[rrd-users] Locking *read* (copy/backup) of RRD files?

bern Jochen.Bern at LINworks.de
Mon Oct 25 19:31:50 CEST 2010

Hello everyone,

I'd like to be able to make backups of RRD files while Nagios is happily
writing data to them. From what I've read so far,

-- a plain "cp" (or, for that matter, rsync) will occasionally produce
inconsistent files (see, e.g.,
http://oss.oetiker.ch/rrdtool/forum.en.html#nabble-td5410407 );

-- rrddump gives me even better (arch-independent) exports, but still does
*not* call rrd_lock() to ensure consistency;

-- rrdresize does the locking, but insists on making *some* change to the
RRD structure (adding or removing at least one line - easy to hack to permit
==0, though);

-- taking boilerplate "plain file copy" C code and peppering it with the
necessary fcntl()s myself would work, but also makes for a nasty surprise
*if* rrdtool should ever change its preferred file locking method(s); and

-- there's no COPY/BACKUP/EXPORT command or somesuch built into rrdcached

(Alas, I'm not able to add snapshot capabilities to the underlying
filesystem right away.)

Is there a preferred, or even official, method to back up RRD files so that
they won't turn out to be damaged (short of disk or filesystem failures, of

Kind regards,
J. Bern
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