Cloud formation - Device index cannot be empty - json

Question

I have been trying to get two instances to join a domain and one be the dc. The code is from one of the templates however it doesnt let me run it with my modification.
I am getting the error DeviceIndex cannot be empty when the DC01 instance initiates.
This is the code for DC01
{
"Resources": {
"DC1": {
"Type": "AWS::EC2::Instance",
"Properties": {
"BlockDeviceMappings": [
{
"DeviceName": "/dev/sda1",
"Ebs": {
"VolumeSize": "40"
}
}
],
"ImageId": {
"Ref": "BaseAmiId"
},
"InstanceType": "t2.micro",
"KeyName": {
"Ref": "KeyName"
},
"NetworkInterfaces": [
{
"AssociatePublicIpAddress": "false",
"DeleteOnTermination": "true",
"DeviceIndex": "0",
"GroupSet": [
{
"Ref": "PrivateSecurityGroup"
}
],
"PrivateIpAddress": "10.1.3.100"
},
{
"SubnetId": {
"Ref": "PrivateSubnetAZ1"
}
}
],
"Tags": [
{
"Key": "Name",
"Value": "DC1"
}
],
"UserData": {
"Fn::Base64": {
"Fn::Join": [
"",
[
"<script>\n",
"cfn-init.exe -v -c config -s ",
{
"Ref": "AWS::StackId"
},
" -r DC1",
" --region ",
{
"Ref": "AWS::Region"
},
"\n",
"</script>\n"
]
]
}
}
}
}
}
}

Answer 1

You have created json formats in Network-Interface. So, it is considering the second one. Please try the below code snippet.
{
"Resources": {
"DC1": {
"Type": "AWS::EC2::Instance",
"Properties": {
"BlockDeviceMappings": [
{
"DeviceName": "/dev/sda1",
"Ebs": {
"VolumeSize": "40"
}
}
],
"ImageId": {
"Ref": "BaseAmiId"
},
"InstanceType": "t2.micro",
"KeyName": {
"Ref": "KeyName"
},
"NetworkInterfaces": [
{
"SubnetId": {
"Ref": "PrivateSubnetAZ1"
},
"AssociatePublicIpAddress": "false",
"DeleteOnTermination": "true",
"DeviceIndex": "0",
"GroupSet": [
{
"Ref": "PrivateSecurityGroup"
}
],
"PrivateIpAddress": "10.1.3.100"
}
],
"Tags": [
{
"Key": "Name",
"Value": "DC1"
}
],
"UserData": {
"Fn::Base64": {
"Fn::Join": [
"",
[
"<script>\n",
"cfn-init.exe -v -c config -s ",
{
"Ref": "AWS::StackId"
},
" -r DC1",
" --region ",
{
"Ref": "AWS::Region"
},
"\n",
"</script>\n"
]
]
}
}
}
}
}
}
It will resolve the issue