fix an issue with link-dest pointing towards the wrong directory

README.md

@@ -1,41 +1,112 @@
 # pobsync
 
-`pobsync` is a pull-based backup tool for sysadmins.  
-It creates rsync-based snapshots with hardlinking (`--link-dest`) and stores them centrally on a backup server.
+`pobsync` is a pull-based backup tool that runs on a central backup server and pulls data from remote servers via rsync over SSH.
 
-Backups are **pulled over SSH**, not pushed, and are designed to be run from cron or manually.
+Key points:
 
----
-
-## Design overview
-
-- Runtime, config, logs and state live under **`/opt/pobsync`**
-- Backup data itself is stored under a configurable **`backup_root`** (e.g. `/srv/backups`)
-- Two snapshot types:
-  - **scheduled**  
-    Participates in retention pruning (daily / weekly / monthly / yearly)
-  - **manual**  
-    Kept outside the scheduled prune chain, defaults to hardlinking from the latest scheduled snapshot
-- Minimal dependencies (currently only `PyYAML`)
-
----
+- All backup data lives on the backup server.
+- Snapshots are rsync-based and use hardlinking (--link-dest) for space efficiency.
+- Designed for scheduled runs (cron) and manual runs.
+- Minimal external dependencies (currently only PyYAML).
 
 ## Requirements
 
-- Python **3.11+**
-- `rsync`
-- `ssh`
-- Root or sudo access on the backup server
-- SSH keys already configured between backup server and remotes
+On the backup server:
 
----
+- Python 3
+- rsync
+- ssh
+- SSH key-based access from the backup server to remotes
 
-## Installation (system-wide, no venv)
+## Canonical installation (no venv, repo used only for deployment)
 
-This assumes you are installing as root or via sudo.
+This project uses a simple and explicit deployment model:
 
-From the repository root:
+- The git clone is only used as a deployment input (and later for updates).
+- Runtime code is deployed into /opt/pobsync/lib.
+- The canonical entrypoint is /opt/pobsync/bin/pobsync.
 
-```bash
-python3 -m pip install --upgrade pip
-sudo python3 -m pip install .
+### Install
+
+```git clone https://code.hosting.hippogrief.nl/hippogrief/pobsync.git
+cd pobsync
+sudo ./scripts/deploy --prefix /opt/pobsync
+
+pobsync install --backup-root /mnt/backups/pobsync (install default configurations)
+pobsync doctor (check if the installation was done correctly)
+```
+
+### Update
+
+```
+cd /path/to/pobsync
+git pull
+
+sudo ./scripts/deploy --prefix /opt/pobsync
+sudo /opt/pobsync/bin/pobsync doctor
+```
+
+## Configuration
+
+Global configuration is stored at:
+
+- /opt/pobsync/config/global.yaml
+
+Per-host configuration files are stored at:
+
+- /opt/pobsync/config/hosts/<host>.yaml
+
+## Some useful commands to get you started
+
+Create a new host configuration:
+
+`pobsync init-host <host>`
+
+List configured remotes:
+
+`pobsync list-remotes`
+
+Inspect the effective configuration for a host:
+
+`pobsync show-config <host>`
+
+## Running backups
+
+Run a scheduled backup for a host:
+
+`pobsync run-scheduled <host>`
+
+Optionally apply retention pruning after the run:
+
+`pobsync run-scheduled <host> --prune`
+
+## Scheduling (cron)
+
+Create a cron schedule (writes into /etc/cron.d/pobsync by default):
+
+`pobsync schedule create <host> --daily 02:15 --prune`
+
+List existing schedules:
+
+`pobsync schedule list`
+
+Remove a schedule:
+
+`pobsync schedule remove <host>`
+
+Cron output is redirected to:
+
+- /var/log/pobsync/<host>.cron.log
+
+## Development (optional)
+
+For development purposes you can still use an editable install, this is why pyproject.toml still exists:
+
+```
+python3 -m pip install -e .
+pobsync --help
+```
+
+For production use, always use the canonical entrypoint:
+
+/opt/pobsync/bin/pobsync

