Get VM information with queries

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Now that a VM has been created, detailed information about it can be retrieved. The common command for getting information from a resource is show.

az vm show --name $vmName --resource-group $resourceGroup

A Virtual Machine has many properties that can be difficult to parse visually. The returned JSON contains information on authentication, network interface storage, and more. Most importantly, it contains the Azure object IDs for resources that the VM is connected to. Object IDs allow accessing these resources directly to get more information about the VM's configuration and capabilities.

In order to extract the object ID, the --query argument is used. Queries are written in the JMESPath query languageStart with getting the network interface controller (NIC) object ID.

az vm show --name $vmName \
  --resource-group $resourceGroup \
  --query 'networkProfile.networkInterfaces[].id' \
  --output tsv

There's a lot going on here, just by adding the query. Each part of it references a key in the output JSON, or is a JMESPath operator.

  • networkProfile is a key of the top-level JSON, which has networkInterfaces as a subkey. If a JSON value is a dictionary, its keys are referenced from the parent key with the . operator.
  • The networkInterfaces value is an array, so it's flattened with the [] operator. This operator runs the remainder of the query on each array element. In this case, it gets the id value of every array element.

The output format tsv (tab-separated values) is guaranteed to only include the result data and whitespace consisting of tabs and newlines. Since the returned value is a single bare string, it's safe to assign directly to a shell variable.

For more information about querying Azure CLI output, see How to query Azure CLI command output using a JMESPath query

Go ahead and assign the NIC object ID to a shell variable now.

nicId=$(az vm show \
  -n $vmName \
  -g $resourceGroup \
  --query 'networkProfile.networkInterfaces[].id' \
  -o tsv)

This example also demonstrates the use of short arguments. You may use -g instead of --resource-group, -n instead of --name, and -o instead of --output.