OK, encontrei boa documentação sobre isso. Se alguém tiver uma resposta melhor ou alguma nota, poste-a.
The Update Process
Run the following steps, whether you are updating a Samba Active Directory (AD) domain controller (DC), a Samba NT4-style PDC, a Samba domain member, or a standalone installation:
Stop all Samba services.
Create a backup.
Read the release notes of skipped versions. They contain important information, such as new features, changed parameter, and bug fixes. In case you switch to new major release, read the release notes of the initial version (x.y.0) and the ones from minor versions up to the new version you will update to. For example, if you update from 4.4.4 to 4.6.2, read the 4.5.0, 4.6.0, 4.6.1, and 4.6.2 release notes.
Install the latest version over your existing one:
If you compile Samba from the sources, use the same configure options as used for your previous version. For more information, see Build Samba From the Sources.
If you update using packages, read the distribution documentation for information how to update.
Start Samba.
Start the same daemons as on your previous version:
On Samba AD DCs: samba
On Samba NT4-style PDC/BDCs: smbd, nmbd
On Samba domain members: smbd, nmbd (winbind, if used)
On Samba standalone hosts: smbd
On Samba AD DCs only: Run the Samba AD DC database check.
Check your Samba log files for errors.
Test your updated installation.