Systemd mythbackend Configuration

From MythTV Official Wiki
Revision as of 12:58, 12 December 2017 by Stevegoodey (talk | contribs) (Minor formatting change.)

Jump to: navigation, search

Some newer Linux distributions (including Ubuntu 15.04 onwards) replace the traditional LSB init script startup management process with a program called systemd, which does things differently; here are some notes on how to make MythTV play nicely with systemd. A cheatsheet from the traditional init scripts to systemd is available on the Fedora wiki pages.

Note that much of the example startup code that follows is based on the rpmfusion packaging of MythTV by Richard Shaw.

Warning.png Warning: There should be exactly one .service name for MythTV. mythtv-backend.service is popular, but mythbackend.service is mentioned here. Choose whatever name you like, just don't have two (it's ok to have one in /lib/systemd/system and one in /etc/systemd/system that overrides it as long as the names are identical.)

Default configuration

Save the configuration file below in /etc/systemd/system/mythbackend.service Changes to files in /lib/systemd/system will be over-written when updated.

Script.png /etc/systemd/system/mythbackend.service

# Do not edit this file, it will be replaced on update
# If you need to make modifications to this unit file first make a copy in # /etc/systemd/system

# This file is part of the packaging of MythTV #
# MythTV is free software; view for more information.
# It is sometimes necessary to wait for a capture device to finish (hot)plug
# initialization before the backend starts.  If this is necessary, 
# create a Wants and After entry for all the capture devices that
# one wishes to wait to be created before the backend starts using the systemd
# device name mangling names (/dev/some/thing turns 
# into dev-some-thing.device).  These normally should  be udev persistent 
# filename rules to avoid confusion.
# See the MythTV wiki for udev persistent filename # discussions found at:
# In order to insure that systemd will create a device unit for the 
# capture device, one must insure that udev will have the tag "systemd"
# (i.e. add TAG+="systemd" to the udev rule).
# The MythTV package ships with a default udev rule file located in: 
# /lib/udev/rules.d/99-mythbackend.rules

Description=MythTV backend service mysqld.service NetworkManager-wait-online.service pingnetwork.service

# Uncomment the following line if you will be using the mythweb plugin on the 
# same system as mythbackend.

# You have 2 choices for 'Type': simple or forking 
# These require ExecStart lines which are NOT interchangeable.
# Type=simple is recommended. 
# If using 'Type=simple'
# 1) you cannot have --daemon in the command line 

# If using 'Type=forking'
# 1) you must have --daemon in the command line AND
# 2) you must have  --pidfile /somewhere in the command line AND
# 3) you must have a line PIDFILE=/somewhere in the [service] stanza
# this lets systemd know how to find the forked process PID, 
# otherwise it presumes the starting process will be the remaining process
# (cf. with the mysqld_safe process which starts mysqld and then disappears).
# Specifying a pidfile with Type simple does not cause any problems and
# may help in debugging startup failures.


# Default setting assumes a system wide install. Otherwise it should be set to 
# the folder containing the .mythtv subfolder containing the config.xml file 
# Such as
# or

# systemd changes execution from the calling user (possibly root) to this user
# if you have permissions problems or obscure errors try logging in as mythtv 
# See notes below

# Uncomment one of the following...
# Use sysloging rather than separate logging:
#ExecStart=/usr/bin/mythbackend --syslog local7 

# If Type=forking you must specify the --daemon and --pidfile options:
#ExecStart=/usr/bin/mythbackend --daemon --logpath /var/log/mythtv --loglevel crit --pidfile /run/mythtv/ 

# Systemd sends stdout to syslog, and mythbackend has console logging enabled without --daemon.
# Send stdout to /dev/null so console logging doesn't go to syslog
# Default setting for Type=simple.
ExecStart=/usr/bin/mythbackend --logpath /var/log/mythtv --loglevel crit

# Whether systemd will continue over-watch and restart on any halt


Important.png Note: Starting with 0.25, there has been a change in the logging. You must adjust the ExecStart line above based on the active release and logging preference (in 0.25 and later.) See: Logging for details.

