[lug] Clock Skew

John Starkey jstarkey at ajstarkey.com
Thu Aug 10 20:30:38 MDT 2000

Ralph thanks for replying. I still have your message concering the JAVA
but I haven't been able to get back to that level. Sorry for the delay.

I think you pinpointed the problem. Here's what happened in detail. 

1) I started building a new ruleset for my firewall based on the ipmasq
howto. And as usual I digressed. What I was doing originally was to fix my
routing problem. Anyway, something I did lost my mods for eth0 and eth1.

2) I decided as my original message states that I'm tired of not knowing
the "innards" (to steal a slang from MD). So I went the Kernel compile
HOWTO. I did all the makes and a bzdisk. I got a little confused at that
point whether it was booting off the floppy. ( I did here the floppy
moving on boot, but hmmmm, I'm dumb :}) 

3) On a reboot I went into CMOS and checked to see what it has (new
machine). The clock was ahead by _only two hours_. Now I'm not sure since
I booted via disk image whether the mod dates had been changed. 

How often are they (the mod dates) changed (only on reboot, on an actual
root user modification of those files, or just on re-compiles? 

And is it only the kernel files?

I think this is why. I did the

find . | args touch

no should I recompile or should I leave it for now and only do a make

As a side-question/note. My eth0 is constantly blinking on the hub light.
Just before I noticed it I tried a ping to a name to check DNS. I wonder
if the ping is looping somehow (dumb question?? TTL doesn't change on hubs


Starkey :}

On Fri, 11 Aug 2000 rm at mamma.varadinet.de wrote:

> On Thu, Aug 10, 2000 at 09:12:57PM -0400, John Starkey wrote:
> > With all this crazy stuff going in my linux'ized life I got really tired
> > of feeling like I'm caught up in a black hole. Not knowing the bounds of
> > linux. 
> > 
> > Soooo. I'm doing my first kernel compile. I wanna step away from the world
> > of rpm's. 
> > 
> > I'm getting a warning right now that says "clock skew detected, build may
> > be incomplete." As is consistant with my usual bad timing (and leading to
> > confusion) I'm not sure whether this is related to the fact that I changed
> > the time in CMOS or it's pertaining to the internal clock speed.
> Definitely the first. You probably went back in time ...
> 'Make' (the tool that you use to build your kernel) looks at 
> all the source code files and compares their modification date
> with the modification date of the genereated program/kernel.
> This is done so that only those parts of a program get recompiled
> that depend on files that where changed after the last build.
> Now, if you have compiled a kernel (or unpacked the sources) and
> then reset your clock 'make' might see files with creation/modification
> times in the future. This is what it complains about. Be carefull:
> It's usually _not_ a good idea to leave a project like this. Some
> files might not get compiled correctly. The easiest fix is to
> change to the root of your sources and issue the following command:
>  find . | xargs touch
> This will set the modification date of all files to the current time.
> Of course now all files will be rebuild (after a 'make clean').
>  Ralf
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