Release version 7.1.2

The zfs snapshot was read through <subject>/.zfs/snapshot/<name>. The
kernel automounts that directory through a usermode helper that runs in
the host's mount namespace, so a containerised baudolo never sees the
mount and finds no snapshot. The snapshot is now mounted explicitly at
<subject>/.baudolo-<tag>, beside where btrfs carves its own, and removed
in order: umount, rmdir, zfs destroy. A failed mount destroys the
snapshot at once instead of leaking one per run.

The e2e suite could not reach this code at all: zpool create on the /img
file failed with "no such pool or dataset", because the kernel opens
vdevs from a taskq thread that resolves paths in the host's root, where
the container's /img does not exist. The pool now sits on a loop device,
whose /dev/loopN node the kernel creates on the host as well, and it is
destroyed on exit once this script created it, since a pool is
kernel-wide.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,148 @@
 # Changelog
 
+## [7.1.2] - 2026-10-18
+
+Fixed:
+
+- Backup: *--snapshot zfs* found no snapshot inside a container; now mounts it
+- Tests: e2e zfs pool now sits on a loop device; a file vdev never worked
+
+Upgrade notes:
+
+- Backup: zfs snapshots mount at *.baudolo-TAG* in the subject, not *.zfs*
+- Image: first ghcr image since 3.1.2; the 4.0.0 to 7.1.1 notes apply
+
+## [7.1.1] - 2026-10-17
+
+Fixed:
+
+- Tests: e2e MariaDB probe ran root passwordless and timed out at random
+- Tests: probe now logs in with the root password, skips the temp server
+- Tests: anonymous-preemption bootstrap now uses the root password too
+
+Upgrade notes:
+
+- 7.1.0 never reached stable: its CI failed, no image was published
+- 7.1.1 is the first published -aHAX build; 7.1.0 upgrade notes apply
+
+## [7.1.0] - 2026-10-17
+
+Fixed:
+
+- Backup: rsync -a stored no xattrs, ACLs or hardlinks; now -aHAX
+- Restore: restore_volume_files had the same gap; now -aHAX too
+- An OpenCloud volume lost its storage metadata through a DR drill
+
+Upgrade notes:
+
+- First backup re-copies every attribute-carrying volume once in full
+- A destination without xattr support now fails the backup run outright
+- exFAT, xattr-less NFS and object-storage FUSE mounts must move first
+
+## [7.0.2] - 2026-09-23
+
+* Backup: failed live pre-copy no longer aborts when a stopped copy follows
+* Backup: stopped --checksum copy replaces pre-copy hit by live writer (rc 23)
+* Backup: failing sole live copy or failing stopped copy still fails the run
+* Tests: e2e live writer shrinking files mid-read reproduces the rsync failure
+
+## [7.0.1] - 2026-08-18
+
+- Restore: *--empty* no longer aborts on a database that carries an extension.
+  The pre-clean picked its candidates by owner, on the stated assumption that
+  extension members are superuser-owned and would therefore never be selected.
+  That holds only when a superuser installed the extension: a role that
+  installs one itself owns its functions, so they were listed for a one-by-one
+  *DROP* that postgres refuses — *cannot drop function
+  vector_in(cstring,oid,integer) because extension vector requires it*. Under
+  *ON_ERROR_STOP* that ends the whole restore, which is how a generation of an
+  application declaring the *vector* extension became unreplayable. Membership
+  now comes from *pg_depend* rather than from ownership; each branch carries
+  its oid and classid so one *NOT EXISTS* covers all seven instead of seven
+  separate predicates, and the schema branch is guarded too because an
+  extension can own a schema. Skipping the members suffices — the dump's
+  *CREATE EXTENSION IF NOT EXISTS* finds the surviving extension either way.
+
+## [7.0.0] - 2026-08-18
+
+Breaking:
+- Backup: *mariadb* and *mysql* join the suffix tokens, so a container named
+  *<app>-mariadb* or *<app>-mysql* now resolves to the instance *<app>* instead
+  of to its own name. A *databases.csv* keyed on the full container name has to
+  move to the application name, or name the container in
+  *--database-containers*. This narrows what 6.0.0 broke rather than widening
+  it: a container named exactly *postgres*, *mariadb*, *mysql*, *db* or
+  *database* resolves again without any declaration, which is the shape a
+  compose file writes as *container_name: postgres* and the most common
+  configuration there is.
+
+Fixed:
+- Backup: a container named exactly after its engine is dumped again. The
+  suffix match needs a hyphen or underscore in front of the token, which a bare
+  name does not carry, so 6.0.0 resolved *container_name: postgres* to nothing
+  and stopped dumping it without saying so. *ENGINE_NAMES* now states the set
+  once and serves both readings — carried as a suffix it makes the rest the
+  instance, being one outright makes the container its own instance.
+- Backup: a central MariaDB under swarm is dumped for the first time. Swarm
+  names its task *mariadb_mariadb.1.<id>*, which matches neither the static
+  *mariadb* passed through *--database-containers* nor any token the suffix
+  match knew, since *_mariadb* is not *_db*. The database was silently absent
+  from every swarm backup this tool has ever written, before 6.0.0 as well.
+- Backup: an application container is no longer recorded as a database.
+  *container_engine* recognises an engine by its client tools, which an
+  application image frequently ships, so refusing its dump alone would have
+  written the volume to the manifest as *database: true, dumped: false* — the
+  exact shape a restore drill reads as a database that was missed. Without an
+  instance there is no database to record, and the volume is a file backup like
+  any other.
+
+## [6.0.0] - 2026-08-18
+
+Breaking:
+- Backup: a database container whose name carries no *database*, *db* or
+  *postgres* token — preceded by a hyphen or underscore — must now be named in
+  *--database-containers*. Without that declaration its *databases.csv* rows no
+  longer match and no dump is written, silently, because nothing fails. The
+  shape this hits hardest is a container named exactly *postgres* or *mariadb*:
+  the token needs a separator in front of it, which a bare name does not have.
+  *app-database*, *app_database.1.<task>* from swarm and *app-postgres-1* are
+  unaffected, as is any container already declared.
+
+Fixed:
+- Backup: *docker exec* now forwards *PGPASSWORD* into the container.
+  *execute_to_file* set the variable on baudolo's own process, but nothing
+  carried it across the container boundary, so an engine whose *pg_hba* demands
+  a password on TCP loopback refused every dump — which is every dedicated
+  Postgres instance on a real host. The name travels as a bare *-e NAME* so
+  docker copies the value out of this process's environment; spelling
+  *-e NAME=value* instead would publish the secret in the host's process list.
+- Backup: *get_instance* no longer claims an instance it never derived. It
+  returned the container name unchanged when that name carried no database
+  token, so an application container answered the same *databases.csv* row as
+  its own dedicated engine. Application images frequently ship the engine's
+  client tools, so the dump command started and wrote a file that looked like a
+  backup and held none of the data: measured against Discourse, 1,680 bytes
+  from the application where the engine produced 10,469,439. The regex stays a
+  normaliser — *<app>-database* from compose and *<app>_database.1.<task>* from
+  swarm still resolve to one instance. Only the fallthrough changed.
+
+New:
+- Tests: *get_instance* has unit coverage for the first time. Eleven cases pin
+  the container names that compose, swarm and explicitly-named engines produce,
+  so a future change to the regex has to state which shape it gives up.
+- Tests: two e2e modules cover shapes the suite structurally could not see.
+  Every fixture passed its container in *--database-containers*, which left the
+  regex branch — the only one a dedicated database ever takes — dead code under
+  test, and no scenario made a password mandatory, because stock
+  *postgres:alpine* grants trust on loopback.
+  *test_e2e_postgres_password_required* starts an engine with
+  *--auth-host=scram-sha-256* and carries a negative control asserting the
+  server refuses an unauthenticated dump; without it the module would pass
+  whether or not the password is forwarded at all.
+  *test_e2e_app_container_ships_client_tools* places an application container
+  beside its engine with neither declared, and requires the engine dumped, the
+  application volume copied as files, and no dump written from the application.
+
 ## [5.0.0] - 2026-08-18
 
