[mythtv-users] Slightly OT: Powering up remotely

Ian Evans dheianevans at gmail.com
Wed Sep 23 20:41:54 UTC 2020

On Tue, Sep 22, 2020 at 10:34 PM Christopher Sean Hilton <chris at vindaloo.com>

> On Tue, Sep 22, 2020 at 12:15:19PM -0400, Ian Evans wrote:
> >
> > ============================================================
> >
> > On Mon, Sep 21, 2020 at 7:02 PM jam at tigger.ws <jam at tigger.ws> wrote:
> >
> >
> >
> >     > On 22 Sep 2020, at 2:13 am, Ian Evans <dheianevans at gmail.com>
> wrote:
> >     >
> >     > 1) Let's say it auto-started but is currently sitting there
> >     >    with some "press y to continue" drive/os message. To future
> >     >    proof this, aren't there some motherboards that allow you
> >     >    to have remote KVM access through the bios?
> >
> >     There are grub kernel settings
> >     fsck=force fsck=repair
> >
> >     The logic being either the disk is trashed and saying y or n
> >     during fsck wont help you, or saying y will fix your disk. In
> >     any event (no spinning rust) I do noy find fsck obtrusive. Im
> >     using EXT4
> >
> I'm curious to see what this is when you get back to investigate. In
> my experience it could be something very simple. In my recent
> experience it wasn't but that's another story. The sequence of events
> to restore power for systems held can be more complicated than it
> would seem. Failures in the process could lead to a remote machine
> being in a safe completely off state.
> Three things might help you here:
> - IPMI
> - A remote switchable AC power unit
> - A Serial Console on your MythTV and a "terminal server"
> If you had either IPMI or a Serial console and a remote switchable
> plug for your MythTV server, you would have some options. IPMI is what
> you are talking about. It lets you get into your server before the
> operating system boots up. A remote switchable power plug would let
> you turn the server off and on from a remote location. Assuming the
> BIOS is setup to automatically turn the power on after a power cut,
> that should boot the server. A serial console and a terminal server
> from which to access it would allow you to control the server after
> the operation system boots even if it gets stuck before being able to
> go multi-user. If your server has a serial console which
> you can access remotely, you can use the serial console to answer the
> fsck questions and possibly fix the filesystem and then transition
> back to running.
> Without going into great detail, there are plenty of remote switchable
> AC plugs that you can find. So long as you can figure out a way to
> remotely access it from the internet, that would help. Best here would
> be something like an APC AP7900 Switchable PDU. You can get those on
> eBay for between US $50 and $120. I'm assuming that you are in the US
> here. I don't know what they would go for on the other side of the
> pond.
> As for serial consoles, they should be possible in Linux. My rough
> guess as to cost is again about $100. This sounds expensive but you
> need both a serial console and another server from which you access
> the console. My $100 estimate:
> - puts a PCIe serial card in your MythTV;
> - purchases a Raspberry Pi and the other dedicated hardware that you
>   need to access the MythTV console.
> The basic operation would then be to use ssh into the raspberry
> pi; then use a serial access program like `cu` to jump from the pi's
> ssh command line to the serial console.
> In summary, there's no way to know what the right solution is until
> you get back home because right now you don't know enough about how
> the system failed.
Once again to everyone: Thanks for the input, advice, and food for thought.

Christopher: Yes, the suspense is killing me. The one or two times this
happened over the last nine years it was always some fsck/error type
message for the recording drives (two internal and an external drive I send
some stuff to after recording). It had never been the OS drive. So it's
sorta frustrating that the boot process will hang (and ssh not start)
because of something happening to a data drive. You'd think it would let
you get to the point where you could ssh in and then say "Here's a problem
with your system. I can't continue past this." It'll be a while before I
see it and if it's just a "hit y" wait a few minutes and bingo, I'll yell.

I really like the console idea as I was thinking of doing a project with a
Pi anyway and that could be one of its purposes. Question: Is it something
that you can ssh into, run the console terminal, and see the output so far,
or is it a matter of 1) ssh into the Pi, start the console, 2) use remote
AC switch to restart mythbox 3) see that NEW output? I hope that was a
clear question.

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