Downgrading Samba

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Short version: data-preserving downgrades between Samba versions are not supported

Long version:

With Samba development there are cases when on-disk database format evolves.

In general, Samba Team attempts to maintain forward compatibility and

automatically upgrade databases during runtime when requires.

However, when downgrade is required Samba will not perform downgrade to

existing databases. It may be impossible if new features that caused database

upgrade are in use. Thus, one needs to consider a downgrade procedure before

actually downgrading Samba setup.

Please always perform back up prior both upgrading and downgrading across major

version changes. Restoring database files is easiest and simplest way to get to

previously working setup.

Easiest way to downgrade is to remove all created databases and start from scratch.

This means losing all authentication and domain relationship data, as well as

user databases (in case of tdb storage), printers, registry settings, and winbindd

caches.

Remove databases in following locations:

/var/lib/samba/*.tdb

/var/lib/samba/private/*.tdb

In particular, registry settings are known to prevent running downgraded versions

(Samba 4 to Samba 3) as registry format has changed between Samba 3 and Samba 4.