jcoffey-dev
5a4c175042
The phases have all existed for a while; nothing chained them. The order
here is the one arrived at by performing this migration by hand against a
clone of production before writing it down:
preflight -> stage -> dump -> preserve binary -> STOP ->
convert -> supplement -> recovery-mode migration -> cutover -> START
The dump runs before the stop because it reads settings over the admin API,
and a stopped server has no admin API. Everything from the stop to the end
of cutover is downtime.
internal/stage fills the last missing phase (4.3): resolve the release,
take the x86_64 linux-gnu server build and refuse to substitute another,
verify a pinned checksum if one was given, extract the binary - refusing
any archive entry that isn't a regular file, since a tarball is untrusted
input - and confirm the result reports the version its tag claimed.
Everything upstream of that last check is an assumption about someone
else's release process.
Two gates, separate on purpose. --yes is about intent. --recovery-point-
confirmed is a claim about the world: this tool cannot undo a migration
(4.8) and cannot check whether a snapshot exists, so a run that proceeded
without the operator asserting one would be proceeding on a hope.
Verified end to end against a real Stalwart 0.15.5 with email-style account
names, a named admin account, and seeded mail:
MIGRATION COMPLETE. Mail was down for 6s.
Every cutover step green, including recalculate-quotas ("rebuilt disk
quotas for 2 account(s)") - the first time the x:Task wire format inferred
from Stalwart's schema reference has actually been exercised. It works,
now that endpoint discovery and role restoration make it reachable. After
the migration the named admin still administers, alice logs in with
unchanged credentials to the same four messages, and new SMTP delivery is
accepted.
Both refusal gates were tested, as was the failure path: an apply that
fails leaves the run stopped with the store part-migrated, and the error
says to restore the recovery point rather than restart the old version
against it.
261 lines
11 KiB
Markdown
261 lines
11 KiB
Markdown
# stalwart-migrator
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In-place upgrade tool for Stalwart Mail Server, 0.15.5 → latest: no data
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loss, a checkpoint at every step so an interrupted run resumes instead of
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restarting, and automated validation that the server still works afterwards.
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**Recovery from a failed migration is your own snapshot or backup — this
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tool does not undo a migration.** See [Recovery is your
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job](#recovery-is-your-job) before using it on anything you care about.
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Go, standard library only — no external dependencies.
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## Status
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Partially implemented. Roughly 8,800 lines of tested code. Every phase
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except staging now exists as a package, including cutover, but nothing wires
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them into a production run yet, so `run` still refuses.
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| Command | State |
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|---|---|
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| `stalwart-migrate preflight` | **Works** — read-only checks and a migration plan |
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| `stalwart-migrate rehearse` | **Works** — read-only; converts your settings and reports what won't carry over |
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| `stalwart-migrate run` | **Works** — performs the migration; `--recovery-point-confirmed --yes` |
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| `stalwart-migrate status <id>` | **Works** |
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| `stalwart-migrate report <id>` | Not implemented |
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**`run` performs the migration**, in the order
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preflight → stage → dump → stop → convert → recovery-mode → cutover. It
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needs two flags: `--yes` (intent) and `--recovery-point-confirmed` (a claim
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that you have a snapshot or backup you have verified you can restore — this
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tool cannot undo a migration and will not start without it).
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**Start with `rehearse` first.** It is read-only, needs no maintenance
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window, and tells you what `run` will and won't carry over.
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Measured on a full migration: the store converts in seconds, and the service
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was down for **6 seconds** end to end. Plan the window around verification,
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not data volume.
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Package state:
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| Package | Lines | Tests |
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|---|---|---|
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| `internal/backup` | 1806 | yes |
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| `internal/preflight` | 1329 | yes |
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| `internal/stalwartapi` | 1276 | yes |
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| `internal/cutover` | 1186 | yes |
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| `internal/validate` | 792 | yes |
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| `internal/recovery` | 702 | yes |
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| `internal/checkpoint` | 556 | yes |
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| `internal/service` | 467 | yes |
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| `internal/plan` | 195 | yes |
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| `internal/config` | stub | — |
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## Why not a shell script
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Stalwart's 0.15 → 0.16 boundary is not a drop-in binary swap: settings move,
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and the data directory has to be migrated rather than merely copied. The
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failure mode that matters is a half-migrated mail store with no way back —
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which is why backup verification and checkpointing are the design centre
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rather than conveniences bolted on afterwards — and why the tool refuses to
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cut over until you confirm you have a way back.
