Migrating Linux virtual machines from VMware to STACKIT

The migration in order

1. 01

   Inventory the Linux estate

   Filter vInfo on the guest OS. The column OS according to the configuration file drives the end-of-support check, the VMware Tools column is the one to compare it with.

2. 02

   Choose image or rebuild per distribution

   Compare each guest with the STACKIT public image list. A listed distribution can be rebuilt from its public image. One that is not listed, or past support, needs an upgrade first or a custom image. The table below does this for the demo estate.

3. 03

   Consolidate snapshots and shut down cleanly

   Only the current state of a VM is migrated. The run notes this for every machine. Consolidate snapshots first and stop the guest in a controlled way before you copy the disk.

4. 04

   Convert the boot disk

   STACKIT accepts raw, qcow2 and iso. A tool such as qemu-img converts a VMDK, for example qemu-img convert -O qcow2 source.vmdk boot.qcow2. The engine does not run it.

5. 05

   Import the image

   Create the image through the IaaS API, upload the file to the upload address that comes back, and wait until the image state is AVAILABLE. Set boot mode on the image: BIOS or EFI is the architect's call, and the run lists it as an open setting.

6. 06

   Fill the variables and apply to a test project

   The draft asks for the image id and the machine type of each server and for the performance class of the volumes. Apply it to a test project first.

7. 07

   Copy the data of the extra disks

   Each further disk is an empty volume until you copy its data. StackToIT never moves data; choose the method per volume.

8. 08

   Adjust the guest, test, cut over

   Replace the VMware guest components, check the network names and mounts, then test and switch. The ledger below lists the checks.

Eight Linux hosts, three routes

Public image list as of November 2026, from the STACKIT operating system images page for Linux (read on 4 November 2026). STACKIT states that the images are not customized by STACKIT, that it licenses none of the Linux images except Red Hat Enterprise Linux, and that licensing of images you bring is yours.

End of support is checked, but only for some guests

A small RVTools export of eight Linux hosts written for this page and assessed by StackToIT on 4 November 2026. Left: the vInfo rows of old-cent7 and app-rhel7. Right: the findings recorded for them in assessment.json (finding identifiers left out).

VM,Powerstate,Template,CPUs,Memory,NICs,Disks,Provisioned MiB,In use MiB,Primary IP Address,Datacenter,Cluster,Host,Folder,Annotation,OS according to the configuration file,OS according to the VMware Tools,Firmware,Path,VM UUID
app-rhel7,poweredOn,False,4,8192,1,1,51200,25600,10.70.20.22,DC-Sued,CL-Linux,esx42,linux,,Red Hat Enterprise Linux 7 (64-bit),Red Hat Enterprise Linux Server 7.9,bios,[ds-linux-01] app-rhel7/app-rhel7.vmx,7003-dddd-0004
old-cent7,poweredOn,False,2,4096,1,1,40960,20480,10.70.20.23,DC-Sued,CL-Linux,esx43,linux,,CentOS 7 (64-bit),CentOS Linux 7 (Core),bios,[ds-linux-01] old-cent7/old-cent7.vmx,7003-dddd-0005

[
  {
    "id": "vm.old-cent7",
    "findings": [
      {
        "severity": "warning",
        "message": "The guest operating system is past its vendor's end of support. STACKIT public images will not cover it; migrate it as a custom image at your own risk or upgrade it first."
      },
      {
        "severity": "info",
        "message": "Not verifiable statically (snapshots not visible): The VM has snapshots; consolidate them before export — only the current state is migrated."
      },
      {
        "severity": "info",
        "message": "Legacy E1000 network adapter; the guest's network configuration must be checked after conversion."
      }
    ]
  },
  {
    "id": "vm.app-rhel7",
    "findings": [
      {
        "severity": "info",
        "message": "Not verifiable statically (snapshots not visible): The VM has snapshots; consolidate them before export — only the current state is migrated."
      }
    ]
  }
]

• CentOS 7 gets a warning

  The run says the guest is past its vendor's end of support and points to a custom image at your own risk or an upgrade first.

• RHEL 7 gets none

  In this run only the snapshot note appears for app-rhel7. The check did not flag RHEL 7, although its configuration-file column names the release, so the absence of a warning is not a statement that a guest is supported. Look every release up in the vendor lifecycle.

• E1000 adapter

  old-cent7 also uses an E1000 adapter. The run asks you to check the guest network configuration after conversion.

A database host with four disks

From the same run. Left: the four disks of db-deb12, one of them 2 TiB. Right: the server and the three volumes the engine drafted (the volume attachment blocks between them are left out).