scripts/deploy

@@ -0,0 +1,97 @@
+#!/bin/sh
+# Deploy pobsync runtime into /opt/pobsync without pip/venv.
+# Copies python package sources into /opt/pobsync/lib and installs a stable entrypoint in /opt/pobsync/bin.
+
+set -eu
+
+PREFIX="/opt/pobsync"
+
+usage() {
+  echo "Usage: $0 [--prefix /opt/pobsync]" >&2
+  exit 2
+}
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --prefix)
+      [ $# -ge 2 ] || usage
+      PREFIX="$2"
+      shift 2
+      ;;
+    -h|--help)
+      usage
+      ;;
+    *)
+      echo "Unknown arg: $1" >&2
+      usage
+      ;;
+  esac
+done
+
+# Determine repo root from this script location
+SCRIPT_DIR="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)"
+REPO_ROOT="$(CDPATH= cd -- "${SCRIPT_DIR}/.." && pwd)"
+
+SRC_PKG="${REPO_ROOT}/src/pobsync"
+if [ ! -d "${SRC_PKG}" ]; then
+  echo "ERROR: expected python package at ${SRC_PKG}" >&2
+  exit 1
+fi
+
+BIN_DIR="${PREFIX}/bin"
+LIB_DIR="${PREFIX}/lib"
+DST_PKG="${LIB_DIR}/pobsync"
+BUILD_FILE="${DST_PKG}/_build.txt"
+
+mkdir -p "${BIN_DIR}" "${LIB_DIR}"
+
+# Copy code into /opt/pobsync/lib/pobsync
+# We use rsync if available (clean updates with --delete), otherwise fall back to cp -a.
+if command -v rsync >/dev/null 2>&1; then
+  rsync -a --delete \
+    --exclude '__pycache__/' \
+    --exclude '*.pyc' \
+    --exclude '*.pyo' \
+    --exclude '*.pyd' \
+    "${SRC_PKG}/" "${DST_PKG}/"
+else
+  # Fallback: wipe + copy
+  rm -rf "${DST_PKG}"
+  mkdir -p "${DST_PKG}"
+  cp -a "${SRC_PKG}/." "${DST_PKG}/"
+fi
+
+# Write build info (best-effort)
+GIT_SHA="unknown"
+if command -v git >/dev/null 2>&1 && [ -d "${REPO_ROOT}/.git" ]; then
+  GIT_SHA="$(cd "${REPO_ROOT}" && git rev-parse HEAD 2>/dev/null || echo unknown)"
+fi
+
+NOW_UTC="$(date -u +"%Y-%m-%dT%H:%M:%SZ" 2>/dev/null || echo unknown)"
+{
+  echo "deployed_at_utc=${NOW_UTC}"
+  echo "git_sha=${GIT_SHA}"
+  echo "repo_root=${REPO_ROOT}"
+} > "${BUILD_FILE}"
+
+# Install stable entrypoint that always runs code from /opt/pobsync/lib
+WRAPPER="${BIN_DIR}/pobsync"
+cat > "${WRAPPER}" <<EOF
+#!/bin/sh
+# managed-by=pobsync deploy
+set -eu
+
+PREFIX="${PREFIX}"
+export PYTHONPATH="\${PREFIX}/lib"
+export PYTHONUNBUFFERED=1
+
+exec /usr/bin/python3 -m pobsync "\$@"
+EOF
+
+chmod 0755 "${WRAPPER}"
+
+echo "OK"
+echo "- deployed package to ${DST_PKG}"
+echo "- wrote build info ${BUILD_FILE}"
+echo "- installed entrypoint ${WRAPPER}"
+

src/pobsync/cli.py

@@ -9,14 +9,18 @@ from .commands.doctor import run_doctor
 from .commands.init_host import run_init_host
 from .commands.install import run_install
 from .commands.list_remotes import run_list_remotes
+from .commands.retention_apply import run_retention_apply
 from .commands.retention_plan import run_retention_plan
 from .commands.run_scheduled import run_scheduled
+from .commands.schedule_create import run_schedule_create
+from .commands.schedule_list import run_schedule_list
+from .commands.schedule_remove import run_schedule_remove
 from .commands.show_config import dump_yaml, run_show_config
 from .commands.snapshots_list import run_snapshots_list
 from .commands.snapshots_show import run_snapshots_show
-from .errors import ConfigError, LockError, PobsyncError
-from .paths import PobsyncPaths
-from .util import is_tty, to_json_safe
+from .errors import LockError, PobsyncError
+from .schedule import CRON_FILE_DEFAULT
+from .util import to_json_safe
 
