Diagnostic log file Output.log

The Output.log diagnostic log file contains status information, warnings, error messages, and debugging messages. It offers a lot information of the boot up and operation of a controller of the PLCnext family. It is a good compromise between information and system performance.
You will find the file in the /opt/plcnext/logs folder on the file system of your controller. The file system can be accessed via the SFTP protocol. The SFTP client software is required for this (e.g., WinSCP).
The diagnostic log file Output.log is configured as a rolling file in the configuration file /etc/plcnext/Device.log.ini. If the file is > 16 MB, old log messages are stored in a separate file. These separate files are created with an index starting from 1, e.g. /opt/plcnext/logs/Output.log.1. Every file with an index can be copied for evaluation.

The diagnostic log file contains the following message types:

  • Error & Fatal: If messages of the Error or Fatal type are issued, the controller is stopped. The errors mainly arise during startup, or during execution of a user program.
  • Warning: Messages of type Warning indicate potentially occurring errors.
  • Information: The core components issue messages of the Information type. These provide an overview of the system status.

Example of an Output.log diagnostic log file:Click to show an example of an Output.log diagnostic log file

18.05.07 08:24:15.830 MyLibrary.MyComponent INFO 'MyComponent' invoked of object with instance name 'MyLibrary.MyComponent-1'
18.05.07 08:24:15.831 Arp.Plc.Plm.Internal.PlmManager INFO Component 'MyLibrary.MyComponent-1' from library 'MyLibrary' created. 
18.05.07 08:24:15.831 MyLibrary.MyComponent INFO 'Initialize' invoked of object with instance name 'MyLibrary.MyComponent-1'
18.05.07   08:24:15.832  MyLibrary.MyComponent INFO 'SubscribeServices' invoked of object with in­stance name 'MyLibrary.MyComponent-1'
18.05.07 08:24:15.832  MyLibrary.MyComponent INFO Component 'AcfDemo' not found!
18.05.07  08:24:15.833  MyLibrary.MyComponent INFO  'LoadSettings' invoked of object with instance name 'MyLibrary.MyComponent-1' 
18.05.07  08:24:15.833  MyLibrary.MyComponent INFO  'SetupSettings' invoked of object with instance name 'MyLibrary.MyComponent-1'


MyLibrary.MyComponent INFO 'LoadConfig' invoked of object with instance name 'MyLibrary.MyComponent-1'
18.05.07  08:24:15.834 MyLibrary.MyComponent INFO 'SetupConfig' invoked of object with instance name 'MyLibrary.MyComponent-1'
18.05.07 08:24:15.988 MyLibrary.MyComponent.MyProgram INFO Added Port 'zaehler (of Data Type 8)' of instance MyLibrary.MyComponent-1/MyProgram1
18.05.07 08:24:15.989 MyLibrary.MyComponent.MyProgram INFO Added Port 'zaehler (of Data Type 8)' of instance MyLibrary.MyComponent-1/P1
18.05.07 08:24:16.121 Arp.Io.Axioline.AxiolineComponent INFO Axioline: Load configuration.
18.05.07 08:24:16.127 Arp.Io.Axioline.AxiolineComponent INFO AxiolineComponent::LoadPlc() Path=/opt/plc­next/projects/PCWE/Io/Arp.Io.AxlC/links.xml



Date of the message in the format DD.MM.YY


Time of the message in the format hh:mm:ss.ms


Component that triggers the message


Message type (log level)


Message, e.g., info text, error message, debugging message

Enhanced Debug Log

Note: Activate the enhanced PLCnext Debug Log mode only if you are requested to do so by the support.

For a deeper insight into the system, it is possible to activate an extended log mode. In addition to the messages of typeError,  Warning, and Information, this also displays the developmentDebug messages. To activate the extended mode, change the configuration of the /etc/plcnext/Device.log.ini (e.g. /etc/plcnext/AXCF2152.log.ini) as follows.

Note: The enhanced logging generates a higher system load that might influence the timing of running applications.
Phoenix Contact strongly recommends to deactivate the enhanced logging after usage.



For the modification of the *.log.ini (e.g. AXCF2152.log.ini) a root user is necessary. How to create a root user can be read here. Be sure to observe all warnings.