 **[5.0.0] - 2026-08-18**

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "backup-docker-to-local"
-version = "5.0.0"
+version = "7.1.2"
 description = "Backup Docker volumes to local with rsync and optional DB dumps."
 readme = "README.md"
 requires-python = ">=3.9"
@@ -19,7 +19,7 @@ dependencies = [
 [project.optional-dependencies]
 # Pinned: a ruff minor bump changes which rules fire, and `make test` gates on
 # a clean run, so an unpinned lint would fail the suite on an unrelated day.
-lint = ["ruff==0.16.1"]
+lint = ["ruff==0.16.7"]
 
 [project.scripts]
 baudolo = "baudolo.backup.__main__:main"

src/baudolo/backup/app.py

@@ -23,6 +23,7 @@ from .layout import (
     write_manifest,
 )
 from .policy import requires_stop, volume_is_fully_ignored
+from .shell import BackupError
 from .snapshot import snapshot_source, volume_snapshot
 from .volume import backup_volume, inspect_backing
 
@@ -125,8 +126,18 @@ def main() -> int:
                     copy(authoritative=False)
                 continue
 
+            if not requires_stop(containers, args.images_no_stop_required):
                 copy(authoritative=False)
-            if requires_stop(containers, args.images_no_stop_required):
+                continue
+
+            try:
+                copy(authoritative=False)
+            except BackupError as error:
+                print(
+                    f"WARNING: live pre-copy of volume '{volume_name}' failed; "
+                    f"the copy with its containers stopped replaces it.\n{error}",
+                    flush=True,
+                )
             stoppable = filter_stoppable(containers)
             change_containers_status(stoppable, "stop")
             copy(authoritative=True)

src/baudolo/backup/db.py

@@ -16,14 +16,35 @@ if TYPE_CHECKING:
 
 log = logging.getLogger(__name__)
 
+ENGINE_NAMES = ("database", "postgres", "mariadb", "mysql", "db")
+_SUFFIX_RE = re.compile(rf"(_|-)({'|'.join(ENGINE_NAMES)})")
 
-def get_instance(container: str, database_containers: list[str]) -> str:
-    """
-    Derive a stable instance name from the container name.
+
+def get_instance(container: str, database_containers: list[str]) -> str | None:
+    """The databases.csv instance a container serves, or None for no database.
+
+    A declared container is its own instance. Every other name is read against
+    ENGINE_NAMES: carrying one as a suffix makes the rest the instance, which
+    maps `<app>-database` from compose and `<app>_database.1.<task>` from swarm
+    onto the same one; being one outright makes the container its own instance,
+    the shape a compose file writes as `container_name: postgres`.
+
+    Args:
+        container: the running container's name.
+        database_containers: names passed via --database-containers, taken as
+            declared engines whatever they are called.
+
+    Returns:
+        The instance name, or None when the name neither carries nor is an
+        engine name: an application container is not an engine, even when it
+        ships the client tools that would let a dump command start.
     """
     if container in database_containers:
         return container
-    return re.split(r"(_|-)(database|db|postgres)", container)[0]
+    parts = _SUFFIX_RE.split(container)
+    if len(parts) > 1:
+        return parts[0]
+    return container if container in ENGINE_NAMES else None
 
 
 def fallback_pg_dumpall(
@@ -37,6 +58,7 @@ def fallback_pg_dumpall(
             container,
             ["pg_dumpall", "-U", username, "-h", "localhost"],
             interactive=True,
+            forward_env=["PGPASSWORD"],
         ),
         out_file,
         env={"PGPASSWORD": password},
@@ -62,6 +84,9 @@ def backup_database(
     Returns True if at least one dump was produced.
     """
     instance_name = get_instance(container, database_containers)
+    if instance_name is None:
+        log.debug("Container '%s' carries no database token", container)
+        return False
 
     entries = databases_df[databases_df["instance"] == instance_name]
     if entries.empty:
@@ -133,6 +158,7 @@ def backup_database(
                             "--no-privileges",
                         ],
                         interactive=True,
+                        forward_env=["PGPASSWORD"],
                     ),
                     dump_file,
                     env={"PGPASSWORD": password},

src/baudolo/backup/docker.py

@@ -9,10 +9,35 @@ if TYPE_CHECKING:
 
 
 def docker_exec_argv(
-    container: str, argv: Sequence[str], *, interactive: bool = False
+    container: str,
+    argv: Sequence[str],
+    *,
+    interactive: bool = False,
+    forward_env: Sequence[str] = (),
 ) -> list[str]:
-    """The argv that runs *argv* inside *container*."""
-    return ["docker", "exec", *(["-i"] if interactive else []), container, *argv]
+    """The argv that runs *argv* inside *container*.
+
+    Args:
+        container: the container to run in.
+        argv: the command, already split.
+        interactive: keep stdin open, for a command that is fed a dump.
+        forward_env: names of environment variables to hand to the container.
+            Passed as bare ``-e NAME``, so docker copies the value out of this
+            process's own environment; spelling ``-e NAME=value`` instead would
+            publish a secret in the host's process list.
+
+    Returns:
+        The argv list.
+    """
+    forwarded = [arg for name in forward_env for arg in ("-e", name)]
+    return [
+        "docker",
+        "exec",
+        *(["-i"] if interactive else []),
+        *forwarded,
+        container,
+        *argv,
+    ]
 
 
 def get_image_info(container: str) -> str:

src/baudolo/backup/dumps.py

@@ -10,7 +10,7 @@ from pandas.errors import EmptyDataError
 
 from baudolo.databases import COLUMNS, DELIMITER
 
-from .db import backup_database
+from .db import backup_database, get_instance
 from .docker import has_tool, image_id
 
 DUMP_TOOLS: tuple[tuple[str, str], ...] = (
@@ -76,6 +76,8 @@ def backup_mariadb_or_postgres(
     engine = container_engine(container)
     if engine is None:
         return VolumeOutcome(database=False, dumped=False)
+    if get_instance(container, database_containers) is None:
+        return VolumeOutcome(database=False, dumped=False)
     db_type, dump_tool = engine
     dumped = backup_database(
         container=container,

src/baudolo/backup/snapshot.py

@@ -58,27 +58,50 @@ def _resolver(subject: str, root: str) -> Callable[[str], str]:
     return resolve
 
