add a few extra commands

.gitignore

@@ -1,2 +1,3 @@
 __pycache__
 *egg-info
+build/

src/pobsync/cli.py

@@ -8,7 +8,10 @@ from typing import Any
 from .commands.doctor import run_doctor
 from .commands.init_host import run_init_host
 from .commands.install import run_install
-from .errors import ConfigError, DoctorError, InstallError, PobsyncError
+from .commands.list_remotes import run_list_remotes
+from .commands.show_config import run_show_config, dump_yaml
+from .commands.run_scheduled import run_scheduled
+from .errors import ConfigError, DoctorError, InstallError, PobsyncError, LockError
 from .paths import PobsyncPaths
 from .util import is_tty, to_json_safe
 
@@ -48,6 +51,23 @@ def build_parser() -> argparse.ArgumentParser:
     dp.add_argument("--rsync-dry-run", action="store_true", help="Try rsync dry run (phase 2)")
     dp.set_defaults(_handler=cmd_doctor)
 
+    # list remotes
+    lp = sub.add_parser("list-remotes", help="List configured remotes (host configs)")
+    lp.set_defaults(_handler=cmd_list_remotes)
+
+    # show config
+    sp = sub.add_parser("show-config", help="Show host configuration (raw or effective)")
+    sp.add_argument("host", help="Host to show")
+    sp.add_argument("--effective", action="store_true", help="Show merged effective config")
+    sp.set_defaults(_handler=cmd_show_config)
+
+    # run scheduled
+    rp = sub.add_parser("run-scheduled", help="Run a scheduled backup for a host")
+    rp.add_argument("host", help="Host to back up")
+    rp.add_argument("--dry-run", action="store_true", help="Run rsync --dry-run without creating directories")
+    rp.set_defaults(_handler=cmd_run_scheduled)
+
+
     return p
 
 
@@ -79,20 +99,30 @@ def _print(result: dict[str, Any], as_json: bool) -> None:
     if as_json:
         print(json.dumps(to_json_safe(result), indent=2, sort_keys=False))
         return
-    # Minimal human output for phase 1
+
+    # Minimal human output
     if result.get("ok") is True:
         print("OK")
     else:
         print("FAILED")
+
+    # Standard action list
     if "actions" in result:
         for a in result["actions"]:
             print(f"- {a}")
+
+    # Single action (e.g. init-host)
+    if "action" in result:
+        print(f"- {result['action']}")
+
+    # Doctor-style results list
     if "results" in result:
         for r in result["results"]:
             ok = r.get("ok", False)
             label = "OK" if ok else "FAIL"
             name = r.get("check", "check")
             msg = r.get("message") or r.get("error") or ""
+
             extra = ""
             if "path" in r:
                 extra = f" ({r['path']})"
@@ -100,7 +130,23 @@ def _print(result: dict[str, Any], as_json: bool) -> None:
                 extra = f" ({r['name']})"
             elif "host" in r:
                 extra = f" ({r['host']})"
-            print(f"- {label} {name}{extra} {msg}".rstrip())
+
+            line = f"- {label} {name}{extra}"
+            if msg:
+                line += f" {msg}"
+            print(line)
+
+    # list-remotes style output
+    if "hosts" in result:
+        for h in result["hosts"]:
+            print(h)
+
+    if "snapshot" in result:
+        print(f"- snapshot {result['snapshot']}")
+
+    if "base" in result and result["base"]:
+        print(f"- base {result['base']}")
+
 
 
 def cmd_install(args: argparse.Namespace) -> int:
@@ -160,6 +206,18 @@ def cmd_init_host(args: argparse.Namespace) -> int:
     return 0 if result.get("ok") else 1
 
 
+def cmd_show_config(args: argparse.Namespace) -> int:
+    prefix = Path(args.prefix)
+    result = run_show_config(prefix=prefix, host=args.host, effective=bool(args.effective))
+
+    if args.json:
+        _print(result, as_json=True)
+    else:
+        print(dump_yaml(result["config"]).rstrip())
+
+    return 0 if result.get("ok") else 1
+
+
 def cmd_doctor(args: argparse.Namespace) -> int:
     prefix = Path(args.prefix)
     result = run_doctor(prefix=prefix, host=args.host, connect=bool(args.connect), rsync_dry_run=bool(args.rsync_dry_run))
@@ -167,6 +225,21 @@ def cmd_doctor(args: argparse.Namespace) -> int:
     return 0 if result.get("ok") else 1
 
