NFS--mounted builddirs and detecting clock skew

[Harlan Stenn]

I have not put enough thought into the following.

A variety of problems can crop up if one is "doing things" in an
NFS-mounted filesystem and there is clock skew between the local machine
(NFS client box) and the machine that hosts the  actual filesystem (NFS
server box).

I am thinking there may be value in:

- a small script/executable that can detect a clock skew problem
- a configure test that sees if there is currently a clock skew problem
- a Makefile test that can detect a clock skew problem

The first item above could be used by the other two, and also by other
scripts that might care about this issue.

Background: I am being bitten by a clock skew problem in an environment
where it is sometimes a feature that clock skew exists.  When it exists,
however, there are still some operations that (properly) consider clock
skew to be a bug, and want to detect this condition, squawk, and
terminate.

If I am running a configure script and there is a clock skew problem, I
would want to know this ASAP beacuse if the clock skew is not
deliberate, I want to fix it Right Away.

Once I have run configure, my automake-based systems would benefit from
a rule in the Makefile that would let me know if there is clock skew.
Some of these systems are not running gmake.  And even if they are
running gmake, a rule that detects clock skew lets me take explicit
action.

I have some release-engineering scripts I use where it would also be
useful to know if there is a clock-skew problem.

Hmmm, I'm now thinking it might be useful to offer a small package along
these lines, where 'check-clock-skew' was implemented as C code, perl
(script and module), sh, and perhaps whatever else folks thought was
worth donating could be distributed.

So thoughts/ideas?

H