[tinus_hn]

Yes. There’s software, like dhcp clients, that has claimed the right to automatically edit this without leaving a trace. It’s really hard to turn off, it’s easier to just ban this behavior categorically, if your use case is not the one in which this behavior is useful.

[octoberfranklin]

This. I find it inexcusable that the Debian udhcpc package still does not provide any configuration option to inhibit it from overwriting /etc/resolv.conf.

The only option is to replace the "execute this when DHCP reply is recieved" script, which is not a simple script at all. And then you're stuck three-way-merging your changes to that script with every security update.