 
+def cmd_list_remotes(args: argparse.Namespace) -> int:
+    prefix = Path(args.prefix)
+    result = run_list_remotes(prefix=prefix)
+    _print(result, as_json=bool(args.json))
+    return 0 if result.get("ok") else 1
+
+
+def cmd_run_scheduled(args: argparse.Namespace) -> int:
+    prefix = Path(args.prefix)
+    result = run_scheduled(prefix=prefix, host=args.host, dry_run=bool(args.dry_run))
+    _print(result, as_json=bool(args.json))
+    return 0 if result.get("ok") else 2
+
+
+
 def main(argv: list[str] | None = None) -> int:
     parser = build_parser()
     args = parser.parse_args(argv)
@@ -179,7 +252,10 @@ def main(argv: list[str] | None = None) -> int:
             _print({"ok": False, "error": str(e), "type": type(e).__name__}, as_json=True)
         else:
             print(f"ERROR: {e}")
+        if isinstance(e, LockError):
+            return 10
         return 1
+
     except KeyboardInterrupt:
         if args.json:
             _print({"ok": False, "error": "interrupted"}, as_json=True)

src/pobsync/commands/install.py

@@ -34,7 +34,6 @@ DEFAULT_RSYNC_ARGS = [
     "--delete-excluded",
     "--partial",
     "--partial-dir=.rsync-partial",
-    "--inplace",
     "--one-file-system",
     "--relative",
     "--human-readable",

src/pobsync/commands/list_remotes.py

@@ -0,0 +1,24 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from ..paths import PobsyncPaths
+from ..util import sanitize_host
+
+
+def run_list_remotes(prefix: Path) -> dict:
+    paths = PobsyncPaths(home=prefix)
+
+    hosts: list[str] = []
+    if paths.hosts_dir.exists():
+        for p in sorted(paths.hosts_dir.glob("*.yaml")):
+            host = p.stem
+            try:
+                sanitize_host(host)
+            except Exception:
+                # Ignore invalid filenames; doctor will catch config issues.
+                continue
+            hosts.append(host)
+
+    return {"ok": True, "hosts": hosts}
+