 
+def _remove(
+    root: str, commands: list[list[str]], run: Callable[[list[str]], list[str]]
+) -> None:
+    try:
+        for command in commands:
+            run(command)
+    except BackupError as error:
+        # Raising here would also mask whatever the body raised.
+        print(f"WARNING: {root} could not be removed: {error}", flush=True)
+
+
 def _btrfs(
     subject: str, name: str, run: Callable[[list[str]], list[str]]
-) -> tuple[str, list[str]]:
+) -> tuple[str, list[list[str]]]:
     # The snapshot goes inside the subject, never beside it: the kernel rejects
     # a snapshot whose destination is on another filesystem, which is exactly
     # what the parent directory is when the subject is a mountpoint of its own.
     target = str(Path(os.path.abspath(subject)) / f".{name}")  # noqa: PTH100 - see _resolver
     run(["btrfs", "subvolume", "snapshot", "-r", subject, target])
-    return target, ["btrfs", "subvolume", "delete", target]
+    return target, [["btrfs", "subvolume", "delete", target]]
 
 
 def _zfs(
     subject: str, name: str, run: Callable[[list[str]], list[str]]
-) -> tuple[str, list[str]]:
+) -> tuple[str, list[list[str]]]:
     output = run(["zfs", "list", "-H", "-o", "name", subject])
     dataset = (output[0] if output else "").strip()
     if not dataset:
         raise SnapshotError(f"no zfs dataset is mounted at {subject}")
-    run(["zfs", "snapshot", f"{dataset}@{name}"])
-    root = str(Path(subject) / ".zfs" / "snapshot" / name)
-    return root, ["zfs", "destroy", f"{dataset}@{name}"]
+    snapshot = f"{dataset}@{name}"
+    # Exception: mounted here rather than read through .zfs/snapshot, which the
+    # kernel automounts via a usermode helper in the host's mount namespace,
+    # so a containerised run never sees it.
+    root = str(Path(os.path.abspath(subject)) / f".{name}")  # noqa: PTH100 - see _resolver
+    run(["zfs", "snapshot", snapshot])
+    remove = [["zfs", "destroy", snapshot]]
+    try:
+        run(["mkdir", root])
+        remove.insert(0, ["rmdir", root])
+        run(["mount", "-t", "zfs", snapshot, root])
+    except BaseException:
+        _remove(root, remove, run)
+        raise
+    return root, [["umount", root], *remove]
 
 
 _CREATE = {"btrfs": _btrfs, "zfs": _zfs}
@@ -169,8 +192,4 @@ def volume_snapshot(
     try:
         yield _resolver(subject, root)
     finally:
-        try:
-            run(remove)
-        except BackupError as error:
-            # Raising here would also mask whatever the body raised.
-            print(f"WARNING: {root} could not be removed: {error}", flush=True)
+        _remove(root, remove, run)

src/baudolo/backup/volume.py

@@ -75,7 +75,7 @@ def backup_volume(
     pathlib.Path(dest).mkdir(parents=True, exist_ok=True)
 
     last = get_last_backup_dir(versions_dir, volume_name, dest)
-    cmd = ["rsync", "-aP", "--no-D", "--delete", "--delete-excluded"]
+    cmd = ["rsync", "-aHAX", "-P", "--no-D", "--delete", "--delete-excluded"]
     if authoritative:
         cmd.append("--checksum")
     if last:

src/baudolo/restore/db/empty_preclean.sql

@@ -3,8 +3,12 @@
 -- would run every DROP in one transaction and exhaust max_locks_per_transaction on
 -- large schemas (e.g. gitlab). Also drops user-owned non-public schemas so a dump
 -- that CREATE SCHEMAs (e.g. discourse's discourse_functions) does not fail on an
--- already-existing schema. Extension members (pg_trgm's set_limit) are
--- superuser-owned; IF EXISTS absorbs the CASCADE fallout.
+-- already-existing schema. Objects belonging to an extension are skipped: postgres
+-- refuses to drop them one by one ("cannot drop function vector_in(...) because
+-- extension vector requires it"), and the dump's CREATE EXTENSION IF NOT EXISTS
+-- finds the surviving extension either way. Owning them is not enough to make them
+-- droppable - an extension a role installed itself is owned by that role, so the
+-- owner filter alone lets pgvector's members through.
 SELECT format('DROP %s IF EXISTS public.%s CASCADE', obj.type, obj.name)
   FROM (
     SELECT format('%I', c.relname) AS name,
@@ -13,7 +17,8 @@ SELECT format('DROP %s IF EXISTS public.%s CASCADE', obj.type, obj.name)
              WHEN 'm' THEN 'MATERIALIZED VIEW'
              WHEN 'f' THEN 'FOREIGN TABLE'
              ELSE 'TABLE'
-           END AS type
+           END AS type,
+           c.oid AS objid, 'pg_class'::regclass AS classid
       FROM pg_class c JOIN pg_namespace n ON n.oid = c.relnamespace
      WHERE n.nspname = 'public' AND c.relkind IN ('r', 'p', 'v', 'm', 'f')
        AND pg_get_userbyid(c.relowner) = current_user
@@ -21,17 +26,20 @@ SELECT format('DROP %s IF EXISTS public.%s CASCADE', obj.type, obj.name)
     -- Overloaded functions share a proname; DROP needs the identity
     -- signature or psql aborts with "function name is not unique".
     SELECT format('%I(%s)', p.proname, pg_get_function_identity_arguments(p.oid)) AS name,
-           CASE p.prokind WHEN 'p' THEN 'PROCEDURE' ELSE 'FUNCTION' END AS type
+           CASE p.prokind WHEN 'p' THEN 'PROCEDURE' ELSE 'FUNCTION' END AS type,
+           p.oid AS objid, 'pg_proc'::regclass AS classid
       FROM pg_proc p JOIN pg_namespace n ON n.oid = p.pronamespace
      WHERE n.nspname = 'public' AND p.prokind IN ('f', 'p', 'w')
        AND pg_get_userbyid(p.proowner) = current_user
     UNION ALL
-    SELECT format('%I', c.relname) AS name, 'SEQUENCE' AS type
+    SELECT format('%I', c.relname) AS name, 'SEQUENCE' AS type,
+           c.oid AS objid, 'pg_class'::regclass AS classid
       FROM pg_class c JOIN pg_namespace n ON n.oid = c.relnamespace
      WHERE n.nspname = 'public' AND c.relkind = 'S'
        AND pg_get_userbyid(c.relowner) = current_user
     UNION ALL
-    SELECT format('%I', t.typname) AS name, 'TYPE' AS type
+    SELECT format('%I', t.typname) AS name, 'TYPE' AS type,
+           t.oid AS objid, 'pg_type'::regclass AS classid
       FROM pg_type t JOIN pg_namespace n ON n.oid = t.typnamespace
      WHERE n.nspname = 'public'
        AND pg_get_userbyid(t.typowner) = current_user
@@ -40,25 +48,36 @@ SELECT format('DROP %s IF EXISTS public.%s CASCADE', obj.type, obj.name)
                   SELECT 1 FROM pg_class c2
                    WHERE c2.oid = t.typrelid AND c2.relkind = 'c')))
     UNION ALL
-    SELECT format('%I', col.collname) AS name, 'COLLATION' AS type
+    SELECT format('%I', col.collname) AS name, 'COLLATION' AS type,
+           col.oid AS objid, 'pg_collation'::regclass AS classid
       FROM pg_collation col JOIN pg_namespace n ON n.oid = col.collnamespace
      WHERE n.nspname = 'public'
        AND pg_get_userbyid(col.collowner) = current_user
     UNION ALL
-    SELECT format('%I', ts.cfgname) AS name, 'TEXT SEARCH CONFIGURATION' AS type
+    SELECT format('%I', ts.cfgname) AS name, 'TEXT SEARCH CONFIGURATION' AS type,
+           ts.oid AS objid, 'pg_ts_config'::regclass AS classid
       FROM pg_ts_config ts JOIN pg_namespace n ON n.oid = ts.cfgnamespace
      WHERE n.nspname = 'public'
        AND pg_get_userbyid(ts.cfgowner) = current_user
     UNION ALL
-    SELECT format('%I', d.dictname) AS name, 'TEXT SEARCH DICTIONARY' AS type
+    SELECT format('%I', d.dictname) AS name, 'TEXT SEARCH DICTIONARY' AS type,
+           d.oid AS objid, 'pg_ts_dict'::regclass AS classid
       FROM pg_ts_dict d JOIN pg_namespace n ON n.oid = d.dictnamespace
      WHERE n.nspname = 'public'
        AND pg_get_userbyid(d.dictowner) = current_user
   ) obj
+ WHERE NOT EXISTS (
+         SELECT 1 FROM pg_depend dep
+          WHERE dep.classid = obj.classid AND dep.objid = obj.objid
+            AND dep.deptype = 'e')
 UNION ALL
 SELECT format('DROP SCHEMA IF EXISTS %I CASCADE', n.nspname)
   FROM pg_namespace n
  WHERE NOT starts_with(n.nspname, 'pg_')
    AND n.nspname NOT IN ('public', 'information_schema')
    AND pg_get_userbyid(n.nspowner) = current_user
+   AND NOT EXISTS (
+         SELECT 1 FROM pg_depend dep
+          WHERE dep.classid = 'pg_namespace'::regclass AND dep.objid = n.oid
+            AND dep.deptype = 'e')
 \gexec

