TrueNAS ZFS-over-iSCSI Plugin for Proxmox VE

A Proxmox VE storage plugin that manages ZFS-over-iSCSI volumes on TrueNAS (CORE and SCALE) through the TrueNAS REST API — no SSH-based LUN management, no iscsiadm scripting.

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Table of Contents

• How It Works
• Compatibility
• Prerequisites
• Installation
• Configuration
• Upgrading
• Uninstalling
• Troubleshooting
• Contributing
• Support the Project
• License

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How It Works

Proxmox VE's built-in ZFS-over-iSCSI storage type uses SSH to manage LUNs on the storage server. This plugin replaces that SSH-based management layer with direct calls to the TrueNAS REST API, giving you:

• API token (Bearer) or username/password authentication
• Automatic TrueNAS API version detection (v1 and v2)
• Support for both TrueNAS CORE and TrueNAS SCALE
• Proper rollback when operations fail (no dangling iSCSI extents)

Note: Proxmox still uses iscsiadm to connect and disconnect the iSCSI session on the Proxmox host itself — that part is handled by the core Proxmox code and does not require SSH. The SSH keys documented in the Proxmox ZFS-over-iSCSI wiki are still required for the ZFS pool listing step.

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Compatibility

Version Matrix

Plugin Version	Proxmox VE	TrueNAS CORE	TrueNAS SCALE	Status
3.x (upcoming)	8.x, 9.x	13.0-U6+	Cobia (23.10)+, Dragonfish (24.04)+	In development
2.x (current)	7.x ⚠️, 8.0–8.3 ✅, 8.4.x ✅	11.3+	22.02+	Active
1.x (legacy)	5.x, 6.x	11.x	—	Unsupported

Important Version Notices

Proxmox VE 7 users

v2.x is the last release series that supports PVE 7. PVE 7 support is best-effort only — no new patches will be developed for it.

Do not upgrade to v3.0 when it releases — v3.0 requires Proxmox VE 8 or later. Stay on the latest v2.x release.

Proxmox VE 8 users

Proxmox VE 8 reaches end-of-life on 2026-08-31. Plan your upgrade to PVE 9 before that date.

v2.x works on PVE 8. When you upgrade to PVE 9, migrate to v3.0 (coming before the EOL date).

Proxmox VE 9+ users

v2.x is not supported on PVE 9. Use v3.0 when it is released. Do not install v2.x on a PVE 9 node.

Proxmox VE 5 or 6 users

These versions are not supported. PVE 5 reached end-of-life in 2019, PVE 6 in 2022. Please upgrade your Proxmox VE installation.

Check the Releases page for the specific Proxmox and TrueNAS versions tested against each release.

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Prerequisites

Before installing, ensure the following are in place on your Proxmox VE node:

1. SSH keys configured between Proxmox and TrueNAS — required for ZFS pool listing by the Proxmox core (see the Proxmox wiki, section starting with mkdir /etc/pve/priv/zfs).

2. On TrueNAS, an iSCSI target and initiator group must exist and be configured. The plugin manages extents and target-to-extent mappings, but the target itself must be pre-created.

3. On TrueNAS SCALE or TrueNAS CORE 13+, generate an API key:

   • TrueNAS SCALE: System Settings → API Keys → Add
   • TrueNAS CORE 13: gear icon (top-right) → API Keys → Add

   Copy the key — you will need it during storage configuration in Proxmox.

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Installation

Stable Release

Add the repository and install:

# Import the GPG key
curl -fsSL https://dl.cloudsmith.io/public/ksatechnologies/truenas-proxmox/gpg.284C106104A8CE6D.key \
  | gpg --dearmor \
  | tee /usr/share/keyrings/ksatechnologies-truenas-proxmox-keyring.gpg > /dev/null

# Add the repository
cat > /etc/apt/sources.list.d/ksatechnologies-repo.list << 'EOF'
deb [signed-by=/usr/share/keyrings/ksatechnologies-truenas-proxmox-keyring.gpg] \
  https://dl.cloudsmith.io/public/ksatechnologies/truenas-proxmox/deb/debian any-version main
EOF

# Install
apt update && apt install freenas-proxmox

Testing / Beta Release

For early access to new features (may be unstable):

# Import the GPG key
curl -fsSL https://dl.cloudsmith.io/public/ksatechnologies/truenas-proxmox-testing/gpg.CACC9EE03F2DFFCC.key \
  | gpg --dearmor \
  | tee /usr/share/keyrings/ksatechnologies-truenas-proxmox-testing-keyring.gpg > /dev/null

# Add the repository
cat > /etc/apt/sources.list.d/ksatechnologies-testing-repo.list << 'EOF'
deb [signed-by=/usr/share/keyrings/ksatechnologies-truenas-proxmox-testing-keyring.gpg] \
  https://dl.cloudsmith.io/public/ksatechnologies/truenas-proxmox-testing/deb/debian any-version main
EOF

# Install
apt update && apt install freenas-proxmox

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Configuration

After installation, refresh your browser to load the updated Proxmox UI. Then add a new ZFS-over-iSCSI storage:

1. Navigate to Datacenter → Storage → Add → ZFS over iSCSI
2. Set iSCSI Provider to FreeNAS/TrueNAS API
3. Fill in the storage fields — see below for authentication options

Authentication: API Token (Recommended)

Field	Value
Portal	IP or hostname of your TrueNAS server
Target	The iSCSI target IQN
Pool	The ZFS pool name
Use SSL	Enabled (recommended)
API Host	Leave blank to use Portal IP, or specify a separate management IP
Use Token Auth	Enabled
API Token	Paste the TrueNAS API key you generated

Authentication: Username / Password (Legacy)

Field	Value
Use Token Auth	Disabled
Username	TrueNAS API user (usually root)
Password	TrueNAS user password

Security note: Username/password authentication sends credentials on every API call. API token authentication is preferred and may be required in future TrueNAS releases.