src/pobsync/commands/run_scheduled.py

@@ -0,0 +1,241 @@
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any
+
+import yaml
+
+from ..config.load import load_global_config, load_host_config
+from ..config.merge import build_effective_config
+from ..errors import ConfigError
+from ..lock import acquire_host_lock
+from ..paths import PobsyncPaths
+from ..rsync import build_rsync_command, build_ssh_command, run_rsync
+from ..snapshot import (
+    HostBackupDirs,
+    extract_ts_and_id_from_dirname,
+    format_iso_z,
+    generate_id,
+    list_snapshot_dirs,
+    snapshot_dir_name,
+    utc_now,
+)
+from ..util import ensure_dir, realpath_startswith, sanitize_host
+
+
+def _host_backup_dirs(backup_root: str, host: str) -> HostBackupDirs:
+    return HostBackupDirs(root=Path(backup_root) / host)
+
+
+def _find_latest_snapshot(parent: Path) -> Path | None:
+    """
+    Best-effort latest snapshot selection by timestamp in dirname.
+    Meta parsing comes later.
+    """
+    if not parent.exists():
+        return None
+
+    best: tuple[Any, Path] | None = None
+    for d in list_snapshot_dirs(parent):
+        ts, _sid = extract_ts_and_id_from_dirname(d.name)
+        if ts is None:
+            continue
+        if best is None or ts > best[0]:
+            best = (ts, d)
+    return best[1] if best else None
+
+
+def select_scheduled_base(dirs: HostBackupDirs) -> Path | None:
+    """
+    Base selection rule:
+      scheduled -> manual -> none
+    """
+    base = _find_latest_snapshot(dirs.scheduled)
+    if base is not None:
+        return base
+    return _find_latest_snapshot(dirs.manual)
+
+
+def write_meta(path: Path, data: dict[str, Any]) -> None:
+    path.write_text(yaml.safe_dump(data, sort_keys=False), encoding="utf-8")
+
+
+def run_scheduled(prefix: Path, host: str, dry_run: bool) -> dict[str, Any]:
+    host = sanitize_host(host)
+    paths = PobsyncPaths(home=prefix)
+
+    # Load and merge config
+    global_cfg = load_global_config(paths.global_config_path)
+    host_cfg = load_host_config(paths.hosts_dir / f"{host}.yaml")
+    cfg = build_effective_config(global_cfg, host_cfg)
+
+    backup_root = cfg.get("backup_root")
+    if not isinstance(backup_root, str) or not backup_root.startswith("/"):
+        raise ConfigError("Invalid backup_root in effective config")
+
+    dirs = _host_backup_dirs(backup_root, host)
+
+    # Absolute safety check
+    if not realpath_startswith(dirs.root, Path(backup_root)):
+        raise ConfigError("Refusing to operate outside backup_root")
+
+    # Base snapshot (absolute path)
+    base_dir = select_scheduled_base(dirs)
+    link_dest = str(base_dir) if base_dir else None
+
+    ssh_cfg = cfg.get("ssh", {}) or {}
+    rsync_cfg = cfg.get("rsync", {}) or {}
+
+    rsync_binary = rsync_cfg.get("binary", "rsync")
+    rsync_args = rsync_cfg.get("args_effective") or rsync_cfg.get("args") or []
+    timeout_seconds = int(rsync_cfg.get("timeout_seconds", 0) or 0)
+    bwlimit_kbps = int(rsync_cfg.get("bwlimit_kbps", 0) or 0)
+
+    source_root = cfg.get("source_root") or cfg.get("defaults", {}).get("source_root", "/")
+    if not isinstance(source_root, str) or not source_root.startswith("/"):
+        raise ConfigError("Invalid source_root in effective config")
+
+    address = cfg.get("address")
+    if not isinstance(address, str) or not address:
+        raise ConfigError("Invalid address in host config")
+
+    user = ssh_cfg.get("user") or "root"
+    source = f"{user}@{address}:{source_root}"
+
+    excludes = cfg.get("excludes_effective", []) or []
+    includes = cfg.get("includes", []) or []
+
+    ssh_cmd = build_ssh_command(ssh_cfg)
+
+    # ------------------------------------------------------------
+    # DRY RUN
+    # ------------------------------------------------------------
+    if dry_run:
+        dest = f"/tmp/pobsync-dryrun/{host}/"
+        dryrun_log = Path(f"/tmp/pobsync-dryrun/{host}/rsync.log")
+
+        cmd = build_rsync_command(
+            rsync_binary=str(rsync_binary),