src/baudolo/restore/files.py

@@ -59,6 +59,6 @@ def restore_volume_files(volume_name: str, backup_files_dir: str) -> int:
     # rsync reads "dir/" as its contents and "dir" as the directory itself.
     src = f"{Path(backup_files_dir)}{os.sep}"
     dest = f"{Path(mountpoint)}{os.sep}"
-    run(["rsync", "-avv", "--delete", src, dest])
+    run(["rsync", "-aHAX", "-vv", "--delete", src, dest])
     print("File restore complete.")
     return 0

tests/e2e/helpers/fixtures.py

@@ -25,7 +25,7 @@ def backup_run(
     images_no_stop_required: list[str],
     images_no_backup_required: list[str] | None = None,
     only_sql: bool = False,
-) -> None:
+) -> subprocess.CompletedProcess:
     cmd = [
         "baudolo",
         "--compose-dir",
@@ -49,7 +49,7 @@ def backup_run(
         cmd += ["--only-sql"]
 
     try:
-        run(cmd, capture=True, check=True)
+        return run(cmd, capture=True, check=True)
     except subprocess.CalledProcessError as e:
         print(">>> baudolo failed (exit code:", e.returncode, ")")
         if e.stdout:

tests/e2e/helpers/process.py

@@ -96,12 +96,13 @@ def wait_for_mariadb(
     container: str, *, root_password: str, timeout_s: int = 90
 ) -> None:
     """
-    Liveness probe for MariaDB.
+    Readiness probe for MariaDB, as root over the socket.
 
-    IMPORTANT (MariaDB 11):
-    Root TCP auth is often restricted (unix_socket auth), so a TCP ping like
-    `mariadb-admin -uroot -p... -h localhost ping` can fail even though the server is up.
-    We therefore check readiness via a socket-based query.
+    The entrypoint drops root@127.0.0.1, so root is socket-only, and it
+    installs root@localhost without unix_socket auth: a probe without the
+    password only passes in the init window before the password is set.
+    `@@skip_networking` must be 0 so the entrypoint's temporary server,
+    which shuts down right after init, does not count as ready.
     """
     deadline = time.time() + timeout_s
     while time.time() < deadline:
@@ -112,12 +113,15 @@ def wait_for_mariadb(
                 container,
                 "sh",
                 "-lc",
-                'mariadb -uroot --protocol=socket -e "SELECT 1;"',
+                (
+                    f"mariadb -uroot -p{root_password} --protocol=socket "
+                    '-N -e "SELECT @@skip_networking;"'
+                ),
             ],
             capture=True,
             check=False,
         )
-        if p.returncode == 0:
+        if p.returncode == 0 and p.stdout.strip() == "0":
             return
         time.sleep(1)
     raise TimeoutError(

