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Viewing Logs when journald is Enabled

This page outlines journald and describes how to view logs when journald is enabled in webOS Open Source Edition (OSE).

Note
On webOS OSE 2.1.0 or higher, journald is enabled by default.

Overview of journald

journald is a system service for collecting and storing log data, introduced with systemd. journald runs as the systemd-journald daemon.

journald makes it easier for developers to find interesting and relevant information among an ever-increasing amount of log messages. It creates and maintains structured, indexed journals based on logging information that is received from a variety of sources so that you can check all the logs in sequence at once. The types of log data collected by journald are as follows:

  • Kernel log messages, via kmsg
  • Simple system log messages, via the libc syslog(3) call. In webOS OSE, these include the log messages formatted by PmLogLib.
  • Structured system log messages via the native Journal API, see sd_journal_print(3)
  • Standard output and standard error of service units
  • Audit records, originating from the kernel audit subsystem

For more information, see the official documentation.

Using journalctl to View Logs

To view logs when journald is enabled, use the journalctl command.

Note
This page covers only a part of journalctl. For a full desrciption of the command, see the journalctl documentation.

See All Messages

When run without any options, the journalctl command will show all journal entries.

root@raspberrypi4:/# journalctl

-- Logs begin at Mon 2019-08-26 18:11:58 PDT, end at Tue 2019-09-10 23:35:52 PDT. --
Aug 26 18:11:58 raspberrypi4 kernel: Booting Linux on physical CPU 0x0
Aug 26 18:11:58 raspberrypi4 kernel: [[0;1;39m[[0;1;31m[[0;1;39mLinux version 4.19.58 (oe-user@oe-host) (gcc version 8.2.0 (GCC)) #1 SMP Wed Jul 17 12:36:18 UTC 2019
Aug 26 18:11:58 raspberrypi4 kernel: CPU: ARMv7 Processor [410fd083] revision 3 (ARMv7), cr=30c5383d
Aug 26 18:11:58 raspberrypi4 kernel: CPU: div instructions available: patching division code
Aug 26 18:11:58 raspberrypi4 kernel: CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
Aug 26 18:11:58 raspberrypi4 kernel: OF: fdt: Machine model: Raspberry Pi 4 Model B Rev 1.1
Aug 26 18:11:58 raspberrypi4 kernel: Memory policy: Data cache writealloc
Aug 26 18:11:58 raspberrypi4 kernel: cma: Reserved 256 MiB at 0x000000001d000000
Aug 26 18:11:58 raspberrypi4 kernel: On node 0 totalpages: 447488
Aug 26 18:11:58 raspberrypi4 kernel:   DMA zone: 1629 pages used for memmap
Aug 26 18:11:58 raspberrypi4 kernel:   DMA zone: 0 pages reserved
Aug 26 18:11:58 raspberrypi4 kernel:   DMA zone: 185344 pages, LIFO batch:63
Aug 26 18:11:58 raspberrypi4 kernel:   HighMem zone: 262144 pages, LIFO batch:63

Check the Boot Messages

journald tracks each log to a specific system boot. To limit the logs shown to the current boot, use the journalctl command with -b option.

root@raspberrypi4:/# journalctl -b

-- Logs begin at Mon 2019-08-26 18:11:58 PDT, end at Tue 2019-09-10 23:35:52 PDT. --
Aug 26 18:11:58 raspberrypi4 kernel: Booting Linux on physical CPU 0x0
Aug 26 18:11:58 raspberrypi4 kernel: [[0;1;39m[[0;1;31m[[0;1;39mLinux version 4.19.58 (oe-user@oe-host) (gcc version 8.2.0 (GCC)) #1 SMP Wed Jul 17 12:36:18 UTC 2019
Aug 26 18:11:58 raspberrypi4 kernel: CPU: ARMv7 Processor [410fd083] revision 3 (ARMv7), cr=30c5383d
Aug 26 18:11:58 raspberrypi4 kernel: CPU: div instructions available: patching division code
Aug 26 18:11:58 raspberrypi4 kernel: CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
Aug 26 18:11:58 raspberrypi4 kernel: OF: fdt: Machine model: Raspberry Pi 4 Model B Rev 1.1
Aug 26 18:11:58 raspberrypi4 kernel: Memory policy: Data cache writealloc
Aug 26 18:11:58 raspberrypi4 kernel: cma: Reserved 256 MiB at 0x000000001d000000
Aug 26 18:11:58 raspberrypi4 kernel: On node 0 totalpages: 447488
Aug 26 18:11:58 raspberrypi4 kernel:   DMA zone: 1629 pages used for memmap
Aug 26 18:11:58 raspberrypi4 kernel:   DMA zone: 0 pages reserved
Aug 26 18:11:58 raspberrypi4 kernel:   DMA zone: 185344 pages, LIFO batch:63
Aug 26 18:11:58 raspberrypi4 kernel:   HighMem zone: 262144 pages, LIFO batch:63