+            rsync_args=list(rsync_args),
+            ssh_cmd=ssh_cmd,
+            source=source,
+            dest=dest,
+            link_dest=link_dest,
+            dry_run=True,
+            timeout_seconds=timeout_seconds,
+            bwlimit_kbps=bwlimit_kbps,
+            extra_excludes=list(excludes),
+            extra_includes=list(includes),
+        )
+
+        result = run_rsync(cmd, log_path=dryrun_log, timeout_seconds=timeout_seconds)
+
+        return {
+            "ok": result.exit_code == 0,
+            "dry_run": True,
+            "host": host,
+            "base": str(base_dir) if base_dir else None,
+            "log": str(dryrun_log),
+            "rsync": {
+                "exit_code": result.exit_code,
+                "command": result.command,
+            },
+        }
+
+    # ------------------------------------------------------------
+    # REAL RUN
+    # ------------------------------------------------------------
+    with acquire_host_lock(paths.locks_dir, host, command="run-scheduled"):
+        ts = utc_now()
+        snap_id = generate_id(8)
+        snap_name = snapshot_dir_name(ts, snap_id)
+
+        ensure_dir(dirs.root)
+        ensure_dir(dirs.scheduled)
+        ensure_dir(dirs.manual)
+        ensure_dir(dirs.incomplete)
+
+        incomplete_dir = dirs.incomplete / snap_name
+        data_dir = incomplete_dir / "data"
+        meta_dir = incomplete_dir / "meta"
+        
+        ensure_dir(data_dir)
+        ensure_dir(meta_dir)
+
+        meta_path = meta_dir / "meta.yaml"
+        log_path = meta_dir / "rsync.log"
+
+        meta: dict[str, Any] = {
+            "id": snap_id,
+            "host": host,
+            "type": "scheduled",
+            "label": None,
+            "status": "running",
+            "started_at": format_iso_z(ts),
+            "ended_at": None,
+            "base_snapshot": None,
+            "rsync": {"exit_code": None, "stats": {}},
+            "overrides": {"includes": [], "excludes": [], "base": None},
+        }
+
+        log_path.touch(exist_ok=True)
+        write_meta(meta_path, meta)
+
+        dest = str(data_dir) + "/"
+
+        cmd = build_rsync_command(
+            rsync_binary=str(rsync_binary),
+            rsync_args=list(rsync_args),
+            ssh_cmd=ssh_cmd,
+            source=source,
+            dest=dest,
+            link_dest=link_dest,
+            dry_run=False,
+            timeout_seconds=timeout_seconds,
+            bwlimit_kbps=bwlimit_kbps,
+            extra_excludes=list(excludes),
+            extra_includes=list(includes),
+        )
+
+        result = run_rsync(cmd, log_path=log_path, timeout_seconds=timeout_seconds)
+
+        end_ts = utc_now()
+        meta["ended_at"] = format_iso_z(end_ts)
+        meta["rsync"]["exit_code"] = result.exit_code
+        meta["status"] = "success" if result.exit_code == 0 else "failed"
+        write_meta(meta_path, meta)
+
+        if not log_path.exists():
+            meta["status"] = "failed"
+            meta["rsync"]["exit_code"] = 99
+            write_meta(meta_path, meta)
+            return {
+                "ok": False,
+                "dry_run": False,
+                "host": host,
+                "snapshot": str(incomplete_dir),
+                "error": "rsync.log missing after execution",
+            }
+
+        if result.exit_code != 0:
+            return {
+                "ok": False,
+                "dry_run": False,
+                "host": host,
+                "snapshot": str(incomplete_dir),
+                "status": meta["status"],
+                "rsync": {"exit_code": result.exit_code},
+            }
+
+        final_dir = dirs.scheduled / snap_name
+        incomplete_dir.rename(final_dir)
+
+        return {
+            "ok": True,
+            "dry_run": False,
+            "host": host,
+            "snapshot": str(final_dir),
+            "base": str(base_dir) if base_dir else None,
+            "rsync": {"exit_code": result.exit_code},
+        }
+

