On Thu, 2009-12-17 at 15:34 -0500, Chuck Lever wrote:
> On Dec 17, 2009, at 3:27 PM, Trond Myklebust wrote:
> > One alternative might be to just record the kernel's random boot_id in
> > the pid file. That gets regenerated on each boot, so should be unique.
>
> Where do you get it in user space? Is it available on earlier
> kernels? ("should be unique" -- I hope it doesn't have the same
> problem we had with XID replay on diskless systems).
You can access it from userland as the 'kernel.random.boot_id' sysctl.
It is available on 2.4 kernels and newer.
It is based on the kernel random number generator, so should be
reasonably unique.
> Fwiw, I tried using the boot time stamp at one point, but
> unfortunately that's adjusted by the ntp offset, so it can take
> different values over time. It was difficult to compare it to a time
> stamp recorded in a file.
Agreed. You can't rely on time stamps.
Trond
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