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pmda persistent indom cache access issues

To: PCP Mailing List <pcp@xxxxxxxxxxx>
Subject: pmda persistent indom cache access issues
From: Ken McDonell <kenj@xxxxxxxxxxxxxxxx>
Date: Thu, 02 May 2013 11:02:40 +1000
Delivered-to: pcp@xxxxxxxxxxx
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Anyone else noticed that since pmcd and pmdas may no longer run as root the 
persistent indom cache in /var/lib/pcp/config/pmda cannot be written by 
some/all pmdas?

I don't know why this has changed recently, but I have a whole bunch of QA 
failures of the form

pmda cache persistance failed: Permission denied at 
/var/lib/pcp/pmdas/simple/pmdasimple.pl line 127

that started passing when I changed /var/lib/pcp/config/pmda to mode 1777 and 
removed the old 253.1 file that was owned by root and I see files in there 
being owned by the user "pcp" now.

The Linux pmda was silently unable to write its indom cache files apparently 
... when I removed the old 60.* ones owned by root, and restarted pmcd, new 
ones appeared owned by "pcp".

So changing the mode is only part of the fix ... we need to consider what to do 
about migration/upgrade issues where old files owned by root may be left around.

And any pmda run with a sudo dbpmda in qa will break all of this nicely, so 
there may be qa knock-ons.

Thoughts?  Ideas?

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