tests/e2e/test_e2e_app_container_ships_client_tools.py

@@ -0,0 +1,184 @@
+"""An application container that ships the engine's client tools.
+
+This is the shape a dedicated database deploys in: the engine runs as
+`<app>-database` while the application itself runs as `<app>`, and neither is
+declared through --database-containers, so both names go through the instance
+regex. `<app>-database` loses its suffix and lands on the instance `<app>` -
+and `<app>` carries no database token at all, so a fallback that returns the
+name unchanged lands on that same instance and offers the application container
+as a second engine for the same row.
+
+Discourse is the live example: its application container is named `discourse`
+by its own launcher and ships pg_dumpall, so a dump command starts there and
+writes a file that looks like a backup and holds none of the data.
+"""
+
+import json
+import unittest
+from pathlib import Path
+
+from baudolo.generation import DUMP_SUFFIX, FILES_DIR, MANIFEST_FILE, SQL_DIR
+
+from .helpers import (
+    POSTGRES_DATA_DIR,
+    POSTGRES_IMAGE,
+    backup_path,
+    backup_run,
+    cleanup_docker,
+    create_minimal_compose_dir,
+    ensure_empty_dir,
+    latest_version_dir,
+    require_docker,
+    run,
+    unique,
+    wait_for_postgres,
+    write_databases_csv,
+)
+
+MARKER = "the-application-volume-holds-files"
+PAYLOAD = "shop-payload"
+
+
+class TestE2EAppContainerShipsClientTools(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls) -> None:
+        require_docker()
+        # uuid4 hex may begin with "db", which the instance regex would split
+        # on and turn the application container into a different instance,
+        # hiding exactly the collision this module is about.
+        cls.prefix = unique("baudolo-e2e-app-tools").replace("-db", "-xb")
+        cls.backups_dir = f"/tmp/{cls.prefix}/Backups"
+        ensure_empty_dir(cls.backups_dir)
+        cls.compose_dir = create_minimal_compose_dir(f"/tmp/{cls.prefix}")
+        cls.repo_name = cls.prefix
+
+        cls.engine = f"{cls.prefix}-shop-database"
+        cls.app = f"{cls.prefix}-shop"
+        cls.engine_volume = f"{cls.prefix}-shop-database-vol"
+        cls.app_volume = f"{cls.prefix}-shop-app-vol"
+        cls.containers = [cls.engine, cls.app]
+        cls.volumes = [cls.engine_volume, cls.app_volume]
+
+        run(["docker", "volume", "create", cls.engine_volume])
+        run(["docker", "volume", "create", cls.app_volume])
+
+        run(
+            [
+                "docker",
+                "run",
+                "-d",
+                "--name",
+                cls.engine,
+                "-e",
+                "POSTGRES_PASSWORD=shoppw",
+                "-e",
+                "POSTGRES_DB=shopdb",
+                "-e",
+                "POSTGRES_USER=postgres",
+                "-v",
+                f"{cls.engine_volume}:{POSTGRES_DATA_DIR}",
+                POSTGRES_IMAGE,
+            ]
+        )
+
+        run(
+            [
+                "docker",
+                "run",
+                "-d",
+                "--name",
+                cls.app,
+                "--entrypoint",
+                "sh",
+                "-v",
+                f"{cls.app_volume}:/data",
+                POSTGRES_IMAGE,
+                "-c",
+                f"echo '{MARKER}' > /data/marker.txt && sleep 3600",
+            ]
+        )
+
+        wait_for_postgres(cls.engine, user="postgres", timeout_s=90)
+        run(
+            [
+                "docker",
+                "exec",
+                cls.engine,
+                "sh",
+                "-lc",
+                (
+                    'psql -U postgres -d shopdb -c "CREATE TABLE orders (id int, '
+                    f"note text); INSERT INTO orders VALUES (1,'{PAYLOAD}');\""
+                ),
+            ],
+            check=True,
+        )
+
+        cls.databases_csv = f"/tmp/{cls.prefix}/databases.csv"
+        write_databases_csv(
+            cls.databases_csv,
+            [(cls.app, "shopdb", "postgres", "shoppw")],
+        )
+
+        backup_run(
+            backups_dir=cls.backups_dir,
+            repo_name=cls.repo_name,
+            compose_dir=cls.compose_dir,
+            databases_csv=cls.databases_csv,
+            database_containers=["dummy-db"],
+            images_no_stop_required=[POSTGRES_IMAGE],
+        )
+        cls.hash, cls.version = latest_version_dir(cls.backups_dir, cls.repo_name)
+
+    @classmethod
+    def tearDownClass(cls) -> None:
+        cleanup_docker(containers=cls.containers, volumes=cls.volumes)
+
+    def volume_dir(self, volume: str) -> Path:
+        return backup_path(self.backups_dir, self.repo_name, self.version, volume)
+
+    def test_the_engine_volume_was_dumped(self) -> None:
+        dump = self.volume_dir(self.engine_volume) / SQL_DIR / f"shopdb{DUMP_SUFFIX}"
+        self.assertTrue(dump.is_file(), f"expected a dump at {dump}")
+        self.assertIn(PAYLOAD, dump.read_text(encoding="utf-8"))
+
+    def test_the_application_volume_produced_no_dump(self) -> None:
+        """The collision this module exists for: the application container
+        answers the same instance as the engine and starts a dump of its own."""
+        sql_dir = self.volume_dir(self.app_volume) / SQL_DIR
+        self.assertFalse(
+            sql_dir.exists(),
+            f"the application container was dumped: {sorted(sql_dir.iterdir())}"
+            if sql_dir.exists()
+            else "",
+        )
+
+    def test_the_application_volume_was_backed_up_as_files(self) -> None:
+        """Refusing the dump must not cost the volume its backup."""
+        marker = self.volume_dir(self.app_volume) / FILES_DIR / "marker.txt"
+        self.assertTrue(marker.is_file(), f"expected a file backup at {marker}")
+        self.assertIn(MARKER, marker.read_text(encoding="utf-8"))
+
+    def test_the_manifest_does_not_call_the_application_volume_a_database(self) -> None:
+        manifest = json.loads(
+            (self.volume_dir(self.app_volume).parent / MANIFEST_FILE).read_text(
+                encoding="utf-8"
+            )
+        )
+        entry = manifest["volumes"][self.app_volume]
+        self.assertFalse(entry["database"], entry)
+        self.assertFalse(entry["dumped"], entry)
+
+    def test_the_manifest_records_the_engine_volume_as_dumped(self) -> None:
+        manifest = json.loads(
+            (self.volume_dir(self.engine_volume).parent / MANIFEST_FILE).read_text(
+                encoding="utf-8"
+            )
+        )
+        entry = manifest["volumes"][self.engine_volume]
+        self.assertTrue(entry["database"], entry)
+        self.assertTrue(entry["dumped"], entry)
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/e2e/test_e2e_files_live_writer_precopy.py

@@ -0,0 +1,110 @@
+"""A writer that shrinks files mid-read fails the live pre-copy, not the run."""
+
+import unittest
+
+from .helpers import (
+    backup_path,
+    backup_run,
+    cleanup_docker,
+    create_minimal_compose_dir,
+    ensure_empty_dir,
+    latest_version_dir,
+    require_docker,
+    run,
+    unique,
+    wait_for_log,
+    write_databases_csv,
+)
+
+CHURN_FILES = 8
+
+WRITER = f"""
+trap 'exit 0' TERM
+echo hello > /data/hello.txt
+for i in $(seq 1 {CHURN_FILES}); do
+  (while :; do truncate -s 0 /data/churn$i; truncate -s 16M /data/churn$i; done) &
+done
+echo ready
+wait
+"""
+
+
+class TestE2EFilesLiveWriterPreCopy(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls) -> None:
+        require_docker()
+        cls.prefix = unique("baudolo-e2e-live-writer")
+        cls.backups_dir = f"/tmp/{cls.prefix}/Backups"
+        ensure_empty_dir(cls.backups_dir)
+
+        cls.compose_dir = create_minimal_compose_dir(f"/tmp/{cls.prefix}")
+        cls.repo_name = cls.prefix
+
+        cls.volume = f"{cls.prefix}-vol"
+        cls.writer = f"{cls.prefix}-writer"
+        cls.containers = [cls.writer]
+        cls.volumes = [cls.volume]
+
+        run(["docker", "volume", "create", cls.volume])
+        run(
+            [
+                "docker",
+                "run",
+                "-d",
+                "--name",
+                cls.writer,
+                "-v",
+                f"{cls.volume}:/data",
+                "alpine:3.20",
+                "sh",
+                "-c",
+                WRITER,
+            ]
+        )
+        wait_for_log(cls.writer, "ready")
+
+        cls.databases_csv = f"/tmp/{cls.prefix}/databases.csv"
+        write_databases_csv(cls.databases_csv, [])
+
+        cls.result = backup_run(
+            backups_dir=cls.backups_dir,
+            repo_name=cls.repo_name,
+            compose_dir=cls.compose_dir,
+            databases_csv=cls.databases_csv,
+            database_containers=["dummy-db"],
+            images_no_stop_required=["dummy-image"],
+        )
+
+        cls.hash, cls.version = latest_version_dir(cls.backups_dir, cls.repo_name)
+
+    @classmethod
+    def tearDownClass(cls) -> None:
+        cleanup_docker(containers=cls.containers, volumes=cls.volumes)
+
+    def test_the_live_pre_copy_hit_the_writer(self) -> None:
+        self.assertIn(
+            f"WARNING: live pre-copy of volume '{self.volume}' failed",
+            self.result.stdout,
+            "the writer never shrank a file under rsync, so this run proves nothing",
+        )
+
+    def test_the_stopped_copy_captured_the_volume(self) -> None:
+        files = (
+            backup_path(self.backups_dir, self.repo_name, self.version, self.volume)
+            / "files"
+        )
+        self.assertEqual((files / "hello.txt").read_text().strip(), "hello")
+        self.assertEqual(
+            sorted(p.name for p in files.glob("churn*")),
+            sorted(f"churn{i}" for i in range(1, CHURN_FILES + 1)),
+        )
+
+    def test_the_writer_runs_again_after_the_backup(self) -> None:
+        state = run(
+            ["docker", "inspect", "-f", "{{.State.Running}}", self.writer]
+        ).stdout.strip()
+        self.assertEqual(state, "true")
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/e2e/test_e2e_mariadb_anonymous_preemption.py

