Published December 30th, 2002 by Jim O'Halloran
Linux Uptime Wraps Around
Noticed something odd with one of our servers over the Christmas break. Adelie was scheduled to reach 500 days uptime sometime on Thursday, but when I came in to the office today it was back to about 7 days. A little digging suggests that the linux kernel suffers from
“jiffies rollover” at around 497 days. This means that uptime counters reset to 0 after this 497 days, and this can also cause some funny process start times in a ps display. Seems this might be fixed in 2.4.18+ kernels or in the 2.5.x series.
One contributor to the thread linked above also had some wise words when interpreting uptime figures…
ps. long uptimes are cool, but you cant read too much into just the number; all software has bugs, but if you are lucky, and your working set doesnt hit them, any ‘real’ OS should stay up for arbitrarily long times. Machines that are heavily loaded, perform a wild variety of tasks, and still stay up forever are the most impressive, though.
European Unix Platform concludes that “the uptime returns to zero after 497 days, 2 hours, 27 minutes and 53 seconds.”
richlv Says
actually, it seems 2.4.24 also suffers from this problem.
from lastlog :
reboot system boot 2.4.24 Wed Mar 10 18:42 (545+22:31)
# uptime
18:13:31 up 48 days, 19:35
Sep 8th, 2005 at 12:42 am
Jima Says
Huh, I remember Googling and finding this psge eons ago when I “discovered” the rollover. Guess I forgot the details, because here I was, waiting for this machine to roll over before I decommissioned it, and I started to wonder, “wait, what time on day 497 does it roll?”
3:10pm up 497 days, 13:26, 22 users, load average: 0.08, 0.10, 0.09
Oops. Maybe the kernel was patched for this (either upstream or by my distribution, Aurora Linux), or maybe it’s because this is a 64-bit system (Sun Ultra 10), but…I don’t think it’s gonna roll.
It’s sad. I’m actually disappointed. I guess I’ll have to pick a new milestone to stop at. Maybe 500 days.
Jan 4th, 2006 at 6:47 am
Chris Says
This must have been fixed in 2.6.
# uname -r
2.6.14.3
# uptime
11:53:12 up 598 days, 23:14, 1 user, load average: 0.00, 0.00, 0.00
This is an IBM Netfinity 5600 with three power supplies and two hot spares on it’s raid array - it sits between LAN and WAN and filters with a transparent bridge (ebtables), also a samba file server. Just sits in a corner, doing it’s thing.
Sep 24th, 2007 at 2:25 am
jim Says
Chris, that’s what I love most about Linux. It just sits in the corner doing it’s thing, not bothering anyone.
Jim.
Sep 24th, 2007 at 6:45 am