[dns-operations] Multi-master setups

[Phil Regnauld]

Phil Pennock (dnsop+phil) writes:
> 
> You can rsync to a new directory, using --link-dest to reference the
> existing content.  This way you only transfer the changes, but build up
> an entirely new directory hierarchy, hard-linking in the unchanged files
> from the serving area.

	Very, very useful - and allows for generations of snapshots,
	only using inodes for directories. Rename previous dir, rsync
	into a new dir with --link-dest pointing to the old dir, etc.

> So you might have /var/dns/current where "current" is a symlink to a
> directory named, say, "20130520T1720.$somepid"; you use --link-dest to
> reference the existing current during sync; to be really cautious, you
> pick some other recent dirs and --link-dest multiple times, so that if
> you *do* have something go horribly wrong, the recovery still doesn't
> have to do a lot of transfers but can recover quickly, using existing
> content.

	Yep.