@@ -100,7 +100,10 @@ class TestE2EMariaDBAnonymousPreemption(unittest.TestCase):
                 cls.db_container,
                 "sh",
                 "-lc",
-                f'mariadb -uroot --protocol=socket -e "{bootstrap_sql}"',
+                (
+                    f"mariadb -uroot -p{cls.root_password} --protocol=socket "
+                    f'-e "{bootstrap_sql}"'
+                ),
             ]
         )
 

tests/e2e/test_e2e_postgres_empty_drop_hard.py

@@ -24,6 +24,7 @@ from .helpers import (
 # is not unique") and english_stem_nostop reproduces taiga's text search
 # dictionary abort (duplicate pg_ts_dict_dictname_index).
 SCENARIO_SQL = (
+    "CREATE EXTENSION pg_trgm;"
     "CREATE SCHEMA discourse_functions;"
     "CREATE TABLE discourse_functions.helper (id int);"
     "INSERT INTO discourse_functions.helper VALUES (1);"
@@ -166,6 +167,13 @@ class TestE2EPostgresEmptyDropHard(unittest.TestCase):
         )
         self.assertEqual(self._scalar("SELECT public.f(41) + public.f();"), "42")
 
+    def test_the_extension_survived_the_preclean(self) -> None:
+        self.assertEqual(
+            self._scalar("SELECT count(*) FROM pg_extension WHERE extname='pg_trgm';"),
+            "1",
+        )
+        self.assertEqual(self._scalar("SELECT similarity('abc','abc')::int;"), "1")
+
     def test_text_search_dictionary_restored_once(self) -> None:
         self.assertEqual(
             self._scalar(

tests/e2e/test_e2e_postgres_password_required.py

@@ -0,0 +1,159 @@
+"""An engine whose loopback auth really demands a password.
+
+Every other Postgres scenario runs stock postgres:alpine, whose generated
+pg_hba grants trust on 127.0.0.1 and ::1 - so `pg_dump -h localhost` never
+needs the password and a dump succeeds whether or not baudolo hands one to the
+container. This module makes the password mandatory, which is what a dedicated
+engine on a real host does.
+"""
+
+import unittest
+from pathlib import Path
+
+from baudolo.generation import CLUSTER_SUFFIX, DUMP_SUFFIX, FILES_DIR, SQL_DIR
+
+from .helpers import (
+    POSTGRES_DATA_DIR,
+    POSTGRES_IMAGE,
+    backup_path,
+    backup_run,
+    cleanup_docker,
+    create_minimal_compose_dir,
+    ensure_empty_dir,
+    latest_version_dir,
+    require_docker,
+    run,
+    unique,
+    wait_for_postgres,
+    write_databases_csv,
+)
+
+
+class TestE2EPostgresPasswordRequired(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls) -> None:
+        require_docker()
+        cls.prefix = unique("baudolo-e2e-pg-password-required")
+        cls.backups_dir = f"/tmp/{cls.prefix}/Backups"
+        ensure_empty_dir(cls.backups_dir)
+        cls.compose_dir = create_minimal_compose_dir(f"/tmp/{cls.prefix}")
+        cls.repo_name = cls.prefix
+
+        cls.pg_container = f"{cls.prefix}-pg"
+        cls.pg_volume = f"{cls.prefix}-pg-vol"
+        cls.containers = [cls.pg_container]
+        cls.volumes = [cls.pg_volume]
+
+        run(["docker", "volume", "create", cls.pg_volume])
+        run(
+            [
+                "docker",
+                "run",
+                "-d",
+                "--name",
+                cls.pg_container,
+                "-e",
+                "POSTGRES_PASSWORD=pgpw",
+                "-e",
+                "POSTGRES_DB=appdb",
+                "-e",
+                "POSTGRES_USER=postgres",
+                # The entrypoint evals this into its initdb call, so the host
+                # lines of pg_hba demand scram while the local socket stays
+                # trust - the entrypoint's own init and the seeding below keep
+                # working, and only a TCP connection needs the password.
+                "-e",
+                "POSTGRES_INITDB_ARGS=--auth-host=scram-sha-256",
+                "-v",
+                f"{cls.pg_volume}:{POSTGRES_DATA_DIR}",
+                POSTGRES_IMAGE,
+            ]
+        )
+        wait_for_postgres(cls.pg_container, user="postgres", timeout_s=90)
+
+        run(
+            [
+                "docker",
+                "exec",
+                cls.pg_container,
+                "sh",
+                "-lc",
+                (
+                    'psql -U postgres -d appdb -c "CREATE TABLE t (id int primary '
+                    "key, v text); INSERT INTO t VALUES (1,'ok');\""
+                ),
+            ],
+            check=True,
+        )
+
+        cls.unauthenticated = run(
+            [
+                "docker",
+                "exec",
+                cls.pg_container,
+                "sh",
+                "-lc",
+                "pg_dump -U postgres -d appdb -h localhost",
+            ],
+            capture=True,
+            check=False,
+        )
+
+        cls.databases_csv = f"/tmp/{cls.prefix}/databases.csv"
+        write_databases_csv(
+            cls.databases_csv,
+            [
+                (cls.pg_container, "appdb", "postgres", "pgpw"),
+                (cls.pg_container, "*", "postgres", "pgpw"),
+            ],
+        )
+
+        backup_run(
+            backups_dir=cls.backups_dir,
+            repo_name=cls.repo_name,
+            compose_dir=cls.compose_dir,
+            databases_csv=cls.databases_csv,
+            database_containers=[cls.pg_container],
+            images_no_stop_required=[POSTGRES_IMAGE],
+            only_sql=True,
+        )
+        cls.hash, cls.version = latest_version_dir(cls.backups_dir, cls.repo_name)
+
+    @classmethod
+    def tearDownClass(cls) -> None:
+        cleanup_docker(containers=cls.containers, volumes=cls.volumes)
+
+    def volume_dir(self) -> Path:
+        return backup_path(
+            self.backups_dir, self.repo_name, self.version, self.pg_volume
+        )
+
+    def test_a_dump_without_the_password_is_refused_by_the_server(self) -> None:
+        """Without this the module is vacuous: a pg_hba still saying trust would
+        let a baudolo that forwards nothing pass just as well."""
+        self.assertNotEqual(self.unauthenticated.returncode, 0)
+        self.assertIn("no password supplied", self.unauthenticated.stderr or "")
+
+    def test_the_configured_database_was_dumped(self) -> None:
+        dump = self.volume_dir() / SQL_DIR / f"appdb{DUMP_SUFFIX}"
+        self.assertTrue(dump.is_file(), f"expected a dump at {dump}")
+        self.assertIn("Dumped by pg_dump", dump.read_text(encoding="utf-8"))
+
+    def test_the_dump_carries_the_payload(self) -> None:
+        """pg_dump emits table data as COPY ... FROM stdin, so the row reads as
+        tab-separated values rather than as an INSERT literal."""
+        dump = self.volume_dir() / SQL_DIR / f"appdb{DUMP_SUFFIX}"
+        self.assertIn("COPY public.t (id, v) FROM stdin;", dump.read_text("utf-8"))
+        self.assertIn("1\tok", dump.read_text(encoding="utf-8"))
+
+    def test_the_cluster_row_was_dumped_too(self) -> None:
+        cluster = self.volume_dir() / SQL_DIR / f"{self.pg_container}{CLUSTER_SUFFIX}"
+        self.assertTrue(cluster.is_file(), f"expected a cluster dump at {cluster}")
+        self.assertIn("CREATE DATABASE", cluster.read_text(encoding="utf-8"))
+
+    def test_only_sql_left_no_file_copy_behind(self) -> None:
+        self.assertFalse((self.volume_dir() / FILES_DIR).exists())
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/e2e/test_e2e_snapshot.py