src/pobsync/commands/show_config.py

@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any
+
+import yaml
+
+from ..config.load import load_global_config, load_host_config
+from ..config.merge import build_effective_config
+from ..paths import PobsyncPaths
+from ..util import sanitize_host
+
+
+def run_show_config(prefix: Path, host: str, effective: bool) -> dict[str, Any]:
+    host = sanitize_host(host)
+    paths = PobsyncPaths(home=prefix)
+
+    global_cfg = load_global_config(paths.global_config_path)
+    host_cfg = load_host_config(paths.hosts_dir / f"{host}.yaml")
+
+    cfg = build_effective_config(global_cfg, host_cfg) if effective else host_cfg
+
+    return {
+        "ok": True,
+        "host": host,
+        "effective": effective,
+        "config": cfg,
+    }
+
+
+def dump_yaml(data: Any) -> str:
+    return yaml.safe_dump(data, sort_keys=False)
+

src/pobsync/config/schemas.py

@@ -8,6 +8,20 @@ from ..validate import FieldSpec, Schema
 HOST_RE = re.compile(r"^[A-Za-z0-9._-]+$")
 
 
+# ----------------------------
+# Shared / reusable schemas
+# ----------------------------
+
+RETENTION_SCHEMA = Schema(
+    fields={
+        "daily": FieldSpec(int, required=True, min_value=0),
+        "weekly": FieldSpec(int, required=True, min_value=0),
+        "monthly": FieldSpec(int, required=True, min_value=0),
+        "yearly": FieldSpec(int, required=True, min_value=0),
+    },
+    allow_unknown=False,
+)
+
 SSH_SCHEMA = Schema(
     fields={
         "user": FieldSpec(str, required=False),
@@ -51,11 +65,21 @@ LOGGING_SCHEMA = Schema(
 
 OUTPUT_SCHEMA = Schema(
     fields={
-        "default_format": FieldSpec(str, required=False, default="human", enum={"human", "json"}),
+        "default_format": FieldSpec(
+            str,
+            required=False,
+            default="human",
+            enum={"human", "json"},
+        ),
     },
     allow_unknown=False,
 )
 
+
+# ----------------------------
+# Global config schema
+# ----------------------------
+
 GLOBAL_SCHEMA = Schema(
     fields={
         "backup_root": FieldSpec(str, required=True),
@@ -63,22 +87,28 @@ GLOBAL_SCHEMA = Schema(
         "ssh": FieldSpec(dict, required=False, schema=SSH_SCHEMA),
         "rsync": FieldSpec(dict, required=False, schema=RSYNC_SCHEMA),
         "defaults": FieldSpec(dict, required=False, schema=DEFAULTS_SCHEMA),
-        "excludes_default": FieldSpec(list, required=False, default=[], item=FieldSpec(str)),
+        "excludes_default": FieldSpec(
+            list,
+            required=False,
+            default=[],
+            item=FieldSpec(str),
+        ),
         "logging": FieldSpec(dict, required=False, schema=LOGGING_SCHEMA),
         "output": FieldSpec(dict, required=False, schema=OUTPUT_SCHEMA),
+        # Used by `init-host` as a convenience default
+        "retention_defaults": FieldSpec(
+            dict,
+            required=False,
+            schema=RETENTION_SCHEMA,
+        ),
     },
     allow_unknown=False,
 )
 
-RETENTION_SCHEMA = Schema(
-    fields={
-        "daily": FieldSpec(int, required=True, min_value=0),
-        "weekly": FieldSpec(int, required=True, min_value=0),
-        "monthly": FieldSpec(int, required=True, min_value=0),
-        "yearly": FieldSpec(int, required=True, min_value=0),
-    },
-    allow_unknown=False,
-)
+
+# ----------------------------
+# Host config schema
+# ----------------------------
 
 HOST_RSYNC_SCHEMA = Schema(
     fields={

src/pobsync/errors.py

@@ -21,3 +21,7 @@ class InstallError(PobsyncError):
 class DoctorError(PobsyncError):
     """Raised when doctor detects fatal issues."""
 
+
+class LockError(PobsyncError):
+    """Raised when a host lock is already held by another process."""
+

