[mythtv-users] udev and systemd requirements for MythTV on Ubuntu 20.04?

[James Abernathy]

On Mon, Jul 27, 2020 at 12:16 PM Stephen Worthington <
stephen_agent at jsw.gen.nz> wrote:

> On Mon, 27 Jul 2020 10:43:53 -0400, you wrote:
>
> >I'm doing some planning for moving from MythTV v31 on Ubuntu 18.04 to
> >MythTV v31 on Ubuntu 20.04.  There are a lot of considerations, like my
> >current system using MariaDB and the current issue regarding that on
> Ubuntu
> >20.04.
> >
> >However, my concerns today are related to udev rules and systemd
> overrides.
> >
> >On my 18.04 system, I have one udev rule related to mythtv;
> >99-mythbackend.rules
> >
> >SUBSYSTEM=="video4linux", TAG+="systemd"
> >SUBSYSTEM=="dvb", TAG+="systemd"
> >SUBSYSTEM=="firewire", TAG+="systemd"
> >
> >When I installed mythtv v31 on a virtual machine of Ubuntu 20.04, this
> file
> >was not there. I probably created it myself because of the Hauppauge WinTV
> >HD Quad PCIe tuner card I was using.
> >
> >So is this still necessary for Ubuntu 20.04 and mythtv v31?
> >
> >Also,  on my current system I have an override file in
> >/etc/systemd/system/mythtv-backend.service.d/ythtv-backend-override.conf:
> >[Unit]
> >Wants=dev-dvb-adapter0-frontend0.device
> >After=dev-dvb-adapter0-frontend0.device
> >Wants=dev-dvb-adapter1-frontend0.device
> >After=dev-dvb-adapter1-frontend0.device
> >Wants=dev-dvb-adapter2-frontend0.device
> >After=dev-dvb-adapter2-frontend0.device
> >Wants=dev-dvb-adapter3-frontend0.device
> >After=dev-dvb-adapter3-frontend0.device
> >
> >After=NetworkManager-wait-online.service
> >
> >I figure this is also related to the Hauppauge card and also my HDHomerun
> >tuner.
> >
> >Again I think I did this back with mythtv29 and it's stayed through the
> >upgrades to v31.
> >
> >Do I need any of this in mythtv v31 on Ubuntu 20.04?
> >
> >On the Ubuntu 20.04 test virtual machine I have only the HDHR tuner and it
> >works fine but I have no udev rules or systemd override file.
> >
> >Thoughts?
> >
> >Jim A
>
> You will have created those udev rules and the override file manually.
>
> Those udev rules create the .device targets.  The reason for having
> those targets is that it is possible for mythbackend to start before
> the tuners are created, and having it wait on the device targets
> prevents that.  If mythbackend starts before a tuner is working, when
> it tests the tuner at startup that tuner will not work and mythbackend
> will mark it as failed and not test it again until the next startup of
> mythbackend.
>
> If you only have the one tuner in the 20.04 system, you need to
> comment out all the Wants/After lines referring to non-existent
> tuners.  Otherwise mythbackend will only start after a very long
> timeout waiting for those tuners.
>
> It was very interesting when I deleted all my backend tuners recently and
added them back in on my 18.04 v31 system, I ended up with only one adapter
name and when I added all 4 there was only one name repeated 4 times.


> If you are using networked tuners such as HDHomeruns, you should have
> one of the fixes (such as mine) that prevents mythbackend from
> starting before the network us up enough for it to access the
> networked tuners.  Waiting for NetworkManager-wait-online.service is
> not sufficient to ensure that, and each version of Ubuntu tends to
> start up faster than the previous version, so mythbackend is getting
> started earlier and earlier.  So if it was working OK without such a
> fix in 18.04, it may not in 20.04.  It is best to use something that
> pings a networked tuner before it allows mythbackend to be started.
> Search this list's archives for "wait-until-pingable.py" to find the
> threads for my fix.
>
> And the speed of the SSD you have the system on also affects the
> startup speed.  A new system with a super fast M.2 NVMe SSD and lots
> of RAM can cause interesting surprises with how fast things start up.
>
> So it sounds like for 20.04, I'll continue to create the udev rules and to
be safe put back in the wait-for-ping stuff I had back in the v29 days.

I also noticed that Hauppauge Linux has added Ubuntu 20.04 to their list on
supported O/S's on their PPA (
https://hauppauge.com/pages/support/support_linux.html)

Jim A
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