Changing DNS Settings on ESXi Hosts

Changing DNS Settings on ESXi Hosts is an article that shows an automated approach to changing the DNS configurations on all connected ESXi hosts under the same vCenter Server, using a Python script.

The idea is to use a Linux CentOS 9 as a script server. We’ll execute a Python script from this server to connect to each ESXi host and upgrade the VMware Tools.

1- Install CentOS 9 (without GUI) – We have tested it with CentOS 9, but feel free to install a different Linux flavor and adjust the script to run on it.

2- Access it by SSH with root rights and install Python:

curl -O https://raw.githubusercontent.com/danchiacchio/scripts/refs/heads/main/sh_PythonInstall/install-python.sh

chmod +x install-python.sh

./install-python.sh

Grab a coffee and wait for a while. The automated Python install takes a while to complete! ☕

3- Creating a working directory (something such as /root/scripts/py_vESXiDNS) – you can choose the directory name:

mkdir -p /root/scripts/py_vESXiDNS

4- Go to the working directory and download the Python script “py_vESXiDNS.py“:

cd /root/scripts/py_vESXiDNS

curl -O https://raw.githubusercontent.com/danchiacchio/scripts/refs/heads/main/py_vESXiDNS/py_vESXiDNS.py

pip install pyvmomi paramiko

5- Run the Python script:

chmod 700 py_vESXiDNS.py

python py_vESXiDNS.py

Rechecking the DNS config after changing the DNS Servers and DNS domain name:

In the following picture, we run the nslookup inside each ESXi host. The command failed because we’re using an unreachable DNS server:

After fixing it (changed to a working DNS server):

That’s it 🙂

Note: So, I tested it several times in a lab environment, and it worked as expected. However, be careful when executing it in a production environment. We’ll not be responsible for downtime or weird behavior in your environment!