Feature Deprecations

This section tracks features removed in 27 and features deprecated in 27 for future removal. Plan migrations immediately to avoid disruptions during upgrades.

Legacy virtual machines created using the Instances screen in 25.04.0 and 25.04.1, and still shown on the Containers screen through 25.10, are removed in TrueNAS 26. No migration tool, wizard, or notification exists to move them automatically. Containers migrate automatically during the upgrade. These legacy VMs do not.

Migration Path:

1. While still running TrueNAS 25.10, record the configuration of each legacy VM and the location of the disk on the pool.
2. Upgrade to TrueNAS 26.
3. Re-create the VM and reattach the disk using the migration procedure.

Impact: A legacy VM does not appear anywhere in TrueNAS 26 after the upgrade. The VM disk remains on the pool, but you must re-create the VM configuration by hand and reattach the disk to it.

See Also:

• Migrating Legacy VMs to Virtual Machines

The TrueNAS REST API has been fully replaced by the versioned JSON-RPC 2.0 Websocket API.

Migration Path:

1. Review current API integrations and identify all REST API calls.
2. Review the Websocket API documentation to identify replacement endpoints.
3. Update all scripts and integrations to use Websocket API endpoints.
4. Test thoroughly in a non-production environment.
5. Deploy updated integrations before upgrading to 27.

Impact: Systems still using the REST API must migrate to the Websocket API before upgrading to 27. REST API endpoints do not function in 27 and later.

See Also:

• Websocket API Documentation
• Managing API Keys

The pool.is_upgraded method, which reported whether a pool had all ZFS feature flags enabled, is removed in TrueNAS 27. No direct replacement is provided. Scripts that need to inspect pool feature flag state can use pool.query and read the returned feature flag information.

The pool.ddt_prefetch method, which prefetched deduplication table (DDT) entries for a pool, is removed in TrueNAS 27. Use pool.prefetch instead, which prefetches both DDT and Block Reference Table (BRT) metadata in a single call.

The auth.login and auth.login_with_api_key methods are deprecated and scheduled for removal in TrueNAS 27. Migrate to auth.login_ex:

• Replace auth.login with auth.login_ex using mechanism="PASSWORD_PLAIN". For two-factor authentication, follow with auth.login_ex_continue using mechanism="OTP_TOKEN".
• Replace auth.login_with_api_key with auth.login_ex using mechanism="API_KEY_PLAIN" (or mechanism="SCRAM" for stronger mutual authentication).

Removing the legacy auth.login and auth.login_with_api_key entry points does not affect API_KEY_PLAIN or the other non-SCRAM mechanisms on auth.login_ex, which remain supported beyond TrueNAS 27.

See the SCRAM Authentication primer for guidance on implementing SCRAM in custom API clients and migrating pre-TrueNAS 27 API keys to the optimized precomputed format.

The pool.scrub.run and pool.scrub.scrub methods are deprecated. Use zpool.scrub.run to start, stop, or pause pool scrub operations. A removal version is not yet defined.

The consolemsg attribute on system.advanced.config and system.advanced.update is deprecated. Use the ui_consolemsg attribute on system.general.config and system.general.update instead. A removal version is not yet defined.

The pool_keys parameter on config.save is deprecated and already ignored — passing it has no effect on TrueNAS configuration backups. The parameter remains accepted for backward compatibility. A removal version is not yet defined.