@@ -36,9 +36,14 @@ ZFS_READY = "{ [ -c /dev/zfs ] || modprobe zfs 2>/dev/null; }; [ -c /dev/zfs ]"
 def mount_script(fstype: str) -> str:
     """Build a filesystem on a loop device and carve out the snapshot subject."""
     if fstype == "zfs":
+        # Exception: a loop device, not the /img file, because the kernel opens
+        # vdevs from a taskq thread that resolves paths in the host's root.
+        # The pool is kernel-wide, so it is destroyed on exit, but only once
+        # this script created it.
         return (
-            f"{PACKAGES} && {ZFS_READY} && truncate -s 400M /img "
-            "&& zpool create -m none baudolo /img "
+            f"{PACKAGES} && {ZFS_READY} && truncate -s 400M /img && {ATTACH} "
+            '&& zpool create -m none baudolo "$LOOP" '
+            "&& trap 'zpool destroy -f baudolo; losetup -d \"$LOOP\"' EXIT "
             "&& zfs create -o mountpoint=/subject/docker baudolo/docker"
         )
     return (

tests/unit/backup/test_app_live_precopy.py

@@ -0,0 +1,70 @@
+"""Contract of app.main's live copy when no snapshot is taken."""
+
+from __future__ import annotations
+
+import unittest
+from unittest import mock
+
+from baudolo.backup import app
+from baudolo.backup.shell import BackupError
+from baudolo.backup.volume import Backing
+
+from . import BASE_ARGV
+
+
+def drive(*, stop: bool, fail_live: bool) -> list[str]:
+    events: list[str] = []
+
+    def record(versions_dir, volume_name, volume_dir, *, authoritative, source):
+        events.append("authoritative" if authoritative else "live")
+        if fail_live and not authoritative:
+            raise BackupError("rsync exit code 23")
+
+    with (
+        mock.patch("sys.argv", BASE_ARGV),
+        mock.patch.object(app, "get_machine_id", return_value="machine"),
+        mock.patch.object(app, "create_version_directory", return_value="/gen"),
+        mock.patch.object(app, "create_volume_directory", return_value="/gen/vol"),
+        mock.patch.object(app, "load_databases_df", return_value=None),
+        mock.patch.object(app, "docker_volume_names", return_value=["vol"]),
+        mock.patch.object(app, "containers_using_volume", return_value=["c"]),
+        mock.patch.object(app, "volume_is_fully_ignored", return_value=False),
+        mock.patch.object(app, "backup_dumps_for_volume", return_value=(False, False)),
+        mock.patch.object(
+            app,
+            "inspect_backing",
+            return_value=Backing("/var/lib/docker/volumes/vol/_data"),
+        ),
+        mock.patch.object(app, "requires_stop", return_value=stop),
+        mock.patch.object(app, "filter_stoppable", return_value=["c"]),
+        mock.patch.object(
+            app,
+            "change_containers_status",
+            side_effect=lambda containers, status: events.append(status),
+        ),
+        mock.patch.object(app, "write_manifest"),
+        mock.patch.object(app, "stamp_directory"),
+        mock.patch.object(app, "handle_docker_compose_services"),
+        mock.patch.object(app, "backup_volume", side_effect=record),
+    ):
+        app.main()
+    return events
+
+
+class TestLivePreCopy(unittest.TestCase):
+    def test_a_failed_pre_copy_is_replaced_by_the_stopped_copy(self) -> None:
+        self.assertEqual(
+            drive(stop=True, fail_live=True),
+            ["live", "stop", "authoritative", "start"],
+        )
+
+    def test_a_failed_live_copy_without_a_stop_aborts_the_run(self) -> None:
+        with self.assertRaises(BackupError):
+            drive(stop=False, fail_live=True)
+
+    def test_a_volume_without_a_stop_is_copied_live_once(self) -> None:
+        self.assertEqual(drive(stop=False, fail_live=False), ["live"])
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/unit/backup/test_docker_exec_env.py

@@ -0,0 +1,61 @@
+"""How a secret reaches the command running inside the container."""
+
+from __future__ import annotations
+
+import unittest
+
+from baudolo.backup.db import fallback_pg_dumpall
+from baudolo.backup.docker import docker_exec_argv
+
+
+class TestForwardEnv(unittest.TestCase):
+    def test_nothing_is_added_when_no_variable_is_named(self) -> None:
+        self.assertEqual(
+            docker_exec_argv("c1", ["true"]),
+            ["docker", "exec", "c1", "true"],
+        )
+
+    def test_a_named_variable_is_forwarded_without_its_value(self) -> None:
+        """-e NAME=value would publish the secret in the host's process list."""
+        argv = docker_exec_argv("c1", ["true"], forward_env=["PGPASSWORD"])
+        self.assertEqual(argv, ["docker", "exec", "-e", "PGPASSWORD", "c1", "true"])
+
+    def test_the_flag_precedes_the_container(self) -> None:
+        """docker reads options before the container name, arguments after it."""
+        argv = docker_exec_argv(
+            "c1", ["pg_dump", "-U", "u"], interactive=True, forward_env=["PGPASSWORD"]
+        )
+        self.assertLess(argv.index("-e"), argv.index("c1"))
+        self.assertLess(argv.index("-i"), argv.index("c1"))
+        self.assertGreater(argv.index("pg_dump"), argv.index("c1"))
+
+    def test_several_variables_each_get_their_own_flag(self) -> None:
+        argv = docker_exec_argv("c1", ["true"], forward_env=["A", "B"])
+        self.assertEqual(argv[:6], ["docker", "exec", "-e", "A", "-e", "B"])
+
+
+class TestPostgresDumpCarriesThePassword(unittest.TestCase):
+    def test_the_cluster_dump_forwards_pgpassword(self) -> None:
+        seen: dict = {}
+
+        def fake(command, out_file, *, env=None):
+            seen["command"] = command
+            seen["env"] = env
+
+        import baudolo.backup.db as db
+
+        original = db.execute_to_file
+        db.execute_to_file = fake
+        try:
+            fallback_pg_dumpall("pg", "user", "secret", "/tmp/out.sql")
+        finally:
+            db.execute_to_file = original
+
+        self.assertIn("-e", seen["command"])
+        self.assertEqual(seen["command"][seen["command"].index("-e") + 1], "PGPASSWORD")
+        self.assertEqual(seen["env"], {"PGPASSWORD": "secret"})
+        self.assertNotIn("secret", seen["command"])
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/unit/backup/test_get_instance.py

