title: GCP create an instance template from an existing VM
body: <p>I am attempting to create an instance template from an existing powered off VM.  The VM is a pretty basic Centos Linux box.  After a bit of googling the problem I came up with the following but I can't figure out how to format the disk device name.  There are not a lot of examples out there I can find.  Thanks in advance for any light you can shed on the subject.</p>
  <pre><code>$gcloud compute instance-templates create plainid-pocv12-cent8-autostart --source-instance ajm-centos8 --configure-disk=device-name=/dev/sda,instantiate-from=source-image,auto-delete=true
  
  ERROR: (gcloud.compute.instance-templates.create) Could not fetch resource:
   - Invalid value for field 'resource.sourceInstanceParams.diskConfigs[0].deviceName': '/dev/sda'. Device name specified in disk instantiation config not found in source instance: '/dev/sda'.
  
  </code></pre>
  <p>Per the suggestions below, I ran the describe.  Looks like the device name is also 'ajm-centos8'</p>
  <pre><code>$gcloud compute instances describe ajm-centos8
  canIpForward: false
  confidentialInstanceConfig:
    enableConfidentialCompute: false
  cpuPlatform: Intel Haswell
  creationTimestamp: '2020-10-05T06:04:50.611-07:00'
  deletionProtection: false
  description: ''
  disks:
  - autoDelete: true
    boot: true
    deviceName: ajm-centos8
    diskSizeGb: '30'
    guestOsFeatures:
    - type: UEFI_COMPATIBLE
    - type: VIRTIO_SCSI_MULTIQUEUE
    - type: SEV_CAPABLE
    index: 0
    interface: SCSI
    kind: compute#attachedDisk
    licenses:
    - https://www.googleapis.com/compute/v1/projects/centos-cloud/global/licenses/centos-8
    mode: READ_WRITE
    source: https://www.googleapis.com/compute/v1/projects/plainid-presales/zones/us-east1-b/disks/ajm-centos8
    type: PERSISTENT
  </code></pre>
  <p>So now I am running the following command.  It creates a template yay!  However, the new template does not have any of the software I installed on the original VM installed on it.</p>
  <pre><code>$gcloud compute instance-templates create plainid-pocv12-cent8-autostart --source-instance ajm-centos8 --configure-disk=device-name=ajm-centos8,instantiate-from=source-image,auto-delete=true
  Created [https://www.googleapis.com/compute/v1/projects/plainid-presales/global/instanceTemplates/plainid-pocv12-cent8-autostart].
  NAME                            MACHINE_TYPE                   PREEMPTIBLE  CREATION_TIMESTAMP
  plainid-pocv12-cent8-autostart  custom (e2, 2 vCPU, 6.00 GiB)               2020-10-09T13:55:02.563-07:00
  </code></pre>