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[`ARCHITECTURE.md`](ARCHITECTURE.md) covers this in full: §1 on why a thin
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wrapper is insufficient, §4 on the migration phases, §5 on the checkpoint
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state machine, §6 on the CLI surface, and §8 on what is still open.
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## Build and test
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```sh
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go build ./...
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go test ./...
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```
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Requires Go 1.26 or newer.
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## Trying it safely
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`preflight` is the sensible starting point — its checks against the Stalwart
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installation are read-only:
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```sh
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sudo go run ./cmd/stalwart-migrate preflight
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```
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It still needs write access, because it records the run as a checkpoint
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before doing anything else:
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```
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create run: checkpoint: create run directory:
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mkdir /var/lib/stalwart-migrator: permission denied
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```
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That path is `checkpoint.DefaultBaseDir`, a compile-time constant with no
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flag or environment override — so preflight needs either root or a
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pre-created writable `/var/lib/stalwart-migrator`. (`run` takes `--work-dir`
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for its scratch space, but that is a different directory and does not move
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the checkpoint store.)
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`rehearse` is the next step, and unlike everything else here it is worth
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running today — see the next section.
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## Rehearse before you migrate
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```sh
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stalwart-migrate rehearse --admin-url https://mail.example.com \
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--admin-user admin --target 0.16.14
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```
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It runs preflight, dumps your settings and principals, converts them with
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Stalwart's own `migrate_v016.py`, and reports **both halves** of the result:
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the apply plan of what will carry over, and the worklist of what will not.
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It copies no data, clones nothing, starts no server, and never writes to the
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store, so it is safe to run against production repeatedly and without a
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maintenance window.
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It also generates a **supplemental plan** for the part it can rebuild
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automatically — currently your network listeners, which is the difference
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between a migrated server that answers and one that doesn't — and reports
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exactly how much of the worklist that covers (on a test instance: 24 of
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3,505 keys, and it says so rather than implying more). Review it, then apply
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it after `export.json`:
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```sh
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stalwart-cli apply --file <state-dir>/runs/<run-id>/supplement.json \
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--url https://mail.example.com
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```
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The worklist is long but mostly not work, and `rehearse` says which is
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which. Measured against a real production instance, `migrate_v016.py`
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carried **219 of 12,401 settings**. Of the 12,182 it left:
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- **8,547** are runtime auto-ban state that repopulates itself
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- **3,337** are stock spam-filter and lookup data v0.16 ships its own copies
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of — restoring v0.15's would revert a year of upstream updates
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- **~224** were already carried another way, DKIM signatures included
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- **~293** genuinely need your eyes
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`server.listener` is in that third group only because this tool regenerates
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it for you; without that a migrated instance answers on no ports at all. Both outputs are preserved
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under `<state-dir>/runs/<run-id>/` (`export.json` and `unmigrated.txt`) even
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though the rest of the scratch directory is cleaned up, because they are the
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conclusions.
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This replaced an earlier `run --dry-run` that cloned the data directory into
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a sandbox and migrated the copy. That proved the store opens, at the cost of
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copying it twice — while the half that found every real problem needed no
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copy at all. ARCHITECTURE.md §4.9 has the reasoning.
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## You need a named admin account before you migrate
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**A config-file fallback admin will not survive the migration.** If the only
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administrator you have is an `[authentication.fallback-admin]` block in
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`config.toml` — which is what `stalwart --init` sets up — you will come out
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of the migration unable to administer the server.
