[Server-devel] [XSCE] CentOS 7 quirk: VGA cable not re-attachable

[Adam Holt]

On Mon, Aug 29, 2016 at 5:21 PM, Alex Perez <aperez at alexperez.com> wrote:

>
> > On Aug 29, 2016, at 2:16 PM, Adam Holt <holt at laptop.org> wrote:
> >
> > Might anyone know why the VGA (or Mini DisplayPort) cable can never be
> unplugged from CentOS 7.2 (even for a second, forcing you to somehow
> reboot[*] if you want to restore video) but yet this ain't a problem on
> Fedora 22 and similar -- as I've demonstrated with several units of the
> same very NUC6i3SYH hardware, and also on 4th gen NUC D34010WYKH ?
>
> I can think of a number of reasons why this might be happening. Just to
> confirm:
>
> 1) This doesn’t happen with Fedora 22, on the exact same NUC (not a
> different one, even if it’s the exact same model)?
>

Confirmed: Fedora 22 does not have this problem, on the exact same NUC.
I've swapped hard drives between NUC's to reconfirm (in fact) the problem
results from each hard drives that contains CentOS 7, and not the other(s)
containing F22 -- regardless which physical NUC PC I insert the drives into.


> 2) It could just be a bad/flaky NUC.


No, see above :)

Does this model of NUC have a physical VGA port, or are you using some sort
> of adapter cable?
>

I'm using a Mini DisplayPort-to-VGA adapter cable, as the NUC6i3SYH
and D34010WYKH
do not take VGA cables directly.  The same adapter has been used in all
tests, across all 3 NUC's, regardless which drive was inserted.


> 3) It could be the monitor/LCD’s sync circuitry being insolent. Are you
> using the same monitor in both the case that works reliably, and the case
> that doesn’t?
>

All tests (across all 3 NUC's) were done using the same 17-inch LCD monitor.

I suppose I could try installing F19 if it was important to
assess/ascertain that CentOS 7 is inheriting this problem from a flaky
version of Fedora -- but of course I'm far more interested in a possible
fix (if such exists, as CentOS 7 will be around for many more years) rather
than playing archeologist with Fedora 18/19/20 :)


> > I do understand that CentOS 7.2 is largely based on Fedora 19 from July
> 2013, whereas Fedora 22 was released almost 2 years later May 2015 -- but
> the ability to attach/reconnect any VGA monitor at any time is something
> most PC's could handle over recent decades (even after boot, or if the VGA
> cable falls off for a second, etc).
> >
> > Might there be a way to make the VGA (or Mini DisplayPort) cable less
> fragile within CentOS 7 on Intel NUC's, or some setting within CentOS 7
> that might have gone wrong?  Aside: I used Jerry Vonau's pre-XSCE-6.1 ISO
> from July to install CentOS 7.2 in this case.  No worries if conversely
> this is a CentOS 7 bug/quirk we just have to live with; still as a major
> annoyance during in-person debugging/support, I thought I'd ask!
> >
> > [*] or worse, earlier today one CentOS7 NUC did not bring up video 4
> reboots in a row -- it was only by ssh'ing in remotely to this NUC that I
> was able to restore video/monitor output, after typing "reboot" at the
> prompt (something that a rural/impoverished deployment would never do,
> realistically!)  In most cases, a couple forced poweroffs do the job of
> restoring video output (touching the NUC's power button turns it off within
> 2 seconds generally -- if the NUC does not produce video output on the next
> boot, then FYI the 2nd boot (almost) always works.
>
> --
> Unsung Heroes of OLPC, interviewed live @ http://unleashkids.org !
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.laptop.org/pipermail/server-devel/attachments/20160829/af08c9f6/attachment.html>