Messages in this thread | | | Date | Thu, 19 Jan 2006 21:18:57 +0100 | From | Willy Tarreau <> | Subject | Re: 2.4.x kernel uptime counter problem |
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On Thu, Jan 19, 2006 at 09:29:51AM +0000, Nick wrote: > On 1/19/06, Rumi Szabolcs <rumi_ml@rtfm.hu> wrote: > > Hello! > > > > I've got a Linux system running the 2.4.26 kernel which was about > > to pass the 500 day mark these days and now suddenly what I see is > > that the uptime counter has reset: > > > > $ uname -a && w && cat /proc/uptime && last -1 reboot > > Linux quasar 2.4.26 #3 SMP Tue Sep 7 09:22:08 CEST 2004 i686 Intel(R) Pentium(R) 4 CPU 2.60GHz GenuineIntel GNU/Linux > > 09:38:08 up 1 day, 12:49, 5 users, load average: 0.00, 0.00, 0.00 > > USER TTY LOGIN@ IDLE JCPU PCPU WHAT > > rumi pty/s0 08:53 0.00s 0.04s 0.02s screen -r > > rumi ttyp1 10Sep04 31:58 9:12 9:12 epic > > rumi ttyp3 Tue12 44:33m 0.01s 0.01s -/bin/bash > > rumi ttyp2 13Feb05 8days 0.11s 0.11s -/bin/bash > > rumi ttypc 11Dec05 0.00s 0.12s 0.11s -/bin/bash > > 132596.51 39801752.60 > > reboot system boot 2.4.26 Tue Sep 7 18:47 (498+15:50) > > > > From the above it can be seen that the system is running continuously > > and wasn't rebooted 36 hours ago as the uptime counter would suggest. > > > > Is this a known bug? > > > It's not a bug - it is a feature. uptime rolls over after 497 days. > > [sic] > It computes the result of the "uptime" based on the internal "jiffies" > counter, which counts the time since boot, in units of 10 > milliseconds. > This is typecast as an "unsigned long" - on the Intel boxes, that's an > unsigned 32-bit number. > Well, it turns out that in a 32-bit number, you can store 497.1 days > before the number wraps. > > > You can use: > last -xf /var/run/utmp runlevel > > to get true uptime in this instance. > > Nick
I would add that if you need to get valid outputs after such an uptime, you can apply the vhz-j64 patch available at Robert Love's (RML) on kernel.org.
Regards, Willy
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