 
 def build_parser() -> argparse.ArgumentParser:
@@ -68,6 +72,9 @@ def build_parser() -> argparse.ArgumentParser:
     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.add_argument("--prune", action="store_true", help="Apply retention after a successful run (default: false)")
+    rp.add_argument("--prune-max-delete", type=int, default=10, help="Refuse to prune more than N snapshots (default: 10)")
+    rp.add_argument("--prune-protect-bases", action="store_true", help="When pruning, also keep base snapshots referenced in meta")
     rp.set_defaults(_handler=cmd_run_scheduled)
 
     # snapshots
@@ -78,34 +85,72 @@ def build_parser() -> argparse.ArgumentParser:
     sn_list.add_argument("host", help="Host name")
     sn_list.add_argument("--kind", default="all", help="scheduled|manual|incomplete|all (default: all)")
     sn_list.add_argument("--limit", type=int, default=20, help="Max results (default: 20)")
-    sn_list.add_argument(
-        "--include-incomplete",
-        action="store_true",
-        help="Include .incomplete when --kind=all (default: false)",
-    )
+    sn_list.add_argument("--include-incomplete", action="store_true", help="Include .incomplete when --kind=all")
     sn_list.set_defaults(_handler=cmd_snapshots_list)
 
     sn_show = sn_sub.add_parser("show", help="Show snapshot metadata")
     sn_show.add_argument("host", help="Host name")
     sn_show.add_argument("--kind", required=True, help="scheduled|manual|incomplete")
-    sn_show.add_argument("dirname", help="Snapshot directory name (e.g. 20260202-223807Z__K3VQEVH7)")
-    sn_show.add_argument(
-        "--tail",
-        type=int,
-        default=None,
-        help="Show last N lines of rsync.log",
-    )
+    sn_show.add_argument("dirname", help="Snapshot directory name")
+    sn_show.add_argument("--tail", type=int, default=None, help="Show last N lines of rsync.log")
     sn_show.set_defaults(_handler=cmd_snapshots_show)
 
     # retention
-    rt = sub.add_parser("retention", help="Retention management (dry-run)")
+    rt = sub.add_parser("retention", help="Retention management")
     rt_sub = rt.add_subparsers(dest="retention_cmd", required=True)
 
     rt_plan = rt_sub.add_parser("plan", help="Show retention prune plan (dry-run)")
     rt_plan.add_argument("host", help="Host name")
     rt_plan.add_argument("--kind", default="scheduled", help="scheduled|manual|all (default: scheduled)")
+    rt_plan.add_argument("--protect-bases", action="store_true", help="Also keep base snapshots referenced in meta (default: false)")
     rt_plan.set_defaults(_handler=cmd_retention_plan)
 
