Software release notes

Line 3.x · current release 3.4.2 · page updated 2026-08-24

Upgrade paths

Within 3.x you may jump straight to the current release from 3.2 or later. From 3.0 and 3.1 there is one stop on the way, because the meter database was rebuilt in 3.2 and the migration only knows how to read the older format.

From	Go to	Then	Why
3.0.x	3.2.4	3.4.2	Meter database migration.
3.1.x	3.2.4	3.4.2	Meter database migration.
3.2.x	3.4.2	—	Direct.
3.3.x	3.4.2	—	Direct.

Downgrading below 3.2 is not possible once the database has been migrated. update rollback goes back exactly one release and refuses to cross that line. Take a backup before every upgrade and this never matters.

How to upgrade

mluctl backup create --to usb
mluctl release drain          # if secure release is in use
mluctl update check
mluctl update apply           # or: mluctl update apply --file /mnt/usb/mlu-3.4.2.ipk
mluctl status                 # after the unit comes back

The unit is unavailable for three to six minutes. Meter collection catches up on the next pass with no gap in the daily figures, because counters only go up. Held jobs survive an upgrade — they do not survive a replacement.

Releases

3.4.2 — 2026-08-18

Fixed: a device whose serial number contained a space was re-created as a new record on every scan, splitting its meter history.
Fixed: scheduled exports produced an empty file when the period ended on a day the unit was restarted.
Alert MLU-309 (ambient temperature) no longer fires during the first two minutes after boot, when the sensor reads high.

3.4.0 — 2026-07-06

Supply estimates now show a confidence band and fall back to a plain percentage below seven days of history, instead of producing dates that were confidently wrong.
New: mluctl release drain, so that maintenance no longer means either losing jobs or waiting for the queue to empty by luck.
New: per-device supply offsets, for platforms that report the level of the rated cartridge rather than the one fitted.
Alert digest for informational codes, one mail at 07:30 instead of a stream.
Console: device list gained the profile-match column. A generic match is now visible without opening each device.

3.3.1 — 2026-04-22

Fixed: SNMPv3 devices that answered status but not meter OIDs were marked unreachable rather than partially readable.
Fixed: the closing read could run before the last four-hourly pass on sites west of UTC.

3.3.0 — 2026-03-10

Shell access is disabled by default on new units. Existing units keep their setting on upgrade.
Discovery no longer retries a credential after two authentication failures, which was locking SNMPv3 accounts on two platforms.
New: --json on every command that prints a table, with a documented stable format.
Recovery image and update package are the same file; one fewer thing to carry.

3.2.4 — 2026-01-28

Migration target for units on 3.0 and 3.1. Stable release, kept available indefinitely.
Fixed: counter resets were recorded twice when the reset happened between the closing read and midnight.

3.2.0 — 2025-11-17

Meter database rebuilt: daily closing readings separated from raw polls, giving three-year history within the storage of a standard unit. This is the migration step in the table above.
Removed: automatic colour-to-mono conversion when moving a held job between pools. It produced grey invoices at one site for three months before anyone noticed. Moves are now refused with a reason instead.
Counter runs and reset annotation, replacing the older behaviour of silently subtracting.

3.1.0 — 2025-08-05

Secure release printing added as an optional feature: hold queue, pools, PIN and card identification.
Quiet hours and flap protection for alerts.

3.0.0 — 2025-05-13

First release of the 3.x line. Rewritten collection service, profile matching, the mluctl command set and the current console.
Units on the 2.x line were replaced rather than upgraded; there is no migration path and no reason to look for one.