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Create a real account in the directory, with the admin role, and confirm you
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can log in as it *before* migrating. Three separate reasons, all verified
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against a real 0.15.5 → 0.16.14 migration:
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1. **v0.16 keeps its configuration in the store, not in a file.** After the
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migration the server is started with a config that is little more than a
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pointer at the data store, so the old `config.toml` — and the
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fallback-admin block inside it — is no longer read at all. That
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credential simply stops existing.
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2. **`migrate_v016.py` gives every migrated account the `User` role**,
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whatever it held before. An account that was an administrator in v0.15
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comes out authenticating normally and refused every management
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operation. `rehearse` generates the operation that restores it — but the
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account has to exist in the directory for there to be anything to
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restore.
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3. **The account's local part must be unambiguous.** v0.16 identifies an
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account by local part plus domain, so if `[email protected]` and
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`[email protected]` both exist, this tool will refuse to restore either
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role rather than risk granting administrator rights to the wrong one.
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It says so rather than guessing; you then grant it by hand.
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The practical check: before you migrate, make sure you can authenticate to
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the admin API as a directory account — not as the fallback admin — and that
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its local part is unique across your domains.
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## Recovery is your job
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**This tool does not undo a migration.** There is no `rollback` command.
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Recovery from a failed migration is your own snapshot or backup, taken by
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whatever method you already trust and know how to restore — a ZFS, LVM or
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btrfs snapshot, a VM or volume snapshot, or a restorable backup. Choosing
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that method, taking it, and verifying you can actually restore from it is
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out of scope for this tool: it does not take one, does not check that one
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exists, and cannot restore from one.
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Cutover refuses to start until you confirm a recovery point exists. That
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confirmation is an acknowledgement, not a check — nothing here can verify
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your snapshot. Its only purpose is that nobody migrates a production mail
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server having never been asked the question.
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**Take the snapshot with the service stopped** if you want a clean one. A
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snapshot of a running Stalwart is crash-consistent rather than clean; RocksDB
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will usually recover from its WAL, but "usually" is doing real work in that
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sentence.
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### Restoring from a snapshot loses mail delivered since
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Reverting to any pre-migration recovery point discards mail delivered
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between taking it and restoring it. This is inherent to restoring a point in
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time and this tool cannot solve it — plan your migration window with that in
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mind, and consider holding inbound mail at a secondary MX for the duration
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if the gap matters to you.
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### What the tool does to make a manual restore easier
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- **The old binary is preserved**, never deleted, next to the new one as
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`<binary>.v<old-version>` — so putting things back doesn't depend on
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re-downloading a specific old release under pressure.
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- **The original service definition is preserved** as `<unit>.pre-<run-id>`
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before cutover rewrites it, so you aren't reconstructing a unit file from
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memory.
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- **The settings and principals dumps** taken during backup stay on disk.
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- **Every artifact path and checksum is in the checkpoint**, and
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`stalwart-migrate status <run-id>` prints exactly which steps completed
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and which failed — which is the first thing you want when deciding what to
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restore.
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None of this is a substitute for the snapshot. It's what makes the twenty
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minutes after restoring one less unpleasant.
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### Why it works this way
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An earlier version of this tool implemented rollback itself: it restored the
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filesystem backup, verified every restored file against a manifest, replayed
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SQL dumps, reinstalled the old binary, and re-validated the result. It was
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tested and it looked good. It was removed, because restoring bytes correctly
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is not the hard part — it copied contents and permissions but not
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*ownership*, so run as root it would have produced a byte-perfect,
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checksum-verified, root-owned data directory that Stalwart, running as its
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own user, could not open, and it would have reported success. A filesystem
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snapshot has no such failure mode, because it never lost the metadata to
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begin with. ARCHITECTURE.md §4.8 records the full reasoning.
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## License
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Copyright (C) 2026 LINUXexpert-org
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This program is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the Free
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Software Foundation, either version 3 of the License, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details.
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You should have received a copy of the GNU General Public License along with
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this program. If not, see <https://www.gnu.org/licenses/>.
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The full text is in [`LICENSE`](LICENSE). No third-party code is vendored —
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this tool is standard library only, and the `migrate_v016.py` it downloads
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at runtime is Stalwart's own script, fetched rather than redistributed.
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