[mythtv-users] Can't start backend on Debian 9 (Stretch)

[Stephen Worthington]

On Thu, 27 Jul 2017 16:04:26 -0500, you wrote:

>On Thu, Jul 27, 2017 at 3:19 PM, Mike Perkins <mikep at randomtraveller.org.uk>
>wrote:
>
>> On 27/07/17 20:05, Ian Campbell wrote:
>>
>>> On Thu, 2017-07-27 at 19:59 +0100, Ian Campbell wrote:
>>>
>>>>
>>>> I would expect that even LSB compat based stuff would show up on
>>>> systemd based systems in things like "systemctl" and "system status"
>>>> output, and with that you should be able to find the name it has given
>>>> the compat unit for use with journalctl (I think it's "-u <unit>" to
>>>> inspect a particular unit, but I don't have a running systemd system to
>>>> check on).
>>>>
>>>
>>> I found a (non-myth) systemd system. On it I have:
>>>     $ sudo systemctl | grep LSB
>>>       cgroupfs-mount.service
>>>                                           loaded active exited    LSB: Set
>>> up cgroupfs mounts.
>>>       cpufrequtils.service
>>>                                           loaded active exited    LSB: set
>>> CPUFreq kernel parameters
>>>     ? docker.service
>>>                                           loaded failed failed    LSB:
>>> Create lightweight, portable, self-sufficient containers.
>>>
>>> I can examine the failed service with (sudo or you don't get logs, just
>>> the info):
>>>
>>>     $ sudo systemctl status docker.service
>>>     ? docker.service - LSB: Create lightweight, portable, self-sufficient
>>> containers.
>>>        Loaded: loaded (/etc/init.d/docker; generated; vendor preset:
>>> enabled)
>>>        Active: failed (Result: exit-code) since Sun 2017-06-11 13:27:42
>>> BST; 1 months 15 days ago
>>>          Docs: man:systemd-sysv-generator(8)
>>>       Process: 1501 ExecStart=/etc/init.d/docker start (code=exited,
>>> status=1/FAILURE)
>>>
>>> Jun 11 13:27:41 dagon systemd[1]: Starting LSB: Create lightweight,
>>> portable, self-sufficient containers....
>>> Jun 11 13:27:42 dagon docker[1501]: /usr/bin/docker not present or not
>>> executable ... failed!
>>> Jun 11 13:27:42 dagon systemd[1]: docker.service: Control process exited,
>>> code=exited status=1
>>> Jun 11 13:27:42 dagon systemd[1]: Failed to start LSB: Create
>>> lightweight, portable, self-sufficient containers..
>>> Jun 11 13:27:42 dagon systemd[1]: docker.service: Unit entered failed
>>> state.
>>> Jun 11 13:27:42 dagon systemd[1]: docker.service: Failed with result
>>> 'exit-code'.
>>>
>>> As you can see it is using an automatically generated unit file which
>>> is calling the LSB/sysvinit script (which is actually stale because
>>> docker isn't installed on this machine).
>>>
>>> I would expect you would find something similar based on
>>> /etc/init.d/mythtv-backend on your system, and probably some sort of
>>> error message.
>>>
>>> Yes, and that's what I did find, that systemd generates a temporary
>> .service file.
>>
>> Trouble is, the log lies:
>>
>> root at jade:/home/micheal# systemctl status mythtv-backend
>> ? mythtv-backend.service - LSB: Start/Stop the MythTV server.
>>    Loaded: loaded (/etc/init.d/mythtv-backend; generated; vendor preset:
>> enabled)
>>    Active: active (exited) since Thu 2017-07-27 15:42:01 BST; 5h 24min ago
>>      Docs: man:systemd-sysv-generator(8)
>>     Tasks: 0 (limit: 4915)
>>    CGroup: /system.slice/mythtv-backend.service
>>
>> Jul 27 15:41:56 jade systemd[1]: Starting LSB: Start/Stop the MythTV
>> server....
>> Jul 27 15:42:01 jade mythtv-backend[706]: Starting MythTV server:
>> mythbackend .
>> Jul 27 15:42:01 jade systemd[1]: Started LSB: Start/Stop the MythTV
>> server..
>> root at jade:/home/micheal#
>>
>> Unfortunately, 15:42 is the time I shut down the working system before I
>> redid the database. Apart from the time I ran it manually, all attempts to
>> start or restart mythtv-backend produce exactly nothing. NO activity I did
>> afterwards appears to exist in the logs, such as I could figure out of them.
>
>
>Just a quick note - I am sure you have tried, but I should mention it.  If
>you try to stop a service with systemd (systemctl) that was not started
>with systemctl, systemd will silently not stop it for you.  If mythbackend
>is not running, systemd should start it though (in a perfect world where
>units exist, etc)..
>
>Just tossing that out in case you already had it running and tried to stop
>it with systemd.

Actually, the whole systemd support for System V init scripts is buggy
and very difficult to work with.  Debugging an init script under
systemd requires using workarounds that make life difficult.  It is
much better to install a proper .service file and use systemd as it is
meant to be used.  Init scripts often just silently fail to start,
stop or anything else they are supposed to do when used with systemd
if something goes wrong.

So, if there is no /lib/systemd/system .service file installed by your
packages, then you should install one yourself manually to
/etc/systemd/system and remove the /etc/init.d/ script (by renaming it
if you want to keep it around for reference - add .save to the end of
the name).  Then run systemctl daemon-reload and try using the new
.service file.

This is what Mythbuntu uses for /lib/systemd/system/mythbackend.conf:

[Unit]
Description=MythTV Backend
Documentation=https://www.mythtv.org/wiki/Mythbackend
After=mysql.service network.target

[Service]
User=mythtv
EnvironmentFile=-/etc/mythtv/additional.args
ExecStart=/usr/bin/mythbackend --quiet --syslog local7
$ADDITIONAL_ARGS
StartLimitBurst=10
StartLimitInterval=10m
Restart=on-failure
RestartSec=1

[Install]
WantedBy=multi-user.target

That works as long as you are not using external networking with
mythbackend, such as network tuners or external frontends.  If you are
using external networking, then this should work, as long as you are
using Network Manager for your networking:

[Unit]
Description=MythTV Backend
Documentation=https://www.mythtv.org/wiki/Mythbackend
Wants=NetworkManager-wait-online.service
After=mysql.service network.target NetworkManager-wait-online.service

[Service]
User=mythtv
EnvironmentFile=-/etc/mythtv/additional.args
ExecStart=/usr/bin/mythbackend --quiet --syslog local7
$ADDITIONAL_ARGS
StartLimitBurst=10
StartLimitInterval=10m
Restart=on-failure
RestartSec=1

[Install]
WantedBy=multi-user.target

With this .service file, in your /etc/mythtv directory you can put a
file additional.args if you need to add things to the mythbackend
command line.  Mine looks like this:

#ADDITIONAL_ARGS=-v all --loglevel debug
ADDITIONAL_ARGS=-v record,dvbcam

The .conf files need to be set to chown root:root and chmod
u=rw,g=r,o=r.

I do not know if the NetworkManager-wait-online.service is enabled by
default in Debian, so you should also do:

systemctl enable NetworkManager-wait-online.service

to make sure it is.

I find that typing "systemctl" and "journalctl" all the time is a big
pain, so this is what I have in my /root/.bash_aliases file now:

alias sc='systemctl'
alias jc='journalctl'
alias sco='systemctl stop'
alias scs='systemctl start'
alias scr='systemctl restart'
alias scst='systemctl status'