+    rt_apply = rt_sub.add_parser("apply", help="Apply retention plan (DESTRUCTIVE)")
+    rt_apply.add_argument("host", help="Host name")
+    rt_apply.add_argument("--kind", default="scheduled", help="scheduled|manual|all (default: scheduled)")
+    rt_apply.add_argument("--protect-bases", action="store_true", help="Also keep base snapshots referenced in meta (default: false)")
+    rt_apply.add_argument("--max-delete", type=int, default=10, help="Refuse to delete more than N snapshots (default: 10)")
+    rt_apply.add_argument("--yes", action="store_true", help="Confirm deletion")
+    rt_apply.set_defaults(_handler=cmd_retention_apply)
+
+    # schedule
+    sch = sub.add_parser("schedule", help="Manage cron schedules in /etc/cron.d/pobsync")
+    sch_sub = sch.add_subparsers(dest="schedule_cmd", required=True)
+
+    sch_create = sch_sub.add_parser("create", help="Create or update a schedule for a host")
+    sch_create.add_argument("host", help="Host name")
+
+    mode = sch_create.add_mutually_exclusive_group(required=True)
+    mode.add_argument("--cron", default=None, help='Raw cron expression (5 fields), e.g. "15 2 * * *"')
+    mode.add_argument("--daily", default=None, help="Daily at HH:MM")
+    mode.add_argument("--hourly", type=int, default=None, help="Hourly at minute N (0..59)")
+    mode.add_argument("--weekly", action="store_true", help="Weekly schedule (requires --dow and --time)")
+    mode.add_argument("--monthly", action="store_true", help="Monthly schedule (requires --day and --time)")
+
+    sch_create.add_argument("--dow", default=None, help="For --weekly: mon,tue,wed,thu,fri,sat,sun")
+    sch_create.add_argument("--day", type=int, default=None, help="For --monthly: day of month (1..31)")
+    sch_create.add_argument("--time", default=None, help="For --weekly/--monthly: HH:MM")
+
+    sch_create.add_argument("--user", default="root", help="Cron user field (default: root)")
+    sch_create.add_argument("--cron-file", default=CRON_FILE_DEFAULT, help="Cron file path (default: /etc/cron.d/pobsync)")
+
+    sch_create.add_argument("--prune", action="store_true", help="Run retention prune after successful backup")
+    sch_create.add_argument("--prune-max-delete", type=int, default=10, help="Prune guardrail (default: 10)")
+    sch_create.add_argument("--prune-protect-bases", action="store_true", help="Prune with base protection (default: false)")
+    sch_create.add_argument("--dry-run", action="store_true", help="Show actions, do not write")
+    sch_create.set_defaults(_handler=cmd_schedule_create)
+
+    sch_list = sch_sub.add_parser("list", help="List schedules from /etc/cron.d/pobsync")
+    sch_list.add_argument("--host", default=None, help="Filter by host")
+    sch_list.add_argument("--cron-file", default=CRON_FILE_DEFAULT, help="Cron file path (default: /etc/cron.d/pobsync)")
+    sch_list.set_defaults(_handler=cmd_schedule_list)
+
+    sch_remove = sch_sub.add_parser("remove", help="Remove schedule block for a host")
+    sch_remove.add_argument("host", help="Host name")
+    sch_remove.add_argument("--cron-file", default=CRON_FILE_DEFAULT, help="Cron file path (default: /etc/cron.d/pobsync)")
+    sch_remove.add_argument("--dry-run", action="store_true", help="Show actions, do not write")
+    sch_remove.set_defaults(_handler=cmd_schedule_remove)
+
     return p
 
 
@@ -143,24 +188,16 @@ def _print(result: dict[str, Any], as_json: bool) -> None:
         for a in result["actions"]:
             print(f"- {a}")
 
-    if "action" in result:
-        print(f"- {result['action']}")
-
     if "results" in result:
         for r in result["results"]:
-            ok = r.get("ok", False)
-            label = "OK" if ok else "FAIL"
+            label = "OK" if r.get("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']})"
-            elif "name" in r:
-                extra = f" ({r['name']})"
             elif "host" in r:
                 extra = f" ({r['host']})"
-
             line = f"- {label} {name}{extra}"
             if msg:
                 line += f" {msg}"
@@ -189,7 +226,6 @@ def _print(result: dict[str, Any], as_json: bool) -> None:
                 extra = " " + extra
             print(f"- {kind} {dirname} {status}{extra}")
 
-    # retention plan
     if "keep" in result and "delete" in result:
         keep = result.get("keep") or []
         delete = result.get("delete") or []
@@ -200,6 +236,9 @@ def _print(result: dict[str, Any], as_json: bool) -> None:
         print(f"- keep {len(keep)}")
         print(f"- delete {len(delete)}")
 
+        if result.get("protect_bases") is True:
+            print("- protect_bases true")
+
         if keep:
             print("- keep:")
             for d in keep:
@@ -219,18 +258,33 @@ def _print(result: dict[str, Any], as_json: bool) -> None:
                     extra = " " + extra
                 print(f"  - {dirname}{extra}")
 
+    if "schedules" in result:
+        for s in result["schedules"]:
+            host = s.get("host", "?")
+            cron = s.get("cron") or "unknown"
+            user = s.get("user") or "unknown"
+
+            prune = bool(s.get("prune", False))
+            prune_max = s.get("prune_max_delete", None)
+            protect = bool(s.get("prune_protect_bases", False))
+
+            extra = ""
+            if prune:
+                extra = " prune"
+                if isinstance(prune_max, int):
+                    extra += f" max_delete={prune_max}"
+                if protect:
+                    extra += " protect_bases"
+
+            print(f"- {host} {cron} {user}{extra}")
+
 
