MCELOG(8) Linux's Administrator's Manual MCELOG(8)NAMEmcelog - Print machine check log from x86-64 kernel.
SYNOPSISmcelog [--syslog] [--k8|--p4|--generic] [--ignorenodev] [--dmi] [--fil‐
ter] [device]
mcelog [--k8|--p4|--generic] --ascii
DESCRIPTION
Linux x86-64 kernels since 2.6.4 don't print recoverable machine check
errors to the kernel log anymore. Instead they are saved into a special
kernel buffer accessible using /dev/mcelog. mcelog reads /dev/mcelog
and prints the stored machine check records to stdout. Then the stored
machine check records in the kernel buffer are deleted.
When the --syslog option is specified redirect output to system log.
When --k8 is specified assume the events are for a AMD Opteron or
Athlon 64 or Athlon FX CPU. With --p4 is specified assume the events
are for a Intel Pentium 4 or Intel Xeon. When --generic all the fields
are dumped without CPU specific decoding. Default is to decode for the
CPU mcelog is running on.
With the --dmi option mcelog will look up the addresses reported in
machine checks in the SMBIOS/DMI tables of the BIOS. This can some‐
times tell you which DIMM or memory controller has developed a problem.
More often the information reported by the BIOS is either subtly or
obviously wrong or useless. This option requires that mcelog has read
access to /dev/mem (normally requires root) and runs on the same
machine in the same hardware configuration as when the machine check
event happened.
When --ignorenodev is specified then mcelog will exit silently when the
device cannot be opened. This is useful in virtualized environment with
limited devices.
When --filter is specified mcelog will filter out known broken machine
check events.
When a device is specified the machine check logs are read from device
instead of the default /dev/mcelog.
With the --ascii option mcelog decodes a fatal machine check panic gen‐
erated by the kernel ("CPU n: Machine Check Exception ...") in ASCII
from stdout. This is useful to make sense of the hexadecimal numbers
in there. Note that when the panic comes from a different machine than
where mcelog is running on you might need to specify the correct archi‐
tecture ( --k8 or --p4 ).
NOTES
The kernel prefers old messages over new. If the log buffer overflows
only old ones will be kept.
The exact output depends on the CPU.
This program should be run regularly from cron to collect machine check
events.
SMBIOS/DMI output is very unreliable and often wrong. Not Linux's fault
- complain to your motherboard vendor.
FILES
/dev/mcelog (char 10, minor 227)
SEE ALSO
AMD x86-64 architecture programmer's manual, Volume 2, System program‐
ming
IA32 Intel Architecture Software developer's manual, Volume 3, System
programming guide
Datasheet of your CPU.
SuSE Labs Mar 2004 MCELOG(8)