To enable the backend to start at the next boot, issue the command 'systemctl enable mythbackend.service'. To start the backend immediately, issue the command 'systemctl start mythbackend.service'.

If you specify a log file, all logging will be to that file. If you specify a logpath each program will write to distinctly named files: much better for debugging. Loglevel determines what is logged. Log messages at lower levels will be discarded: In descending order: emerg, alert, crit, err, warning, notice, info, debug. Defaults to info.

Important.png Note: The example runs the backend as user mythtv. You will need to insure that your files/directories/capture cards can be accessed by the mythtv user, or run the backend as root (not recommended). The following script snippet creates and sets the ownership and permissions for the logging folders.

# Sanity check on required folders
if [ ! -x /var/log/mythtv ]; then
# make logging folder
mkdir -p -m 755 /var/log/mythtv
chown -hR mythtv:mythtv /var/log/mythtv
# make pid folder
mkdir -p -m 755 /run/mythtv
chown -hR mythtv:mythtv /run/mythtv

If you have any problems with /run/mythtv not being created, try using /var/log/mythtv as the pidfile folder. Remember to check the ownership and permissions of any tuner sockets in /dev such as /dev/dvb or /dev/video. The mythtv user must be able to access them.

Another example for an ubuntu configuration

Please check this file is suitable for your requirements and edit where necessary.

Save the first configuration file below in /etc/systemd/system and the second in /etc/systemd/system/mythbackend.service.d. If you have been using mythbuntu check that there are no mythtv-backend.service files here or in /lib/systemd/system.

This isolates all configuration related to the startup of mythbackend within systemd configuration files.

It can also be used on other distibutions using systemd. But check on the locations of systemd unit files.

Script.png /etc/systemd/system/mythbackend.service

Description=MythTV backend service
# The following line will cause mythbackend to be terminated if the database dies.
# If you do not want this then use a weaker binding such as "Requires" or "Wants".

# Persistently named adapters
# Needs a systemd tag added to your udev persistent naming rules

# Wait for a dbus notification from mythbackend before starting other services
# This is enabled by default 0.28 onwards (may be in 0.27 as well)
# To disable this change type to simple

# Allow core dumps
# The core resource limit on the user specified below can reduce what
# is specified here. So it needs to be set as well.



ExecStart=/full/path/to/mythbackend $MYTHBACKEND_ARGS


Script.png /etc/systemd/system/mythbackend.service.d/environment.conf

# Command line arguments to be passed by systemd to mythbackend on startup.
# This variable must be defined or the service will not start.
Environment="MYTHBACKEND_ARGS=--logpath=/home/roger/logs --verbose=none,dvbsicache,tempdebug:debug"

# Environment variables for the mythbackend program itself

Allow the backend to restart on failure

Sometimes the backend will coredump in the middle of a firewire recording, for example. Or it just gets tired after a while and coredumps. Restarting it can clear things up, and pick up a recording where it left off (minus restart time). If you're there to restart it. SystemD can restart the backend with a simple setting and manual backend restart.

Script.png /etc/systemd/system/mythbackend.service

# Whether systemd will continue over-watch and restart on any halt

Delay starting the backend until tuners have initialized

Some tuners take a long time to initialize (typically, firmware loading) and may therefore not yet be available when the backend starts. Since the backend checks for the presence of tuners upon startup, tuner initialization needs to be completed before the backend is started.

This can be accomplished by adding additional Wants= and After= stanza to the unit file, but to have systemd create device units, you must first add a rule to the udev rules directory.

Script.png /etc/udev/rules.d/99-mythbackend.rules

# Create systemd device units for capture devices
SUBSYSTEM=="video4linux", TAG+="systemd"
SUBSYSTEM=="dvb", TAG+="systemd"
SUBSYSTEM=="firewire", TAG+="systemd"

With the udev rule tag, systemd will create a device unit at startup that one can add to the [Unit] stanza in the startup. Note that one must use the systemd mangled names (generally /dev/some/thing is mangled into dev-some-thing.device). It is highly recommended that you use udev persistent names rather than base names such as /dev/video0.

