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Re: Spurious character typed on console every ~20 secs until logged in




On Thu 29 Mar 2018 at 17:20:58 (+0200), tomas@xxxxxxxxxx wrote:
> On Thu, Mar 29, 2018 at 10:10:55AM -0500, David Wright wrote:
> > On Thu 29 Mar 2018 at 10:46:17 (+0200), tomas@xxxxxxxxxx wrote:
> > > On Thu, Mar 29, 2018 at 08:24:03AM +0000, Curt wrote:
> > > 
> > > [...]
> > 
> > Thanks for the ideas. I hadn't come across the virtual buttons.
> > 
> > I think I'll look at what processes are running by the time it
> > tries to mount /home, and which of them might involve looping on
> > that timescale.
> 
> If it's something in user space, it'd be interesting who has
> the console open.

That comment made me remember about one possible candidate; I have
@reboot /sbin/kbdrate -r 8 -d 500 -s
in root's crontab as a matter of habit. But removing it had no effect.

I can definitely only observe two CRs, one at the unlocking prompt
(assuming I wait for it), and one at login. Of course, to be able
to observe a third, I have either start typing my username or press
<return> (in order to get the cursor out of column 1) and that very
keystroke could be enough to stop whatever's happening.

> > Then, when it happens again, I'll try a remote login to see if
> > I can catch some process at it. It hasn't yet happened (on the
> > three occasions) at an opportune time for me to investigate.
> > 
> > I agree, the first character is probably a NUL. The second is
> > probably CR. Both can be used to terminate strings in different
> > situations. Or perhaps my termcap has fallen into a 1960s wormhole:
> > anyone remember WRU, and the Here Is key, …
> 
> Faintly. I also dimly remember about some serial interfaces
> sending NULLs when idle, but I can't put my finger on that.

My memory of these machines is of a roomful of them all bursting
into life when they rebooted the PDP11 in town, two miles away.
Then waiting for peace to be restored as their motors timed out.

> The advantage of old age is that you tend to forget things :)

Cheers,
David.