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terraform-proxmox-vm

A Terraform module to create Proxmox VMs with support for:

  • butane/ignition configurations
  • virtiofs filesystems
  • plan9f filesystems

A butane configuration provides a human readable YAML configuration to perform first time boot configuration of a VM with a machine readable JSON ignition configuration.

Virtiofs allows directories to be exported from the host into a VM. First class support for virtiofs is not available in Proxmox VE v8.0, but work is being done to provide native support for virtiofs.

Proxmox VE v8.0 supports a single hookscript per VM. If extending the functionality of Proxmox VE via a hookscript then a single monlithic hookscript doesn't allow modular extension of functionality. This module provides support for multiple proxmox hookscripts.

The Proxmox API is highly constrained. The Proxmox provider used is further constrained. This module is a series of compromises and workaround to allow a VM to be provisioned within seconds.

This module allows multiple VMs to be provisioned at once. This is useful for provisioning small static k8s/k3s clusters.

This module has been developed with Proxmox VE v8.x. The VM being provsioned is usually Flatcar Linux (to run container workloads). However there is nothing specific about this script that requires the VM to be running flatcar.

Prerequisites

To use this Terraform module, the following pre-requisites must be met:

  1. Add your root proxmox credentials to a .tfvars file
  2. Install the hookscript on your Proxmox host, into the local:snippets storage
  3. Create a VM template (e.g. Flatcar Linux) (see example makeflatcarproxmoxtemplate)
    • the template must have the hookscript set to multi-hookscript.pl
  4. Install terraform-provider-proxmox v3.0.1-rc4 or greater
  5. Install virtiofsd (rust) in /usr/local/bin

The example scripts require a .tfvars file with your proxmox URL, username, and password.

Three hookscripts are provided with this module. They must be available in a snippets directory and must be executable. They have been tested in the local: storage, which maps to /var/lib/vz/ directory.

A VM template needs to be created that this module can clone. This can be any operating system that you choose that has ignition support and/or virtiofs support as required. The template must set the hookscript to local:snippets/multi-hookscript.pl (this is because it is not supported to set the hookscript via the terraform module)

Compile or copy the [virtiofsd](https://share.lucidsolutions.co.nz/pub/debian/bookworm/virtiofsd-1.8.0/) to user/local/bin so that directories can be shared with virtiofs.

Multi-hookscript

Support for multiple hookscripts is provided via a hookscript. The multi-hookscript script reads its configuration from the VM description. It then chains all calls for each phase to the configured scripts. This allows small functional hookscripts to be added to the system.

It is hoped that at some stage the proxmox configuration and the API could support multiple hookscripts natively. This would mean the description field of the configuration would not need to be hijacked for this purpose.

Butane/Ignition

This support allows 'cattle' (c.f. 'pet) type VM's to be configured via a Terraform provisioning script. This is not natively supported by Proxmox VE v8.x. Proxmox VE v.8.x does support cloud-init.

Testing of this feature has been done with Flatcar Linux.

The terraform script transfers the ignition configuration as a resource to a cloud-init ISO image in Proxmox VE with a name based on the VM id. The hookscript is then configured to extract the configuration from the cloud-init ISO at VM pre-start phase and put it in the /etc/pve/local/ignition/<VM_ID>.ign file. The QEMU arguments reference this file as a firmware configuration via the fw_cfg option. The ignition JSON content can be viewed in the target Linux VM in the file /sys/firmware/qemu_fw_cfg/by_name/opt/org.flatcar-linux/config/raw.

This module will create an ignition configuration per VM (when multiple VMs are provisioned). This means that small tweaks per VM can be specified (however this moves the VMs further away from being 'cattle'). A minimal set of variables are passed through to the Butane configuration render function.

Virt IO Filesystem

This supports exporting directories from the Proxmox host into a VM. Multiple directories are supported.

The VM operating system must support virtiofs (CONFIG_VIRTIO_FS) to allow it to mount the host directory. At the time of writing Flatcar Linux doesn't support virtiofs, however Alpine Linux does support virtiofs.

The virtiofs support is implemented via QEMU arguments and running an instance of the rust based virtiofsd daemon per shared directory. A precompiled x86_64 rust binary is available here, or it can be compiled from source.

Although Proxmox VE v8.x doesn't support virtio filesystem, there are patches. Support for the API is promised. The changes to his script should be minimal when that support arrives. The names are variables used by this module have been taken from the patch to ease future transition.

Plan9 Filesystem

This supports exporting directories from the Proxmox host into a VM. Multiple directories are supported.

If the VM supports virtiofs then it seems a better option. As of November 2023, Flatcar Linux doesn't support virtiofs so the plan9fs is used for these VMs.

The terraform for plan9fs support doesn't need a hookscript or a daemon. It simply sets the QEMU options at VM configuration time.

Known Limitations

As of November 2023, the following limitations and residuals have been observed:

  1. The Proxmox API requires the 'root@pam' user to provision 'args'. Using an API key doesn't work, and using an API key for root also doesn't work, as the username 'root@pam!terraform' doesn't match the required identity of 'root@pam' which is hardcoded in some places.

  2. The Qemu command line parsing requires the Ignition configuration to have all comma's escaped with another comma (i.e. a double comma). This means it is far easier and more successful to use the 'file=' option (rather than 'string=') fw_cfg option.

  3. When creating a Proxmox UEFI VM with a pre-made image, the special file=<storage>:0 syntax must be used. e.g. if the node local disk is called 'local' then the syntax would be:

   --efidisk0 "file=local:0,import-from=flatcar_production_qemu_image.img,efitype=4m,format=raw,pre-enrolled-keys=1"

  1. Although the flatcar linux qemu image has a .img extension, it is a qcow2 formatted file. The image has multiple partitions.

  2. The documentation isn't clear as to the correct way to mount UEFI code partitions as a read-only volume. It is unclear how to specify a pflash drive for the UEFI code. To see the Qemu configuration run qm showcmd <vm id> --pretty, which shows the two EFI pflash drives.

  3. The Terraform Telmate/Proxmox provider doesn't support setting the hookscript upon create, thus the hookscript must be set in the template and inherited to child VM's.

  4. The proxmox hook script locks the vm configuration - thus stopping the hook script from modifying/mutating the configuration. Even if the configuration is changed the Proxmox start code will not reload the changes after the hookscript runs.

  5. There appears to be limitation on the length of the ignition file to about 8k when it is put into the description field. It is unclear where this limitation is imposed, as the internal code seems to limit the description field to 64kbytes. This renders the strategy of hijacking the description field as ineffective for all but trivial VM's. The description field is changeable by a user in the 'notes' section of the UI - changing the description may break the hookscript configuration. Markdown is used in the description to try and make clear which bit is configuration.

  6. The Terraform provider Telmate/Proxmox can generate duplicate MAC addresses when provisioning multiple VMs. IPv6 notices the duplicate/collision and doesn't complete SLAAC, thus the VM doesn't get IPv6 addresses.

Links

Flatcar

Ignition

Terraform

Proxmox

Qemu

UEFI