View Messages in a Time Range

To see messages logged within a specific time window, you can use the -S and -U options. The following command shows journal messages logged within the last one hour.

root@raspberrypi4:/# journalctl -S "1 hour ago"

-- Logs begin at Mon 2019-08-26 18:11:58 PDT, end at Tue 2019-09-10 23:40:52 PDT. --
Sep 10 22:58:08 raspberrypi4 LunaSysService[832]: [] [pmlog] LunaSysService TIMEZONE_TRANSITION {"Abbr":"PST","DST":"End","Year":2019,"Time":1572771600,"Offset":-28800}
 TimeZone offset will be changed
Sep 10 22:58:08 raspberrypi4 LunaSysService[832]: [] [pmlog] LunaSysService TIMEZONE_TRANSITION {"Next":1572771600} TimeZone transition after 4590112 seconds
Sep 10 22:58:08 raspberrypi4 LunaSysService[832]: [] [pmlog] LunaSysService SYSTEM_TIME_UPDATED {"SOURCE":"ntp","PRIORITY":5,"NEXT_SYNC":1568181487} Updated system time
Sep 10 22:58:08 raspberrypi4 notificationmgr[984]: [] [pmlog] NOTIFICATION SYSTEMTIME_SYNC {"TIMESOURCE":"ntp","TIME":1568181488}
Sep 10 22:58:08 raspberrypi4 sleepd[700]: [[0;1;39m[[0;1;31m[[0;1;39mCould not open rtc driver. 2 2[[0m

The following command shows journal messages logged within the given time range.

root@raspberrypi4:/# journalctl -S "2019-09-10 23:40:00" -U "2019-09-10 23:43:00"

-- Logs begin at Mon 2019-08-26 18:11:58 PDT, end at Tue 2019-09-10 23:40:52 PDT. --
Sep 10 23:40:52 raspberrypi4 sleepd[700]: Could not open rtc driver. 2 2
Sep 10 23:40:52 raspberrypi4 sleepd[700]: Could not open rtc driver. 2 2
Sep 10 23:40:52 raspberrypi4 sleepd[700]: [] [pmlog] <default-lib> LS_REQUIRES_SECURITY {"SERVICE":"com.webos.service.power","CATEGORY":"/suspend","METHOD":"activitySt.
Sep 10 23:40:52 raspberrypi4 sleepd[700]: Could not open rtc driver. 2 2

View a Specific Number of Recent Logs

Like the tail command, the -n option will print the specified number of most recent journal entries.

root@raspberrypi4:/# journalctl -n 10 -S "1 hour ago"

-- Logs begin at Mon 2019-08-26 18:11:58 PDT, end at Tue 2019-09-10 23:45:52 PDT. --
Sep 10 22:58:08 raspberrypi4 LunaSysService[832]: [] [pmlog] LunaSysService TIMEZONE_TRANSITION {"Abbr":"PST","DST":"End","Year":2019,"Time":1572771600,"Offset":-28800d
Sep 10 22:58:08 raspberrypi4 LunaSysService[832]: [] [pmlog] LunaSysService TIMEZONE_TRANSITION {"Next":1572771600} TimeZone transition after 4590112 seconds
Sep 10 22:58:08 raspberrypi4 LunaSysService[832]: [] [pmlog] LunaSysService SYSTEM_TIME_UPDATED {"SOURCE":"ntp","PRIORITY":5,"NEXT_SYNC":1568181487} Updated system time
Sep 10 22:58:08 raspberrypi4 notificationmgr[984]: [] [pmlog] NOTIFICATION SYSTEMTIME_SYNC {"TIMESOURCE":"ntp","TIME":1568181488}
Sep 10 22:58:08 raspberrypi4 sleepd[700]: Could not open rtc driver. 2 2
Sep 10 22:58:08 raspberrypi4 ls-hubd[163]: [] [pmlog] ls-hubd LSHUB_NO_NAME_PERMS {} Can not find match for 'com.webos.notification' in pattern queue '["com.webos.sett'
Sep 10 22:59:39 raspberrypi4 login[281]: ROOT LOGIN  on '/dev/ttyS0'
Sep 10 23:00:52 raspberrypi4 sleepd[700]: Could not open rtc driver. 2 2
Sep 10 23:00:52 raspberrypi4 sleepd[700]: [] [pmlog] <default-lib> LS_REQUIRES_SECURITY {"SERVICE":"com.webos.service.power","CATEGORY":"/suspend","METHOD":"activitySt.
Sep 10 23:00:52 raspberrypi4 sleepd[700]: Could not open rtc driver. 2 2