VM,Disk,Capacity MiB,Raw,Disk Mode,Sharing mode,Thin,Controller,Shared Bus,VM UUID
db-deb12,Hard disk 1,51200,False,persistent,sharingNone,False,SCSI controller 0,noSharing,7003-dddd-0006
db-deb12,Hard disk 2,1048576,False,persistent,sharingNone,False,SCSI controller 1,noSharing,7003-dddd-0006
db-deb12,Hard disk 3,2097152,False,persistent,sharingNone,False,SCSI controller 2,noSharing,7003-dddd-0006
db-deb12,Hard disk 4,262144,False,persistent,sharingNone,False,SCSI controller 3,noSharing,7003-dddd-0006

resource "stackit_server" "vm_db_deb12" {
  project_id        = var.project_id
  name              = "db-deb12"
  machine_type      = var.vm_db_deb12_machine_type
  availability_zone = var.availability_zone
  boot_volume = {
    source_type = "image"
    source_id   = var.vm_db_deb12_image_id
    size        = 50
  }
  network_interfaces = [stackit_network_interface.vm_db_deb12_nic1.network_interface_id]
}

resource "stackit_volume" "vm_db_deb12_disk2" {
  project_id        = var.project_id
  name              = "db-deb12-disk2"
  availability_zone = var.availability_zone
  size              = 1024
  performance_class = var.vmware_volume_performance_class
}

resource "stackit_volume" "vm_db_deb12_disk3" {
  project_id        = var.project_id
  name              = "db-deb12-disk3"
  availability_zone = var.availability_zone
  size              = 2048
  performance_class = var.vmware_volume_performance_class
}

resource "stackit_volume" "vm_db_deb12_disk4" {
  project_id        = var.project_id
  name              = "db-deb12-disk4"
  availability_zone = var.availability_zone
  size              = 256
  performance_class = var.vmware_volume_performance_class
}

• Only the boot disk becomes an image

  The 50 GiB first disk is the boot volume. The 1, 2 and 0.25 TiB disks are volumes: no image import for them, but a data copy.

• Volume sizes follow the source

  1048576 MiB becomes 1024 GiB, 2097152 MiB becomes 2048 GiB. Confirm each size against what the data really needs.

• The image limit

  The STACKIT custom image how-to states a maximum image size of 70 GB. The page does not say whether that means file size or virtual size, so test it with your largest boot disk. sap-sles15 has an 80 GiB boot disk.

The image and the machine type are inputs

From the same run. Left: the vInfo row of sap-sles15. Right: the two variables the draft declares for its server.

VM,Powerstate,Template,CPUs,Memory,NICs,Disks,Provisioned MiB,In use MiB,Primary IP Address,Datacenter,Cluster,Host,Folder,Annotation,OS according to the configuration file,OS according to the VMware Tools,Firmware,Path,VM UUID
sap-sles15,poweredOn,False,8,65536,1,2,491520,245760,10.70.30.41,DC-Sued,CL-Linux,esx42,linux,,SUSE Linux Enterprise 15 (64-bit),SUSE Linux Enterprise Server 15 SP5,bios,[ds-linux-01] sap-sles15/sap-sles15.vmx,7003-dddd-0007

variable "vm_sap_sles15_image_id" {
  type        = string
  description = "STACKIT image converted from the boot disk of VM sap-sles15 (qcow2 or raw)."
}

variable "vm_sap_sles15_machine_type" {
  type        = string
  description = "STACKIT machine type replacing VM sap-sles15 (source 8 vCPU / 64 GiB). See https://docs.stackit.cloud/products/compute-engine/server/basics/machine-types/"
}

• Size is stated, type is chosen

  The description keeps the source size, 8 vCPU and 64 GiB. STACKIT machine types come in families with fixed CPU to memory ratios, such as 1:4 for general purpose and 1:8 for memory-optimized.

• Where this machine does not fit neatly

  db-deb12 has 8 vCPU and 48 GiB, which is neither 1:4 nor 1:8. Choose by what the database needs, not by the nearest label.

• Boot mode is not in the draft

  vInfo says efi or bios per machine. The run lists boot firmware as an open setting and says BIOS or EFI is a property of the uploaded image that the architect creates.

Guest checks before cutover (general practice)

• VMware guest components

  The run says VMware Tools, vmxnet3 and PVSCSI drivers are replaced by what the STACKIT image needs. Remove or disable the VMware tooling once the machine runs on STACKIT.

• Storage and network drivers in the boot image

  Before conversion check that the initial ramdisk can mount the root disk on virtual hardware that is not VMware. A missing driver there is a common reason a converted Linux guest does not boot.

• Mounts by UUID

  Replace device names such as /dev/sdb in fstab with UUIDs or labels. Attached volumes need not appear in the order of the old controllers.

• Network interface names

  Adapter names tied to the old hardware, for example in netplan, NetworkManager profiles or persistent rules, may no longer match. The interface keeps its IPv4 address from the export.

• Access and first boot

  STACKIT public images disable SSH password login by default and expect a stored key. For an imported disk, confirm which accounts and keys the guest already holds.

• Licences and agents

  Subscriptions, monitoring agents and backup agents tied to the old host need re-registration. Licensing of images you bring is your responsibility.

Decisions that stay with the architect

• Rebuild or convert

  Per machine. A rebuild gives a clean image on a listed distribution. A conversion keeps the exact system, including its history.

• Machine type

  Chosen from the STACKIT machine type page against measured load, not against the source size alone.

• Boot mode

  BIOS or EFI per image, matching the source firmware.

• Powered-off machines

  The draft writes no power state, and the run lists power-state as an open setting. Decide whether to migrate a powered-off VM at all.

• Availability zone

  The draft defaults to eu01-1. A person confirms the zone for each workload.

• Volume performance class

  One variable for the whole estate, so storage is decided in one place.

Questions about Linux VMs

Sources

• STACKIT docs: Operating system images (Linux)
• STACKIT docs: Use custom images with the IaaS API
• STACKIT docs: Machine types
• StackToIT docs: VMware to STACKIT
• STACKIT: Coriolis appliance installer (GitHub)