LinuxSA Mailing list archives

  From: Alan Kennington <ak.linuxsa@topology.org>
  To  : LinuxSA <linuxsa@linuxsa.org.au>
  Date: Sun, 20 Apr 2003 14:51:19 +0930

uptime = 1 day, Grrrrr....

For the last 500 days, I've been taking pleasure in the fact that my
UPS protects me from the vagaries of the Adelaide electricity situation,
and I've been watching my graph at Netcraft UK
http://uptime.netcraft.com/up/graph/?mode_u=off&mode_w=on&site=www.topology.org
steadily climbing towards the 500 day mark.

Now I know that they say in their uptime notes
http://uptime.netcraft.com/up/accuracy.html#cycle

--------------------------------------------------------
The method that Netcraft uses to determine the uptime of i
a server is bounded by an upper limit of
497 days for some Operating Systems (see above). It is 
therefore not possible to see uptimes for
these systems that go beyond this upper limit. Although 
we could in theory attempt to compute the
true uptime for OS's with this upper limit by monitoring 
for restarts at the expected time, we prefer
not to do this as it can be inaccurate and error prone. 
--------------------------------------------------------

...but I understood this to mean that Netcraft's sneeky method of finding
out my server's uptime was deficient in some way.
(By the way, how _do_ they find out the uptime via TCP/IP?
It must be by TCP/IP port 80 because the server does no ICMP or UDP etc.,
and all ports apart from 80 are non-existent to the outside world.)

Somehow this note of theirs just didn't quite sink in:

--------------------------------------------------------
Additionally HP-UX, Linux, Solaris and recent releases of 
FreeBSD cycle back to zero after 497
days, exactly as if the machine had been rebooted at that 
precise point. Thus it is not possible to see a
HP-UX, Linux or Solaris system with an uptime measurement above 497 days. 
--------------------------------------------------------

I still thought it meant that the remote method of determining
uptime was lacking in some way, not the OS itself.

But now I check my uptime expecting to have gone over 500 days, and find this:

  2:38pm  up 1 day, 13:11, 32 users,  load average: 0.06, 0.03, 0.01        

Grrrr and double-Grrrr!

What is the point of a UPS if linux is just going to reset the uptime after
497 days?
Who's bright idea was it to make it impossible to boast a 500+ day uptime?
Now what's the point in me avoiding re-boots until the 2-year mark?
It will just show 233 days or something.
Who's going to believe me that 233 days is really 730 days?

So now people who look at my Netcraft UK graph will think I re-booted
after 497 days - just missing the 500.
This is not good for the reputation of linux stability!!
In this life, it is not enough to _be_ good. You have to be able to prove it!

Cheers, and Grrrr again,
Alan Kennington.

PS. Obviously now is a good time to rip in some more cheap RAM and a new kernel.
This finally answers for me the question: 
"How long should a linux system go between software and hardware upgrades."
Answer: 497 days.

================================================
    city: Adelaide, South Australia
  coords: 138.59 E, 34.88 S
timezone: UTC+1030 http://www.topology.org/site/timezone.html          

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