Filter Messages by Unit

To see messages logged by any systemd unit, use the -u option.

root@raspberrypi4:/# journalctl -u bootd.service

-- Logs begin at Mon 2019-08-26 18:11:58 PDT, end at Tue 2019-09-10 23:45:52 PDT. --
Aug 26 18:12:12 raspberrypi4 systemd[1]: Starting webos - "bootd.service"...
Aug 26 18:12:12 raspberrypi4 sysctl[618]: kernel.randomize_va_space = 2
Aug 26 18:12:12 raspberrypi4 systemd[1]: Started webos - "bootd.service".
Aug 26 18:12:12 raspberrypi4 bootd[622]: [] [pmlog] bootManager Boot {"CLOCK":17.382,"PerfType":"Boot","PerfGroup":"Platform"} BOOTD_START
Aug 26 18:12:12 raspberrypi4 bootd[622]: [] [pmlog] bootManager Settings {} --DeviceType=raspberrypi4
Aug 26 18:12:12 raspberrypi4 bootd[622]: [] [pmlog] bootManager Settings {} --Distro=webos
Aug 26 18:12:12 raspberrypi4 bootd[622]: [] [pmlog] bootManager Settings {} --DistroVariant=normal
Aug 26 18:12:12 raspberrypi4 bootd[622]: [] [pmlog] bootManager Settings {} --NFSBoot=NO
Aug 26 18:12:12 raspberrypi4 bootd[622]: [] [pmlog] bootManager Settings {} --TimeDiff=0.0(s)
Aug 26 18:12:14 raspberrypi4 bootd[622]: [] [pmlog] bootManager BootSequencer {} Launch first app (bareapp)

Filter Messages by Priority

Use the -p option to filter messages based on their priority level.

The table below shows a list of priority levels. The default level is “info”.

Priority LevelRemarks
0 or "emerg"Emergency. The maximum level.
1 or "alert"Alert
2 or "crit"Critical
3 or "err"Error
4 or "warning"Warning
5 or "notice"Notice
6 or "info"Info. The default level.
7 or "debug"Debug

If a single priority level is specified, all messages with that priority level and below are returned. For example, when 2 or "crit" is specified, the messages from 0 to 2 ("emerg", "alert", "crit") are returned.

root@raspberrypi4:/# journalctl -p "crit"

To use a range of priority levels, provide the start and end levels in the form of FROM..TO. As an example, the command below will output all messages with priority between alert and critical.

root@raspberrypi4:/# journalctl -p "alert".."crit"

Change the Format of Log Messages

To change the format of log messages, use the -o option. For more information, see the description of -o option in the official documentation.

root@raspberrypi4:/# journalctl -o json-pretty

__CURSOR=s=30a725fd9c054a66a0de5aee3b487afa;i=c4fe;b=6cf104d2c52d4397b4f52f53fa1
{
        "[[0;32m__MONOTONIC_TIMESTAMP[[0m" : "[[0;32m28192232542[[0m",
        "[[0;32m_SOURCE_REALTIME_TIMESTAMP[[0m" : "[[0;32m1623243329968117[[0m",
        "[[0;32m_UID[[0m" : "[[0;32m0[[0m",
        "[[0;32m_GID[[0m" : "[[0;32m0[[0m",
        "[[0;32mCODE_LINE[[0m" : "[[0;32m5805[[0m",
        "[[0;32m_TRANSPORT[[0m" : "[[0;32mjournal[[0m",
        "[[0;32m_SYSTEMD_CGROUP[[0m" : "[[0;32m/init.scope[[0m",
        "[[0;32mSYSLOG_FACILITY[[0m" : "[[0;32m3[[0m",
        "[[0;32mEXIT_STATUS[[0m" : "[[0;32m1[[0m",
        "[[0;32mCOMMAND[[0m" : "[[0;32mExecStart[[0m",
        "[[0;32mMESSAGE_ID[[0m" : "[[0;32m98e322203f7a4ed290d09fe03c09fe15[[0m",

        ...
}

...

Follow Logs

journalctl can print log messages to the console as they are added, similar to the Linux tail command. To do this, add the -f option.

root@raspberrypi4:/# journalctl -f

This can be also used with the -u option to filter the messages from a specific unit.

root@raspberrypi4:/# journalctl -u sam.service -f

Read from Specific journald Log Files

To read logs on one or more journald log files with a specific naming pattern, use the --file option with GLOB as an argument. If specified, journalctl will operate on the journal files matching GLOB instead of the default runtime and system journal paths.

root@raspberrypi4:/# journalctl --file /path/to/file/system.journal

Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 and sample code is licensed under the Apache License 2.0.

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