Difference between revisions of "Logging"

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(explain how to get a full list of things that can be selected for more detailed logging)
(Teaser about 0.28-pre per component loglevels)
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0.28-pre is now allows users to set the loglevel on a per component basis, e.g.
mythbackend --setverbose upnp:debug,http:notice,record:debug
Detailed help information is available for each argument by including the argument name after <code>--help</code>, for example:
Detailed help information is available for each argument by including the argument name after <code>--help</code>, for example:

Revision as of 02:30, 11 November 2015

Current MythTV supports logging to various loggers. Logging options are specified with command-line arguments.

Important.png Note: Starting with version 0.26, all log requests are handled by the mythlogserver application, which is automatically started as needed. Logging arguments are still specified for mythbackend and mythfrontend applications and are passed to mythlogserver. With 0.27, mythlogserver is now optional and it appears many distributions are disabling it (or users can do that with the command line option --nologserver.) In such cases, logs are written by each MythTV program according to the parameters below.


All logging (regardless of specified logger) is affected by the arguments:

--loglevel                      Set the logging level.  All log messages at
                                lower levels will be discarded.
                                In descending order: emerg, alert, crit, err,
                                warning, notice, info, debug
                                defaults to info
-v OR --verbose                 Specify log filtering. Use '-v help' for level

Typically, the default value for --loglevel and --verbose are appropriate for normal application execution. However, you may be asked to provide logs at a specific log level when helping debug issues.

mythbackend's verbose and log levels can be changed on-the-fly (as opposed to stoping, changing and restarting it.) For example:

mythbackend --setverbose upnp
mythbackend --setloglevel debug

0.28-pre is now allows users to set the loglevel on a per component basis, e.g.

mythbackend --setverbose upnp:debug,http:notice,record:debug

Detailed help information is available for each argument by including the argument name after --help, for example:

mythbackend --help setloglevel
mythbackend --help logpath

Important.png Note: The legacy --logfile and -l arguments are no longer supported after 0.24. Any script using --logfile or -l to start MythTV applications must be updated.

The --setverbose argument provides fine-grained control over what kinds of things get extra logging. To get a full list of the options, run:

mythbackend -v help

Don't forget to comma-separate the items you select, for example:

mythbackend -v playback,upnp --loglevel debug   # at startup
mythbackend --setverbose playback,upnp          # on the fly


Console Logging

If running a MythTV application in a non-daemon mode, console logging will be enabled. Console logging is output to stdout.

Console logging is automatically disabled with the argument:

--daemon OR -d                  Fork application into background after startup.

(for MythTV daemon applications).

The console logging output contains a shortened format which better fits a standard terminal. Therefore, please provide full file logging output when attaching log files to bug tickets.

File Logging

The primary logger for MythTV applications is the file logger. File logging outputs detailed "debug" logging information about process execution, which can be very useful in debugging issues with MythTV. All log files uploaded to bug tickets should be those created from the file logger.

File logging is disabled by default and may be enabled with the argument:

--logpath                        Writes logging messages to a file in the directory logpath with
                                 filenames in the format: applicationName.date.pid.log.
                                 This is typically used in combination with --daemon, and if used
                                 in combination with --pidfile, this can be used with log
                                 rotators, using the HUP call to inform MythTV to reload the file

Important.png Note: File logging requires that the process writing the logs have permission on the specified logpath directory, as well as on the log files. This can be a challenge to configure properly in environments where different MythTV applications are run as different users. Since mythlogserver is spawned (and re-spawned) by whichever application needs it, mythlogserver may be run as different users at different times--even during a single MythTV session. Therefore, you may need to open up permissions or use newgrp to log in to a new group (a secondary group membership, such as mythtv) before starting the MythTV applications. Alternatively, you can use syslog logging.

File logging output may be challenging to read in a terminal due to the amount of information included. You may simplify the log file output with a log processor. For example, the command:

perl -pwe '$| = 1; s#^(\d{4}(?:-\d{2}){2} \d{2}(?:\:\d{2}){2}\.\d{6} \w) \[\d+/\d+\] \S+ \S+ \(\S+\) - (.*$)#$1  $2#' /path/to/logfile

will scan the log file at /path/to/logfile and output (to stdout) a simplified log format equivalent to that used by console logging. Change the /path/to/logfile, as appropriate for your system.

If you'd like to log full details while following the log file in a console with the above simplification, use the tail command:

tail -f /path/to/logfile | perl -pwe '$| = 1; s#^(\d{4}(?:-\d{2}){2} \d{2}(?:\:\d{2}){2}\.\d{6} \w) \[\d+/\d+\] \S+ \S+ \(\S+\) - (.*$)#$1  $2#'

syslog Logging

Logging to syslog may be enabled with the argument:

--syslog                        Set the syslog logging facility.
                                Set to "none" to disable, defaults to none

By default, logging to syslog is disabled. You should only enable syslog logging if you have also configured syslog on your host to handle the MythTV log messages appropriately. Logging to syslog allows (via syslog configuration) user-specified log file names.

Database Logging

Prior to 0.27, database logging is enabled by default. It may be disabled with the argument:

--nodblog                       Disable database logging.

With 0.27+, database logging is off. It can be turned on with:


MythTV automatically cleans up the database logging information, to ensure your database does not grow out of control. All database logging information is removed within 2 weeks, so database logging is primarily useful for short-term log access, and should not be considered a valid long-term logging mechanism.

Log file cleanup

You may configure external applications, such as logrotate or GNU Rottlog, to rotate your log files. These programs allow you to specify exactly how to handle the multiple log files--including how often to rotate, how many old log files to keep and how long to keep them, where to place the log files, whether to compress them, and much more. Example configurations are available in the Log Rotation Configuration Files category.

Alternatively, a python script, logcleanup.py, is available to manage the multiple copies of these logs generated each time the applications restart. With its default settings, it will keep a minimum of five sets of logs for each application, and each set will be kept a minimum of seven days. One log set is one file, along with any rotated, compressed copies generated by logrotate. This script can be set to run daily or weekly through cron.