Dmesg to real timestamp

Question

I would like convert my Centos 6.10 dmesg in real timestamp, how do I do this? I tried with -T but no luck. I have long entry like (1630230907.320:2)

score 0 · Answer 1 · answered Sep 25 '22 at 12:59

When neither the -T and/or --ctime flags to print human-readable timestamps are supported, you can manually convert the timestamp.

The timestamp in dmesg is the offset in seconds since last reboot so :

Determine the last reboot:

 [root@server ~]# last -n 1 reboot
 reboot   system boot  3.10.0-1160.76.1 Sat Aug 27 10:56 - 14:25 (29+03:28)

 wtmp begins Tue Nov  7 09:30:18 2017

For example my dmesg has an entry:

[2316645.206965] BIOS EDD facility v0.16 2004-Jun-25, 1 devices found

Then use date --date "[date of last-reboot] [timestamp] seconds to convert the timestamp:
```
date --date "Sat Aug 27 10:56 2316645.206965 seconds"

Fri Sep 23 06:27:37 CEST 2022
```

Which corresponds exactly with dmesg -T :

[Fri Sep 23 06:27:37 2022] BIOS EDD facility v0.16 2004-Jun-25, 1 devices found

I assume though that your time stamp is incorrect for some reason, 1630230907.32 seconds is over 50 years.

Reasons for incorrect timestamps are already given in the manual page man dmesg

   -T, --ctime
       Print human-readable timestamps.

       Be aware that the timestamp could be inaccurate! The time
       source used for the logs 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.

Suspend/resume events are not only something that only concerns laptop users, virtual systems may also experience them during live migration for example.

Dmesg to real timestamp

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