Is /etc/resolv.conf changed every time the DHCP lease changes

dnslaunchdNetworkwifi

I'd like to fire an event via launchd whenever my DHCP lease changes the IP on my WiFi interface. My question is similar to what's being asked in this question, which makes me thing I can watch /etc/resolv.conf for changes via a launchd agent.

I differ in my need in that I'd like to fire the event every time the IP changes on an interface, not just when the interface comes up. For the curious, yes, I'm looking to do a simple dynamic DNS updater.

Best Answer

You could write a launchd that monitors the file path of:

/private/var/db/dhcpclient/leases/

If you looking for DHCP changes to an interface.

That db holds all the different interfaces and dhcp changes on them. Something similar to monitoring that file with a launchd here.

Related Solutions

How to release and renew the DHCP lease from Terminal

This can also be achieved with the following two commands :

sudo ipconfig set en0 BOOTP
sudo ipconfig set en0 DHCP

You can alias the two together in your bash profile:

alias renew="sudo ipconfig set en0 BOOTP && sudo ipconfig set en0 DHCP"

So then you just have one command called renew that will release and renew your DHCP.

MacOS – nslookup works with /etc/resolv.conf, ping and ssh don’t

Well, did you read the comments at the top of /etc/resolv.conf?

# Mac OS X Notice
#
# This file is not used by the host name and address resolution
# or the DNS query routing mechanisms used by most processes on
# this Mac OS X system.

The correct solution is to add the search domains via the Network panel in System Preferences as described here.

Best Answer

Related Solutions

How to release and renew the DHCP lease from Terminal

MacOS – nslookup works with /etc/resolv.conf, ping and ssh don’t

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