> On 13 May 2016, at 09:56, Hans Ginzel <h...@matfyz.cz> wrote: > > Does Postfix detect changes in /etc/resolv.conf to flush its dns caches etc, > please?
Changing /etc/resolv.conf has no impact on what DNS data an application or name server has cached. All that can do is tell an application which name servers to query or what domain names to append to the strings in the queries it sends. Applications generally just read /etc/resolv.conf exactly once when they start up. Most postfix processes tend to be short-lived. So they should pick up any changes to resolver configuration fairly soon (or even immediately) after /etc/resolv.conf has been updated. A “postfix reload” should be enough to ensure everything in the Postfix toolset makes use of the updated file. It’s probably unwise to change /etc/resolv.conf in day-to-day operations. That file should only ever need to be modified after a full OS install or a major redesign of someone’s network and DNS setup.
