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

[Jim Abernathy]

On 7/27/20 12:34 PM, James Abernathy wrote:
>
>
>     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

Stephen,

So I've created the wait-for-ping stuff from your server. Do I still 
need my override conf file with:

    [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


My guess is I don't need the After=NetworkManager-wait-online.serivce 
since I have the wait for ping stuff.

Jim A



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