@@ -0,0 +1,80 @@
+"""Which databases.csv instance a container name resolves to.
+
+The cases are the container names real deployments produce, in both compose
+and swarm, so a change to the regex has to state which shape it gives up.
+"""
+
+from __future__ import annotations
+
+import unittest
+
+from baudolo.backup.db import get_instance
+
+
+class TestDeclaredContainers(unittest.TestCase):
+    def test_a_declared_container_is_its_own_instance(self) -> None:
+        self.assertEqual(
+            get_instance("postgres-central", ["postgres-central"]), "postgres-central"
+        )
+
+    def test_a_declaration_beats_the_regex(self) -> None:
+        """A declared name is taken whole even when it carries a token the
+        fallback would otherwise strip."""
+        self.assertEqual(
+            get_instance("shop-database", ["shop-database"]), "shop-database"
+        )
+
+    def test_a_qualified_central_name_still_has_to_be_declared(self) -> None:
+        self.assertIsNone(get_instance("postgres-central", []))
+
+
+class TestContainersNamedAfterTheirEngine(unittest.TestCase):
+    def test_a_bare_engine_name_is_its_own_instance(self) -> None:
+        for name in ("postgres", "mariadb", "mysql", "db", "database"):
+            with self.subTest(container=name):
+                self.assertEqual(get_instance(name, []), name)
+
+    def test_a_swarm_task_of_such_a_container_keeps_the_instance(self) -> None:
+        self.assertEqual(get_instance("postgres_postgres.1.k3f9x2", []), "postgres")
+        self.assertEqual(get_instance("mariadb_mariadb.1.k3f9x2", []), "mariadb")
+
+
+class TestDedicatedEngines(unittest.TestCase):
+    def test_compose_names_the_container_with_a_hyphen(self) -> None:
+        self.assertEqual(get_instance("discourse-database", []), "discourse")
+
+    def test_swarm_names_the_task_with_an_underscore_and_a_slot(self) -> None:
+        """Swarm suppresses container_name and names the task
+        <stack>_<service>.<slot>.<id>, which must land on the same instance as
+        the compose name so one databases.csv serves both modes."""
+        self.assertEqual(get_instance("discourse_database.1.k3f9x2", []), "discourse")
+
+    def test_an_explicitly_named_engine_keeps_its_entity(self) -> None:
+        self.assertEqual(get_instance("bigbluebutton-postgres-1", []), "bigbluebutton")
+
+    def test_the_short_token_is_stripped_too(self) -> None:
+        self.assertEqual(get_instance("matomo-db", []), "matomo")
+
+    def test_mariadb_uses_the_same_suffix(self) -> None:
+        self.assertEqual(get_instance("matomo-database", []), "matomo")
+
+    def test_an_engine_named_suffix_is_stripped_too(self) -> None:
+        self.assertEqual(get_instance("shop-mariadb", []), "shop")
+        self.assertEqual(get_instance("shop-mysql", []), "shop")
+
+
+class TestApplicationContainers(unittest.TestCase):
+    def test_a_bare_application_name_is_not_a_database(self) -> None:
+        """Returning the name unchanged here would offer the application as a
+        second engine for its own dedicated database's instance."""
+        self.assertIsNone(get_instance("discourse", []))
+
+    def test_a_swarm_application_task_is_not_a_database(self) -> None:
+        self.assertIsNone(get_instance("discourse_discourse.1.k3f9x2", []))
+
+    def test_an_application_that_merely_starts_with_a_token_is_not_split(self) -> None:
+        self.assertIsNone(get_instance("dbeaver", []))
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/unit/backup/test_snapshot.py

@@ -21,6 +21,14 @@ class Runner:
         return []
 
 
+class Unmountable(Runner):
+    def __call__(self, command: list[str]) -> list[str]:
+        result = super().__call__(command)
+        if command[0] == "mount":
+            raise BackupError("permission denied")
+        return result
+
+
 class TestBtrfs(unittest.TestCase):
     def test_it_creates_a_read_only_snapshot_inside_the_subject(self) -> None:
         run = Runner()
@@ -95,12 +103,55 @@ class TestZfs(unittest.TestCase):
             run.calls[-1], ["zfs", "destroy", "tank/docker@baudolo-20260731"]
         )
 
-    def test_it_maps_a_volume_path_through_the_dot_zfs_directory(self) -> None:
+    def test_it_mounts_the_snapshot_inside_the_subject(self) -> None:
+        run = self._run()
+        with volume_snapshot("zfs", "/var/lib/docker", "20260731", run=run):
+            pass
+        self.assertIn(
+            [
+                "mount",
+                "-t",
+                "zfs",
+                "tank/docker@baudolo-20260731",
+                "/var/lib/docker/.baudolo-20260731",
+            ],
+            run.calls,
+        )
+
+    def test_it_maps_a_volume_path_into_the_mounted_snapshot(self) -> None:
         run = self._run()
         with volume_snapshot("zfs", "/var/lib/docker", "20260731", run=run) as resolve:
             self.assertEqual(
                 resolve("/var/lib/docker/volumes/postgres_data/_data"),
-                "/var/lib/docker/.zfs/snapshot/baudolo-20260731/volumes/postgres_data/_data",
+                "/var/lib/docker/.baudolo-20260731/volumes/postgres_data/_data",
+            )
+
+    def test_it_unmounts_before_it_destroys(self) -> None:
+        run = self._run()
+        with volume_snapshot("zfs", "/var/lib/docker", "20260731", run=run):
+            pass
+        self.assertEqual(
+            run.calls[-3:],
+            [
+                ["umount", "/var/lib/docker/.baudolo-20260731"],
+                ["rmdir", "/var/lib/docker/.baudolo-20260731"],
+                ["zfs", "destroy", "tank/docker@baudolo-20260731"],
+            ],
+        )
+
+    def test_a_failed_mount_leaves_no_snapshot_behind(self) -> None:
+        run = Unmountable({"zfs list": ["tank/docker"]})
+        with (
+            self.assertRaises(BackupError),
+            volume_snapshot("zfs", "/var/lib/docker", "20260731", run=run),
+        ):
+            pass
+        self.assertEqual(
+            run.calls[-2:],
+            [
+                ["rmdir", "/var/lib/docker/.baudolo-20260731"],
+                ["zfs", "destroy", "tank/docker@baudolo-20260731"],
+            ],
         )
 
     def test_an_unmounted_dataset_is_an_error(self) -> None:

tests/unit/backup/test_volume.py

@@ -46,9 +46,12 @@ class TestBackupVolume(unittest.TestCase):
     def test_it_carries_no_kernel_objects_into_a_generation(self) -> None:
         self.assertIn("--no-D", self.copy())
 
+    def test_it_stores_the_metadata_a_restore_has_to_give_back(self) -> None:
+        self.assertIn("-aHAX", self.copy())
+
     def test_it_keeps_no_twin_of_what_the_second_pass_replaces(self) -> None:
         command = self.copy(authoritative=True)
-        self.assertEqual(command[:2], ["rsync", "-aP"])
+        self.assertEqual(command[:3], ["rsync", "-aHAX", "-P"])
         self.assertNotIn("--backup", command)
 
     def test_it_creates_the_destination(self) -> None: