If you’ve used Linux on Azure for any length of time you’ll find an annoying search domain that Azure DHCP appends to your resolv.conf.
Here’s a copy of my resolv.conf as an example.
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 192.168.10.11
nameserver 192.168.10.12
search reddog.microsoft.com
Microsoft does this by default even if you have your own internal name servers since the DHCP process within a VNET is handled by Azure.
To get rid of this annoyance you can edit your /etc/dhcp/dhclient.conf and add the following one liner:
supersede domain-name "dky.io";
After that you can refresh DHCP with:
sudo dhclient -v
Once done check your /etc/resolv.conf to find the search domain reddog.* to be replaced with your domain above.