbin/smart_agetty -L 38400 hvc0

instead, spawning the getty on hvc0 could repeatedly fail if the particular
xen guest image used xencons=tty instead of xencons=hvc0.

In case of systemd, that is all a no-brainer, because systemd spawns
gettys on the console= device automatically and one does not have to
think about it.

>>>Where
>>>does /dev/console point to? i.e. what is the contents of
>>>/sys/class/tty/console/active if you do that?
>> 
>> Sorry, I was unclear. On Xen, you can login on a "text" terminal. When
>> doing that, /sys/class/tty/console/active outputs : tty-1 tty0
>
>Hmm? So it claims "tty0" in that file, bug actually no /dev/tty0 device
>exists? That souinds like a kernel bug to me.

1. xencons=hvc (the modern variant)
   creates: /dev/hvc0
   implied defaults: console=hvc0
   <sysfs>/active: "tty0 hvc0"
   /dev/tty0..63 exist.

2. xencons=xvc
   creates: /dev/xvc0
   implied defaults: console=tty0 (!)
   <sysfs>/active: "xvc-1 tty0" (bug?)
   /dev/tty0..63 exist.

3. xencons=tty
   creates: nothing new
   implied defaults: console=tty1
   <sysfs>/active: "tty-1 tty0" (bug)
   /dev/tty1..63 exist (!), no tty0.

4. xencons=ttyS
   creates: /dev/ttyS0
   implied defaults: console=tty0
   <sysfs>/active: "ttyS-1 tty0" (bug...)
   /dev/tty0..63 exist.

What a mess...