Azure: Convert ARM templates to Bicep and Bicep to ARM

 If you have some old ARM templates in your environment, it can make sense to update them to Bicep to benefit from newer features and simplified syntax.

There are some general guidelines on the Microsoft site here.

To convert the ARM templates to Bicep, you can use the Bicep tools. Bicep tools can be installed as an AZ CLI version, install info (cmd structure is: az bicep decompile) or as a Bicep CLI version, install info (where the cmd is e.g.: bicep decompile).

To create a Bicep file from an ARM template, use the following command:

bicep decompile <ARM template filename>

or

az bicep decompile --file <ARM template filename>

This will create a Bicep file and place it in the same folder as where the ARM template is located.

You can also convert from Bicep to ARM by using the bicep build command. This can be useful if you want to see what the Bicep is translated into before it is deployed. Note that this command does not account for a parameters file (if you have that), only the Bicep file itself.

bicep build <Bicep file name>

or

az bicep build --file <Bicep file name>

When you have converted a template, it is a good idea to run the deployment with the what-if option to check that nothing changes compared to what is already deployed. See here for more on using what-if.

Note that LLMs have gotten better at ARM templates and Bicep lately. Now, it is quite efficient at suggesting improvements and sanity checking code. This could be for example if you have repetitive code that can be optimized with a copy loop or if you want to optimize parameter naming with concat to construct names.