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RE: ctime vs checksum in copies


From: Nielsen, Steve
Subject: RE: ctime vs checksum in copies
Date: Wed, 30 Nov 2005 15:59:18 -0500

Of source keep in mind the template will be transformed to the
production copy in the temp area every time cfengine runs on the local
box.  But (at least IMO) is not a big deal in the grand scheme of
things.

Steve

-----Original Message-----
From: Paul Krizak [mailto:address@hidden 
Sent: Wednesday, November 30, 2005 2:56 PM
To: Nielsen, Steve
Cc: address@hidden
Subject: Re: ctime vs checksum in copies

Ah, I see now...groovy.  I wasn't thinking far enough out of the box to 
realize you could keep a copy of the template *on* the client :-)

Thanks for the tip!

Paul Krizak                         5900 E. Ben White Blvd. MS 625
Advanced Micro Devices              Austin, TX  78741
Linux/Unix Systems Engineering      Phone: (512) 602-8775
Microprocessor Solutions Sector


Nielsen, Steve wrote:
> If you copy the template over using a checksum to the temp area it
would
> only be copied when the template on the master changed. That is how I
> currently do it.
> 
> Steve
> 
> -----Original Message-----
> From: Paul Krizak [mailto:address@hidden 
> Sent: Wednesday, November 30, 2005 2:20 PM
> To: Nielsen, Steve
> Cc: address@hidden
> Subject: Re: ctime vs checksum in copies
> 
> That's a fairly nifty approach, though it doesn't address the core
issue
> 
> of having to pull the master template off the server every time
cfagent 
> runs.  This isn't a big deal for 100-1000 hosts, but within 12 months 
> I'll be dealing with around 10,000 hosts, and doing something like 
> copying a 20k file once an hour (or even once a day) can do suprising 
> things to the network (like bring down filers)
> 
> I'm trying to plan ahead so that as our network grows, the amount of 
> network/CPU bandwidth required to keep the systems up to date stays 
> about the same or even goes down.
> 
> Paul Krizak                         5900 E. Ben White Blvd. MS 625
> Advanced Micro Devices              Austin, TX  78741
> Linux/Unix Systems Engineering      Phone: (512) 602-8775
> Microprocessor Solutions Sector
> 
> 
> Nielsen, Steve wrote:
> 
>>Generally I have this approach:
>>
>>- copy the template over to a "temp area" (i.e. /var/cfengine/temp)
>>- do file edits on the temporary copy
>>- compare the temp copy to the production and copy if changed (using
>>checksum).
>>
>>This has worked really well for me.
>>
>>Steve
>>
>>-----Original Message-----
>>From: address@hidden
>>[mailto:address@hidden On Behalf
>>Of Paul Krizak
>>Sent: Wednesday, November 30, 2005 1:14 PM
>>To: address@hidden
>>Subject: ctime vs checksum in copies
>>
>>I've got a question about what you guys think the best solution is in 
>>this situation.
>>
>>I've got some files that must be customized on a per-host basis, but
> 
> are
> 
>>based on a common "root" file.  My goal is to have the following
> 
> system:
> 
>>* When the system is first installed, or if the file on the system is 
>>wildly different than the master, a copy: statement pulls down a fresh
> 
> 
>>copy of the file, which an edifiles: stanza corrects for that specific
>>host.
>>
>>* Later, if the master file changes, the clients should "know" to pull
> 
> 
>>down a new copy of the file, and then perform the same editfiles:
> 
> stanza
> 
>>again.
>>
>>Using "checksum" for the copy statement doesn't really work, since
> 
> once 
> 
>>you make a change to the file using editfiles:, the checksums don't 
>>match and thus the file gets copied every time.  On the upside, you're
> 
> 
>>guaranteed to always have the correct version of the file on the
> 
> target 
> 
>>system.
>>
>>Using "ctime" for the copy statement *sounds* good, as the copy only 
>>happens when the "master" file updates on the server.  Where this
> 
> falls 
> 
>>flat, however, is on freshly installed systems, where the ctime of the
> 
> 
>>*incorrect*, freshly-installed file is *later* than the ctime of the 
>>"master" file.  In this situation, the "master" file is not copied
> 
> (and 
> 
>>I wouldn't expect it to).
>>
>>I've got several cases in my (very lengthy) cfengine config where I
> 
> run 
> 
>>into this type of issue.  For small files, I can put the entire
> 
> contents
> 
>>of the file into an editfiles: block and avoid using copy: at all.
> 
> This
> 
>>doesn't work for large files, however, as I don't want a cf.* file to 
>>have a 5,000-line config file in it with Append statements.
>>
>>For large files, I use checksum copies and just accept the fact that 
>>they will get copied every time cfagent runs.
>>
>>I'm looking to improve convergence in my config files...anybody else 
>>have clever workarounds for this problem?
>>
> 
> 
> 





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