src/pobsync/lock.py

@@ -0,0 +1,111 @@
+from __future__ import annotations
+
+import os
+from dataclasses import dataclass
+from datetime import datetime, timezone
+from pathlib import Path
+
+from .errors import LockError
+from .util import sanitize_host
+
+
+def _utc_now_iso() -> str:
+    return datetime.now(timezone.utc).replace(microsecond=0).isoformat().replace("+00:00", "Z")
+
+
+def _pid_is_alive(pid: int) -> bool:
+    if pid <= 0:
+        return False
+    try:
+        os.kill(pid, 0)
+    except ProcessLookupError:
+        return False
+    except PermissionError:
+        # Process exists but we might not have permission to signal it.
+        return True
+    return True
+
+
+def _read_lock_pid(lock_path: Path) -> int | None:
+    try:
+        text = lock_path.read_text(encoding="utf-8")
+    except OSError:
+        return None
+    for line in text.splitlines():
+        if line.startswith("pid:"):
+            _, val = line.split(":", 1)
+            val = val.strip()
+            try:
+                return int(val)
+            except ValueError:
+                return None
+    return None
+
+
+@dataclass
+class HostLock:
+    lock_path: Path
+
+    def release(self) -> None:
+        try:
+            self.lock_path.unlink(missing_ok=True)
+        except OSError:
+            # Best effort; leaving a stale lock is annoying but doctor can detect later.
+            pass
+
+    def __enter__(self) -> "HostLock":
+        return self
+
+    def __exit__(self, exc_type, exc, tb) -> None:
+        self.release()
+
+
+def acquire_host_lock(locks_dir: Path, host: str, command: str) -> HostLock:
+    """
+    Acquire an exclusive lock for a host. Lock path: <locks_dir>/<host>.lock
+
+    Behavior:
+      - If lock exists and PID alive: raise LockError
+      - If lock exists and PID not alive: remove lock and retry once
+    """
+    host = sanitize_host(host)
+    locks_dir.mkdir(parents=True, exist_ok=True)
+    lock_path = locks_dir / f"{host}.lock"
+
+    def _try_create() -> HostLock | None:
+        flags = os.O_WRONLY | os.O_CREAT | os.O_EXCL
+        try:
+            fd = os.open(str(lock_path), flags, 0o640)
+        except FileExistsError:
+            return None
+        try:
+            payload = (
+                f"pid: {os.getpid()}\n"
+                f"started_at: {_utc_now_iso()}\n"
+                f"command: {command}\n"
+            )
+            os.write(fd, payload.encode("utf-8"))
+        finally:
+            os.close(fd)
+        return HostLock(lock_path=lock_path)
+
+    lock = _try_create()
+    if lock is not None:
+        return lock
+
+    pid = _read_lock_pid(lock_path)
+    if pid is not None and _pid_is_alive(pid):
+        raise LockError(f"Host '{host}' is already locked by pid {pid}: {lock_path}")
+
+    # Stale lock: remove and retry once
+    try:
+        lock_path.unlink(missing_ok=True)
+    except OSError:
+        raise LockError(f"Host '{host}' lock exists but could not be removed: {lock_path}")
+
+    lock = _try_create()
+    if lock is not None:
+        return lock
+
+    raise LockError(f"Host '{host}' is already locked: {lock_path}")
+

src/pobsync/rsync.py

@@ -0,0 +1,93 @@
+from __future__ import annotations
+
+import shlex
+import subprocess
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Sequence
+
+
+@dataclass(frozen=True)
+class RsyncResult:
+    exit_code: int
+    command: list[str]
+
+
+def build_ssh_command(ssh_cfg: dict) -> list[str]:
+    cmd = ["ssh"]
+    for opt in ssh_cfg.get("options", []) or []:
+        cmd.append(str(opt))
+    port = ssh_cfg.get("port")
+    if port:
+        cmd.extend(["-p", str(port)])
+    return cmd
+
+
+def build_rsync_command(
+    *,
+    rsync_binary: str,
+    rsync_args: Sequence[str],
+    ssh_cmd: Sequence[str],
+    source: str,
+    dest: str,
+    link_dest: str | None,
+    dry_run: bool,
+    timeout_seconds: int,
+    bwlimit_kbps: int,
+    extra_excludes: Sequence[str],
+    extra_includes: Sequence[str],
+) -> list[str]:
+    cmd: list[str] = [rsync_binary]
+
+    cmd.extend(list(rsync_args))
+
+    # includes/excludes: keep it simple for now:
+    # - if includes are provided, user is responsible for correct rsync include logic.
+    # - excludes are appended as --exclude=PATTERN
+    for inc in extra_includes:
+        cmd.append(f"--include={inc}")
+    for exc in extra_excludes:
+        cmd.append(f"--exclude={exc}")
+
+    if bwlimit_kbps and bwlimit_kbps > 0:
+        cmd.append(f"--bwlimit={bwlimit_kbps}")
+
+    if dry_run:
+        cmd.append("--dry-run")
+
+    if link_dest:
+        cmd.append(f"--link-dest={link_dest}")
+
+    # ssh transport
+    cmd.extend(["-e", " ".join(shlex.quote(x) for x in ssh_cmd)])
+
+    cmd.extend([source, dest])
+    return cmd
+
+
+
+def run_rsync(command: list[str], log_path: Path, timeout_seconds: int) -> RsyncResult:
+    """
+    Run rsync and always write stdout/stderr to log_path.
+
+    This function guarantees that log_path exists after it returns,
+    unless an unrecoverable filesystem error occurred before process launch.
+    """
+    log_path.parent.mkdir(parents=True, exist_ok=True)
+    # Ensure the file exists early.
+    log_path.touch(exist_ok=True)
+
+    try:
+        with log_path.open("ab") as f:
+            p = subprocess.run(
+                command,
+                stdout=f,
+                stderr=subprocess.STDOUT,
+                timeout=timeout_seconds if timeout_seconds > 0 else None,
+            )
+        return RsyncResult(exit_code=p.returncode, command=command)
+    except subprocess.TimeoutExpired as e:
+        # Log timeout info and return a non-zero exit code.
+        with log_path.open("ab") as f:
+            f.write(b"\n[pobsync] rsync timed out\n")
+        return RsyncResult(exit_code=124, command=command)