Script.png device wait code for a typical v4l2 device


Script.png device wait code for a typical dvb device


From mythtv-users post from Richard Shaw

Systemd has a built-in timeout on device units so that startup will not wait forever for a failed device startup.

There are many options for how to run mythbackend with SystemD but one decision you

  • MUST*
  • MUST*
  • MUST*

make is if you're going to run:




If you use Type=simple (which is my recommendation) then you *CANNOT* use the "--daemon" option because SystemD is not expecting the daemon to fork!!!

If you use Type=forking then you *MUST* use the "--daemon" option as well as specify a PID file, "--pidfile" in ExecStart *AND* you must set the PIDFile= systemd option so it knows where to find the PID file.

Someone please fix the wiki!

Thanks Richard

Delay starting the backend until network has initialized

The addition of pingnetwork.service to both a "Wants=" and "After="
line in the [Unit] section of mythbackend.service should greatly 
improve/eliminate mythfrontend clients failure to connect to the 

As user "root", enable the service: systemctl enable pingnetwork.service

Reference     : mythtv ticket #11160
Fedora 18 rpms: NetworkManager-
              : systemd-197-1

If remote clients/mythfrontend fail to connect to mythbackend, on the 
machine hosting mythbackend, examine /var/log/boot.log for a failed 
"Network Manager Wait Online" service, or execute "systemctl status 
NetworkManager-wait-online.service" and look for failure due to timeout.

cp -iv /usr/lib/systemd/system/NetworkManager-wait-online.service \

# Edit /etc/systemd/system/NetworkManager-wait-online.service to extend the
# timeout value. Doubling the default to 60 is suggested.

vi /etc/systemd/system/NetworkManager-wait-online.service

ExecStart=/usr/bin/nm-online -q --timeout=60

Reboot and check boot.log or use systemctl command above to check for the
successful execution of NetworkManager-wait-online.service. Increase the
timeout value if necessary and reboot.

Below is a status report of success:         
systemctl status NetworkManager-wait-online.service
NetworkManager-wait-online.service - Network Manager Wait Online
          Loaded: loaded (/etc/systemd/system/NetworkManager-wait-online.service; enabled)
          Active: inactive (dead) since Tue 2013-02-02 15:31:44 EST; 2min 16s ago
         Process: 827 ExecStart=/usr/bin/nm-online -q --timeout=60 (code=exited, status=0/SUCCESS)

Feb 02 15:31:11 stumble systemd[1]: Starting Network Manager Wait Online...
Feb 02 15:31:44 stumble systemd[1]: Started Network Manager Wait Online.

Quickly terminate mythbackend

If “systemctl stop mythbackend” takes 90 seconds to complete, the mythbackend
process is being shut down uncleanly. One could add “TimeoutStopSec=5” to the
[Service] section of the mythbackend.service file, but this would still kill
mythbackend abruptly. One reason for smoothly shutting down mythbackend would
be to enable use of a program profiler such as the GNU profiling tool gprof.

One solution:
1) add “--pidfile /var/log/mythtv/” to your ExecStart line in 
mythbackend.service (if necessary).

2) Change/Add the ExecStop line in the same file's [Service] section to:

3) Create /usr/local/bin/mythbackendstop. Make the script executable.
# Custom stop script to execute `kill -15` twice (which mythbackend
# apparently needs to exit cleanly)
KILLIT=`/usr/bin/cat /var/log/mythtv/` 
/usr/bin/kill -15 $KILLIT;/usr/bin/sleep 2;/usr/bin/kill -15 $KILLIT

Once properly set up, “systemctl stop mythbackend” will terminate mythbackend
in just a few seconds.

Logging to systemd journal

Mythbackend can be configured to log to the systemd journal. To do this add the parameter
to the startup command line. Mythbackend sets the SYSLOG_IDENTIFIER to the name of the program (by default "mythbackend"). So the log can be easily viewed by the command.
journalctl SYSLOG_IDENTIFIER=mythbackend