The Systemd Journal is a database file that contains all the system logs. In certain conditions it may be useful to be able to access a file dump of the journal content, for example for debugging purposes.
To support this use case, two utilities are made available:

Eth_journalctl Utility

The eth_journalctl is a utility script that is installed by ESF and available in the /usr/bin folder of the gateways.
It wraps the system journalctl utility providing more functionalities, mainly ESF oriented, in order to have a log representation similar to what usually observed in the kura.log file.

A description of the usage can be obtained invoking the eth_journalctl -help command:

root@boltgate2031-64:~# eth_journalctl -help

Usage: /usr/bin/eth_journalctl [-e] [-k] [-d destination file] [-u unit] [-o output format] [-f FIELD1,..,FIELDN] [-x extra-vars]
	-k enables continuous printing of new entries as they are appended to the journal. (Optional)
	-d the destination file to save the journald logs.
	-u the optional systemd unit or pattern to be used to filter the journal entries. Set to - to select all units.
	-o the output format. Supported options are: short, short-full, short-iso, short-iso-precise, short-precise, short-monotonic, short-unix, verbose, export, json, json-pretty, json-sse, cat, with-unit. Default: short
	-f a comma separated list of the fields which should be included in the output. This has an effect only for the output modes which would normally show all fields. (Optional)
	-e Selects suitable options for displaying ESF logs. This allows to print log4j logger name and exception stacktraces. Appends the "SYSLOG_IDENTIFIER,PRIORITY,ESF_LOGGER,MESSAGE,STACKTRACE" fields to current selection (see -f option), changes the output format to "verbose" and the unit to "kura" if these parameters are not explicitly set (see the -o and -u options) (Optional)
	-x extra parameters (optional)
	-h show help

Following an example of usage:

root@boltgate2031-64:~# eth_journalctl -e

Tue 2020-08-04 18:52:28.247333 UTC [s=f4476e38d4ef4b0fa693f0d30f381734;i=9f9;b=b8ecf16d6831435795af1c259e68ac23;m=e4c1aff;t=5ac11c1bb39a7;x=e2167a62199f2c9b]
    PRIORITY=4
    SYSLOG_IDENTIFIER=ESF
    LOG4J_LOGGER=org.eclipse.kura.core.data.transport.mqtt.MqttDataTransport
    MESSAGE=xxxxx  Connect failed. Forcing disconnect. xxxxx
Tue 2020-08-04 18:52:28.255242 UTC [s=f4476e38d4ef4b0fa693f0d30f381734;i=9fa;b=b8ecf16d6831435795af1c259e68ac23;m=e4c39ff;t=5ac11c1bb58a5;x=c356e0af8284bc5b]
    PRIORITY=6
    SYSLOG_IDENTIFIER=ESF
    LOG4J_LOGGER=org.eclipse.kura.core.data.transport.mqtt.MqttDataTransport
    MESSAGE=Closing client...
Tue 2020-08-04 18:52:28.263201 UTC [s=f4476e38d4ef4b0fa693f0d30f381734;i=9fb;b=b8ecf16d6831435795af1c259e68ac23;m=e4c5919;t=5ac11c1bb77bd;x=44ec1c660d284dcd]
    PRIORITY=6
    SYSLOG_IDENTIFIER=ESF
    LOG4J_LOGGER=org.eclipse.kura.core.data.transport.mqtt.MqttDataTransport
    MESSAGE=Closed
Tue 2020-08-04 18:52:28.301470 UTC [s=f4476e38d4ef4b0fa693f0d30f381734;i=9fc;b=b8ecf16d6831435795af1c259e68ac23;m=e4cefac;t=5ac11c1bc0e5e;x=cd597b041c336854]
    PRIORITY=4
    SYSLOG_IDENTIFIER=ESF
    LOG4J_LOGGER=org.eclipse.kura.core.data.DataServiceImpl
    MESSAGE=Connect failed
    STACKTRACE=org.eclipse.kura.KuraConnectException: "Connection failed. Cannot connect"
               	at org.eclipse.kura.core.data.transport.mqtt.MqttDataTransport.connect(MqttDataTransport.java:341)
               	at org.eclipse.kura.core.data.DataServiceImpl$2.run(DataServiceImpl.java:605)
               	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
               	at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
               	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
               	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
               	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
               	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
               	at java.lang.Thread.run(Thread.java:748)
               Caused by: Unable to connect to server (32103) - java.net.ConnectException: Connection refused (Connection refused)
               	at org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:80)
               	at org.eclipse.paho.client.mqttv3.internal.ClientComms$ConnectBG.run(ClientComms.java:722)
               	... 1 more
               Caused by: java.net.ConnectException: Connection refused (Connection refused)
               	at java.net.PlainSocketImpl.socketConnect(Native Method)
               	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
               	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
               	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
               	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
               	at java.net.Socket.connect(Socket.java:589)
               	at org.eclipse.paho.client.mqttv3.internal.TCPNetworkModule.start(TCPNetworkModule.java:74)
               	... 2 more
Tue 2020-08-04 18:52:28.386296 UTC [s=f4476e38d4ef4b0fa693f0d30f381734;i=9fd;b=b8ecf16d6831435795af1c259e68ac23;m=e4e39dd;t=5ac11c1bd5884;x=6a92830a669cbb52]
    PRIORITY=6
    SYSLOG_IDENTIFIER=ESF
    LOG4J_LOGGER=AuditLogger
    MESSAGE=UI CloudConnection - Success - Successfully listed stack pids by factory for user: admin, session node0sias7bdsmkorxf41hb7o9ymq0
Tue 2020-08-04 18:52:28.634363 UTC [s=f4476e38d4ef4b0fa693f0d30f381734;i=9fe;b=b8ecf16d6831435795af1c259e68ac23;m=e52041f;t=5ac11c1c122d0;x=aaf76d431a20d4ce]
    PRIORITY=6
    SYSLOG_IDENTIFIER=ESF
    LOG4J_LOGGER=AuditLogger
    MESSAGE=UI Component - Success - Successfully listed component configs for user: admin, session node0sias7bdsmkorxf41hb7o9ymq0

Esf-journal-tools Docker Container

The esf-journal-tools is a docker container that provides the eth_journalctl capabilities to the developer workstation.
It allows to convert a journal database file retrieved from a gateway to a parseable text file even in non Linux systems like Mac or Windows.

The usage is the following:

the developer needs to download to his machine the gateway journal log file, for example using SSH
change his working directory to the one where the downloaded journal file is located
execute the following command:

docker run -v "$(pwd):/tmp/journal" --rm esf-journal-tools:latest

This will produce a resulting text file will all the logs in the original journal database file.