src/pobsync/snapshot.py

@@ -0,0 +1,78 @@
+from __future__ import annotations
+
+import secrets
+import string
+from dataclasses import dataclass
+from datetime import datetime, timezone
+from pathlib import Path
+
+
+_ALPHABET = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"  # base32-ish without ambiguous chars
+
+
+def generate_id(length: int = 8) -> str:
+    return "".join(secrets.choice(_ALPHABET) for _ in range(length))
+
+
+def utc_now() -> datetime:
+    return datetime.now(timezone.utc).replace(microsecond=0)
+
+
+def format_dir_timestamp(ts: datetime) -> str:
+    # YYYYmmdd-HHMMSSZ
+    return ts.strftime("%Y%m%d-%H%M%SZ")
+
+
+def format_iso_z(ts: datetime) -> str:
+    return ts.isoformat().replace("+00:00", "Z")
+
+
+def parse_dir_timestamp(s: str) -> datetime | None:
+    # Best-effort parse for sorting; returns None if unknown.
+    try:
+        if not s.endswith("Z"):
+            return None
+        return datetime.strptime(s, "%Y%m%d-%H%M%SZ").replace(tzinfo=timezone.utc)
+    except ValueError:
+        return None
+
+
+@dataclass(frozen=True)
+class HostBackupDirs:
+    root: Path  # <backup_root>/<host>
+
+    @property
+    def scheduled(self) -> Path:
+        return self.root / "scheduled"
+
+    @property
+    def manual(self) -> Path:
+        return self.root / "manual"
+
+    @property
+    def incomplete(self) -> Path:
+        return self.root / ".incomplete"
+
+
+def snapshot_dir_name(ts: datetime, snap_id: str) -> str:
+    return f"{format_dir_timestamp(ts)}__{snap_id}"
+
+
+def list_snapshot_dirs(parent: Path) -> list[Path]:
+    if not parent.exists():
+        return []
+    dirs = [p for p in parent.iterdir() if p.is_dir()]
+    return sorted(dirs)
+
+
+def extract_ts_and_id_from_dirname(name: str) -> tuple[datetime | None, str | None]:
+    # expected: <ts>__<id> (label may exist for manual, but for base selection we only use scheduled naming)
+    if "__" not in name:
+        return None, None
+    ts_part, rest = name.split("__", 1)
+    ts = parse_dir_timestamp(ts_part)
+    snap_id = rest.split("--", 1)[0]  # strip label if present
+    if not snap_id:
+        return ts, None
+    return ts, snap_id
+

src/pobsync/util.py

@@ -18,10 +18,14 @@ def is_tty() -> bool:
 
 def sanitize_host(host: str) -> str:
     if not HOST_RE.match(host):
-        raise ValueError(f"Invalid host name: {host!r}. Allowed: [A-Za-z0-9._-]+")
+        # Import locally to avoid import cycles at module import time
+        from .errors import ConfigError
+
+        raise ConfigError(f"Invalid host name: {host!r}. Allowed: [A-Za-z0-9._-]+")
     return host
 
 
+
 def ensure_dir(path: Path, mode: int = 0o750) -> None:
     path.mkdir(parents=True, exist_ok=True)
     try: