On Wed, Jun 22, 2005 at 11:38:02AM +0100, Ian Stokes-Rees wrote:
> Peter Gronbech wrote:
> >We use a combination of yum (to load updated rpms), yumit to advise us
> >on the patch status, and copy of an ssh key in
> [snip]
> >I can then spot that systems need patching with yumit, check what is
> >required (ie which oatches are missing, again with yumit) and the type
> >ont2nodes yum -y update
> >I'm sure there are many other solutions to this problem but this works
> >for me.
>
> Wow, that just made me realise "yet another complication of grid
> computing". Pete's system sounds excellent. Very simple to manage. I
> would imagine there could be big implications for running jobs, though,
> if the software they are using is changing under their feet.
>
> Are there risks that this might throw off software execution? I
> certainly imagine it might. We (LHCb) do a bunch of software version
> checks at the start of execution (and not just for LHCb/Physics
> software). Weird failures are one thing, but failures are probably
> better than producing bad results *without* any errors or output
> inconsistencies due to changes in software between two steps of a job.
>
> What happens if a library is updated? I don't know enough about how
> link-resolution and inodes work to understand whether dynamic libraries
> are all "referenced" at the start of execution, so the OS holds inode
> references to the old library, even if the physical file changes later
> (but still during execution of some process which is referencing it).
System library updates won't cause any problems. The new version is always
binary compatible (as long as you don't jump to RHEL4 from RHEL3 for example).
LCG libraries on the other hand might not work like that :(
In any case if your executable is running all libraries that is using are already
mmapped in it's memory space (cat /proc/self/maps) and the system will keep them
around until the job finishes, any dlopens will get the new libraries of course
so you might have a problem there.
Kostas
I upgraded my desktop online from FC3 to FC4 last week and i didn't even logged out
for a few days without any problems :)
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