ZFS Block Size

The ZFS Blocksize field controls the -b argument passed to zfs create when Proxmox provisions a new zvol on TrueNAS. Set this when adding the storage — it cannot be changed afterward without editing the config directly.

TrueNAS Product	Recommended blocksize
TrueNAS SCALE (any version)	16k (16384)
TrueNAS CORE	8k (8192)

TrueNAS SCALE ships a newer ZFS that requires a minimum block size of 16k. If you leave this at the Proxmox default of 8k on a SCALE system, every disk creation will log:

Warning: volblocksize (8192) is less than the default minimum block size (16384).
To reduce wasted space a volblocksize of 16384 is recommended.

The disk is created successfully despite this warning, but the suboptimal block size wastes space due to internal ZFS padding on every write.

Fixing an existing storage entry:

Edit /etc/pve/storage.cfg on any cluster node and change blocksize 8192 to blocksize 16384 for your TrueNAS SCALE storage entry. No data migration is needed — only newly created zvols use the updated value. Existing zvols are unaffected.

Note: Automatic blocksize detection based on TrueNAS version is planned for v2.4.0 (see #241).

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Upgrading

The package integrates with Proxmox VE's standard upgrade mechanism. On apt upgrade, the package will automatically re-apply any patches needed after a Proxmox VE update:

apt update && apt full-upgrade

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Uninstalling

apt remove freenas-proxmox

This removes the plugin and reverses all patches, returning your Proxmox VE installation to its unmodified state. Any storage configurations using this plugin should be removed from Proxmox before uninstalling.

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Troubleshooting

After install, the "FreeNAS/TrueNAS API" option is not visible

Refresh your browser (force-refresh with Ctrl+Shift+R or Cmd+Shift+R). The Proxmox UI JavaScript is cached aggressively.

Storage shows as unavailable / API connection fails

Check journalctl -f or /var/log/syslog on the Proxmox node — the plugin logs all API calls and errors with [FreeNAS::API::] prefixes.

Common causes:

• Wrong API host or portal IP
• SSL mismatch (try toggling SSL on/off)
• API token expired or revoked
• TrueNAS iSCSI service not running

"volblocksize is less than the default minimum block size" warning on disk creation

This warning appears on TrueNAS SCALE when a zvol is created with a blocksize below 16k.

v2.4.0 and later: the plugin automatically detects the correct blocksize from the TrueNAS API and corrects it. If you see a line like freenas-proxmox: blocksize 8192 < recommended 16384 -- correcting storage '...' in the task log, the correction was applied and the disk was created correctly. The storage config is also updated automatically so subsequent disk creations will be silent.

v2.3.x and earlier: see ZFS Block Size — manually set the blocksize to 16k for SCALE storages.

API key stops working after upgrading TrueNAS SCALE to 25.04

TrueNAS SCALE 25.04 revokes all existing API keys that were created with whitelisted methods during the upgrade. If you are using truenas_token_auth and your storage shows as unavailable after a SCALE 25.04 upgrade, your API key was revoked.

Fix:

1. Log into the TrueNAS SCALE web UI
2. Go to Credentials → API Keys and generate a new API key
3. In Proxmox, edit the affected storage (Datacenter → Storage → Edit) and paste the new key into the API Secret / Token field

Additionally, TrueNAS SCALE 25.04 enforces HTTPS for API key authentication — keys transmitted over plain HTTP are automatically revoked. Ensure Use SSL is enabled in your Proxmox storage config when using token auth.

Note: TrueNAS SCALE 25.04 also deprecates the REST API used by this plugin (v2.x). Full removal is planned for SCALE 26.x. Plugin v3.0.0 will add WebSocket JSON-RPC 2.0 support. See issue #243.

Dangling extents on TrueNAS after a failed operation

If you see iSCSI extents in TrueNAS that are not associated with any target, they can be safely deleted from the TrueNAS UI. v2.3.0 and later automatically roll back and clean up after a failed LUN creation.

Filing a Bug Report

Please use the GitHub issue tracker and include the bug report template. Include relevant log lines from syslog (search for FreeNAS::).

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Contributing

Contributions are welcome. Please read CONTRIBUTING.md before opening a pull request.

For significant changes, open an issue first to discuss the approach.

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Support the Project

If this plugin saves you time, consider supporting its development:

• GitHub Sponsors: github.com/sponsors/TheGrandWazoo
• PayPal: Donate via PayPal

Donor support has funded a 4-node Proxmox cluster and TrueNAS test lab used for development and validation. See DONORS.md for a full list of donors.

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License

Copyright (c) 2020 KSA Technologies, LLC

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, version 3.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.