Check dmesg


Checks the Kernel Ring Buffer for emerg, alert, crit and err messages using dmesg, and if the parameter --severity has not been ommitted, always returns CRIT if something is found.

Some very common dmesg messages are ignored, for example Assuming drive cache: write through (should be a debug message) or ioctl error in smb2_get_dfs_refer rc=-5 (a bug as stated in

Be aware that the reported timestamps could be inaccurate. The time source used for dmesg is not updated after system SUSPEND/RESUME. Timestamps are adjusted according to current delta between boottime and monotonic clocks, this works only for messages printed after last resume.

Fact Sheet

Check Plugin Download

Check Interval Recommendation

Once a minute

Can be called without parameters


Available for

Python 2, Python 3




usage: dmesg [-h] [-V] [--always-ok] [--ignore IGNORE]
             [--severity {warn,crit}] [--test TEST]

Checks dmesg for emerg, alert, crit and err messages. Executes `dmesg
--level=emerg,alert,crit,err --ctime `. If you fixed the issues (or just want
to clear them), use `dmesg --clear` to clear the Kernel Ring Buffer Messages.

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  --always-ok           Always returns OK.
  --ignore IGNORE       Ignore a kernel message (case-sensitive, repeating).
                        Default: [' Asking for cache data failed', ' Assuming
                        drive cache: write through', ' brcmfmac:
                        brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio
                        for chip BCM4345/6', ' brcmfmac:
                        brcmf_c_preinit_dcmds: Firmware: BCM4345/6', ' CIFS
                        VFS: Free previous auth_key.response = ', ' cpufreq:
                        __cpufreq_add_dev: ->get() failed', ' ERST: Failed to
                        get Error Log Address Range.', ' i8042: No controller
                        found', ' Ignoring unsafe software power cap!', '
                        ioctl error in smb2_get_dfs_refer rc=-5', '
                        kvm_set_msr_common: MSR_IA32_DEBUGCTLMSR ', ' No
                        Caching mode page found', ' SMBus Host Controller not
                        enabled!', ' tsc: Fast TSC calibration failed', '
                        unhandled rdmsr: ', ' unhandled wrmsr: ', ' vcpu0
                        disabled perfctr wrmsr']
  --severity {warn,crit}
                        Severity for alerting. One of "warn" or "crit".
                        Default: crit
  --test TEST           For unit tests. Needs "path-to-stdout-file,path-to-

Usage Examples

./dmesg --ignore ' unhandled wrmsr: ' --severity crit


5 errors in Kernel Ring Buffer.

[Mon May 31 18:27:14 2021] x86/cpu: SGX disabled by BIOS
[Sat Jun  5 18:49:50 2021] ACPI Error: Thread 2495397888 cannot release Mutex [ECMX] acquired by thread 1817575424 (20210105/exmutex-378)
[Sat Jun  5 18:49:50 2021] ACPI Error: Aborting method \_SB.PCI0.LPCB.ECDV._Q66 due to previous error (AE_AML_NOT_OWNER) (20210105/psparse-529)
[Tue Jun  8 18:54:41 2021] usb usb2-port1: Cannot enable. Maybe the USB cable is bad?
[Tue Jun  8 18:54:41 2021] usb usb2-port1: unable to enumerate USB device


  • CRIT or state given by --severity if any of emerg, alert, crit and err messages in dmesg are found.

Perfdata / Metrics

There is no perfdata.

Credits, License