Check dmesg


Kernel messages are written to a preallocated ring buffer known as the dmesg buffer. A ring buffer is a sequential memory structure, where data overflow starts at the top of the buffer. Over time, newer messages fill the buffer and overwrite original messages, but the buffer never grows in size. This plugin 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


Compiled for



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.

  -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_c_preinit_dcmds: Firmware: BCM4345/6', '
                        brcmfmac: brcmf_fw_alloc_request: using
                        brcm/brcmfmac43455-sdio for chip BCM4345/6', ' CIFS
                        VFS: Free previous auth_key.response = ', ' cpufreq:
                        __cpufreq_add_dev: ->get() failed', ' EFI MOKvar
                        config table is not in EFI runtime memory', ' ERST:
                        Failed to get Error Log Address Range.', ' i8042: No
                        controller found', ' Ignoring unsafe software power
                        cap!', ' integrity: Problem loading X.509 certificate
                        -126', ' ioctl error in smb2_get_dfs_refer rc=-5', '
                        kvm_set_msr_common: MSR_IA32_DEBUGCTLMSR ', ' mokvar:
                        EFI MOKvar config table is not in EFI runtime memory',
                        ' No Caching mode page found', ' SMBus base address
                        uninitialized - upgrade BIOS or use ', ' SMBus Host
                        Controller not enabled!', ' tsc: Fast TSC calibration
                        failed', ' unhandled rdmsr: ', ' unhandled wrmsr: ', '
                        vcpu0 disabled perfctr wrmsr', ' Warning: Deprecated
                        Driver is detected', ' Warning: Unmaintained driver is
  --severity {warn,crit}
                        Severity for alerting. 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