EC2 Cloudformation configuation doesn't account for EBS volume?

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1

I’ve got a Cloudformation stack that provisions webserver using the following:

  WebServer:
    Type: AWS::EC2::Instance
    Properties:
      KeyName: !Ref KeyName
      ImageId: ami-030296bb256764655
      InstanceType: t3.medium
      SecurityGroupIds:
        - !Ref WebServerSecurityGroup1
      SubnetId: !Ref PublicSubnet2
      BlockDeviceMappings:
        - DeviceName: /dev/sda1
          Ebs:
            VolumeSize: 120
      UserData:
        Fn::Base64:
          Fn::Sub: |
            { 
              imports = [ <nixpkgs/nixos/modules/virtualisation/amazon-image.nix> ];
              ec2.hvm = true;
              swapDevices = [{
                device = "/var/swap";
                size = 1024 * 16;
              }];
              nix = {
                gc = {
                automatic = true;
                dates = "05:15";
                };
                binaryCaches = [
                  "https://cache.nixos.org"
                  "http://hydra.foo.org:5000"
                ];
                binaryCachePublicKeys = [ "foo" ];
              };
            }
      Tags:
        - Key: Name
          Value: !Sub "foo-${Stage}"

Much to my surprise, when I ssh as root to this machine, df -h reports:

# df -h
Filesystem                Size  Used Avail Use% Mounted on
devtmpfs                  195M     0  195M   0% /dev
tmpfs                     1.9G     0  1.9G   0% /dev/shm
tmpfs                     971M  3.4M  968M   1% /run
tmpfs                     1.9G  360K  1.9G   1% /run/wrappers
/dev/disk/by-label/nixos  3.0G  3.0G     0 100% /
tmpfs                     1.9G     0  1.9G   0% /sys/fs/cgroup
tmpfs                     389M     0  389M   0% /run/user/0

What’s the correct way to provision this such that nix uses the the /dev/sda1 devince with 120G?

2

Aye! The root volume on EC2 instances are /dev/xvda, not sda1! Changing DeviceName to /dev/xvda fixes it.