  • Open the configuration file *.log.ini (e.g. AXCF2152.log.ini) on the file system of your controller under \etc\plcnext.
  • Change the threshold key from INFO to  DEBUG as in the following example:

log4cplus.rootLogger=DEBUG, ConsoleAppender1, RollingFileAppender1, SysLogAppender1

log4cplus.appender.SysLogAppender1.Appender.layout.ConversionPattern=%c %p - %m%n

log4cplus.appender.ConsoleAppender1.Appender.layout.ConversionPattern=%d{%d.%m.%y %H:%M:%S.%q} %-30.30c %-5p - %m%n

log4cplus.appender.RollingFileAppender1.Appender.layout.ConversionPattern=%d{%d.%m.%y %H:%M:%S.%q} %-60c %-5p - %m%n

  • After you have changed the configuration file, save the changes and reboot the controller.

The enhanced logging is now active and the message type DEBUG is now available in the Output.log file as in the following example:

30.11.17  16:23:07.263  OpcServer INFO  

OPC UA server opened endpoint URI opc.tcp://axc-f-2152-1:4840 listening at opc.tcp://

30.11.17  16:23:07.264 Arp.Services.OpcUAServer.Internal.Security.SessionManager DEBUG Start - ENTRY
30.11.17  16:23:07.264 Arp.Services.OpcUAServer.Internal.Security.SessionManager DEBUG Start - creating new thread
30.11.17 16:23:07.265 Arp.System.Rsc.ServiceManager DEBUG Create local service 'Arp:Arp.System.Um.Services.Internal.IPasswordAuthenticationService'
30.11.17 16:23:07.267 Arp.Services.OpcUAServer.Internal.Security.SessionManager DEBUG Start - new thread is started
30.11.17 16:23:07.268 Arp.Services.OpcUAServer.Internal.Security.SessionManager DEBUG Start - RETURN
30.11.17 16:23:07.267 Arp.System.Commons.Threading.Thread DEBUG Thread 'OpcUAServer::Se' starts.
30.11.17 16:23:07.269 Arp.Services.OpcUAServer.OpcUAServerComponent DEBUG StartPlc - RETURN
30.11.17 16:23:07.270 Arp.System.Acf.Internal.Sm.ComponentsController DEBUG Started component'Arp.Services.OpcUAServer' in process 'MainApplication'.
30.11.17 16:23:07.271 Arp.System.Acf.Internal.Sm.ComponentsController DEBUG Starting component 'Arp.Services.ProfiCloud' in process 'MainApplication'.
30.11.17 16:23:07.272 Arp.Services.ProfiCloud.ProfiCloudComponent DEBUG StartPLC - Starting Proficloud connection
30.11.17 16:23:07.272 Arp.Services.ProfiCloud.Internal.ProficloudTSDAdapter INFO

No metrics configured. Will not connect to Proficloud.

30.11.17 16:23:07.273 Arp.System.Acf.Internal.Sm.ComponentsController DEBUG Started component'Arp.Services.ProfiCloud' in process 'MainApplication'.
30.11.17 16:23:07.275 Arp.System.Acf.Internal.Sm.ComponentsController DEBUG Starting component 'Arp.Services.Wbm' in process 'MainApplication'.
30.11.17 16:23:07.276 Arp.System.Commons.Threading.Thread DEBUG Thread 'SessionTimeoutW' starts.
30.11.17 16:23:07.277 Arp.System.Acf.Internal.Sm.ComponentsController DEBUG Started component'Arp.Services.Wbm' in process 'MainApplication'.
30.11.17 16:23:07.279 Arp.System.Acf.Internal.ApplicationBase INFO Application 'MainApplication' was setup successfully.
30.11.17 16:23:07.279 Arp.Device.HmiLed.Internal.LedManager DEBUG Receive State 0x00000003 from Arp.System.Acf.Internal.Sm.SystemManager
30.11.17 16:23:07.277 Arp.System.Commons.Threading.Thread DEBUG Thread 'WbmFcgiServerTh' starts.

Template Loggable

You can apply tags to log messages from components, programs or other code elements. See  Common classes for more information.




•  Web browser recommendation: Chrome/Edge 88 or newer, Firefox ESR 90 or neweror Safari • 
• Published/reviewed: 2022-09-14 • Revision 046 •