I'm trying to configure some virtual hosts and I'm quite confused as to when this file is loaded.
At what point is /private/etc/hosts loaded? When logging in? At every DNS call? When Mac OS restarts?
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2 Answers
The hosts(5) manual page provides some insight into how /etc/hosts is used.
The file is used by mDNSResponder and, given your question, I suspect you want to see edits to /etc/hosts reflected in your DNS look-ups.
After each edit of /etc/hosts reset the mDNSResponder cache using this Apple technical note, OS X: How to reset the DNS cache:
sudo dscacheutil -flushcache The note explains when you might need to do this:
When you might want to do this
OS X keeps a local cache of resolved DNS queries for a time defined by the DNS server, but sometimes it may be necessary to reset the cache immediately and re-query a DNS server. For example, you might do this after an entry on the server is changed or a new entry is added.
Usually changes to /etc/hosts are updated automatically within a few seconds, and I haven't needed to reset the DNS cache manually.
If you try to run sudo opensnoop|grep /etc/hosts and edit /etc/hosts, /etc/hosts is read by mDNSResponder almost immediately after you save it.
- 2I suspect in later versions of OS X, Apple started actively watching the
hostsfile for changes using the kqueue mechanism.Graham Miln– Graham Miln2014-02-17 07:53:37 +00:00Commented Feb 17, 2014 at 7:53