Kernel Logs

The kmsg input plugin reads the Linux Kernel log buffer from the beginning. It gets every record and parses fields as priority, sequence, seconds, useconds, and message.

Configuration parameters

Key	Description	Default
Prio_Level	The log level to filter. The kernel log is dropped if its priority is more than prio_level. Allowed values are 0-8. 8 means all logs are saved.	8
Threaded	Indicates whether to run this input in its own thread.	false

Get started

To start getting the Linux Kernel messages, you can run the plugin from the command line or through the configuration file:

Command line

$ fluent-bit -i kmsg -t kernel -o stdout -m '*'

Which returns output similar to:

Fluent Bit v4.0.0
* Copyright (C) 2015-2025 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

______ _                  _    ______ _ _             ___  _____
|  ___| |                | |   | ___ (_) |           /   ||  _  |
| |_  | |_   _  ___ _ __ | |_  | |_/ /_| |_  __   __/ /| || |/' |
|  _| | | | | |/ _ \ '_ \| __| | ___ \ | __| \ \ / / /_| ||  /| |
| |   | | |_| |  __/ | | | |_  | |_/ / | |_   \ V /\___  |\ |_/ /
\_|   |_|\__,_|\___|_| |_|\__| \____/|_|\__|   \_/     |_(_)___/


[2025/06/30 16:12:06] [ info] [fluent bit] version=4.0.0, commit=3a91b155d6, pid=91577
[2025/06/30 16:12:06] [ info] [storage] ver=1.5.2, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2025/06/30 16:12:06] [ info] [simd    ] disabled
[2025/06/30 16:12:06] [ info] [cmetrics] version=0.9.9
[2025/06/30 16:12:06] [ info] [ctraces ] version=0.6.2
[2025/06/30 16:12:06] [ info] [input:health:health.0] initializing
[2025/06/30 16:12:06] [ info] [input:health:health.0] storage_strategy='memory' (memory only)
[2025/06/30 16:12:06] [ info] [sp] stream processor started
[2025/06/30 16:12:06] [ info] [output:stdout:stdout.0] worker #0 started
[0] kernel: [1463421823, {"priority"=>3, "sequence"=>1814, "sec"=>11706, "usec"=>732233, "msg"=>"ERROR @wl_cfg80211_get_station : Wrong Mac address, mac = 34:a8:4e:d3:40:ec profile =20:3a:07:9e:4a:ac"}]
[1] kernel: [1463421823, {"priority"=>3, "sequence"=>1815, "sec"=>11706, "usec"=>732300, "msg"=>"ERROR @wl_cfg80211_get_station : Wrong Mac address, mac = 34:a8:4e:d3:40:ec profile =20:3a:07:9e:4a:ac"}]
[2] kernel: [1463421829, {"priority"=>3, "sequence"=>1816, "sec"=>11712, "usec"=>729728, "msg"=>"ERROR @wl_cfg80211_get_station : Wrong Mac address, mac = 34:a8:4e:d3:40:ec profile =20:3a:07:9e:4a:ac"}]
[3] kernel: [1463421829, {"priority"=>3, "sequence"=>1817, "sec"=>11712, "usec"=>729802, "msg"=>"ERROR @wl_cfg80211_get_station : Wrong Mac address, mac = 34:a8:4e:d3:40:ec
...

As described previously, the plugin processed all messages that the Linux Kernel reported. The output has been truncated for clarification.

Configuration file

In your main configuration file append the following:

fluent-bit.yaml

pipeline:
    inputs:
        - name: kmsg
          tag: kernel

    outputs:
        - name: stdout
          match: '*'

fluent-bit.conf

[INPUT]
    Name   kmsg
    Tag    kernel

[OUTPUT]
    Name   stdout
    Match  *