 def cmd_install(args: argparse.Namespace) -> int:
     prefix = Path(args.prefix)
     retention = parse_retention(args.retention)
-
-    backup_root = args.backup_root
-    if backup_root is None and is_tty():
-        backup_root = input("backup_root (absolute path, not '/'): ").strip() or None
-
     result = run_install(
         prefix=prefix,
-        backup_root=backup_root,
+        backup_root=args.backup_root,
         retention=retention,
         dry_run=bool(args.dry_run),
         force=bool(args.force),
@@ -241,38 +295,15 @@ def cmd_install(args: argparse.Namespace) -> int:
 
 def cmd_init_host(args: argparse.Namespace) -> int:
     prefix = Path(args.prefix)
-
-    address = args.address
-    if address is None and is_tty():
-        address = input("address (hostname or ip): ").strip() or None
-    if not address:
-        raise ConfigError("--address is required (or interactive input)")
-
-    if args.retention is None:
-        from .config.load import load_global_config
-
-        paths = PobsyncPaths(home=prefix)
-        global_cfg = load_global_config(paths.global_config_path)
-        retention = global_cfg.get("retention_defaults") or {
-            "daily": 14,
-            "weekly": 8,
-            "monthly": 12,
-            "yearly": 0,
-        }
-    else:
-        retention = parse_retention(args.retention)
-
-    excludes_replace = args.exclude_replace if args.exclude_replace is not None else None
-
     result = run_init_host(
         prefix=prefix,
         host=args.host,
-        address=address,
-        retention=retention,
+        address=args.address,
+        retention=args.retention,
         ssh_user=args.ssh_user,
         ssh_port=args.ssh_port,
         excludes_add=list(args.exclude_add),
-        excludes_replace=excludes_replace,
+        excludes_replace=args.exclude_replace,
         includes=list(args.include),
         dry_run=bool(args.dry_run),
         force=bool(args.force),
@@ -281,26 +312,9 @@ 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),
-    )
+    result = run_doctor(prefix=prefix, host=args.host, connect=bool(args.connect), rsync_dry_run=bool(args.rsync_dry_run))
     _print(result, as_json=bool(args.json))
     return 0 if result.get("ok") else 1
 
@@ -312,9 +326,26 @@ def cmd_list_remotes(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_run_scheduled(args: argparse.Namespace) -> int:
     prefix = Path(args.prefix)
-    result = run_scheduled(prefix=prefix, host=args.host, dry_run=bool(args.dry_run))
+    result = run_scheduled(
+        prefix=prefix,
+        host=args.host,
+        dry_run=bool(args.dry_run),
+        prune=bool(args.prune),
+        prune_max_delete=int(args.prune_max_delete),
+        prune_protect_bases=bool(args.prune_protect_bases),
+    )
     _print(result, as_json=bool(args.json))
     return 0 if result.get("ok") else 2
 
@@ -334,32 +365,73 @@ def cmd_snapshots_list(args: argparse.Namespace) -> int:
 
 def cmd_snapshots_show(args: argparse.Namespace) -> int:
     prefix = Path(args.prefix)
-    result = run_snapshots_show(
-        prefix=prefix,
-        host=args.host,
-        kind=args.kind,
-        dirname=args.dirname,
-        tail=args.tail,
-    )
-
+    result = run_snapshots_show(prefix=prefix, host=args.host, kind=args.kind, dirname=args.dirname, tail=args.tail)
     if args.json:
         _print(result, as_json=True)
     else:
         print(dump_yaml(result.get("meta", {})).rstrip())
         if result.get("log_path"):
             print(f"\n# rsync.log: {result['log_path']}")
-
         if result.get("log_tail"):
             print("\n# rsync.log (tail)")
             for line in result["log_tail"]:
                 print(line)
-
     return 0 if result.get("ok") else 1
 
 
 def cmd_retention_plan(args: argparse.Namespace) -> int:
     prefix = Path(args.prefix)
-    result = run_retention_plan(prefix=prefix, host=args.host, kind=args.kind)
+    result = run_retention_plan(prefix=prefix, host=args.host, kind=args.kind, protect_bases=bool(args.protect_bases))
+    _print(result, as_json=bool(args.json))
+    return 0 if result.get("ok") else 1
+
+
+def cmd_retention_apply(args: argparse.Namespace) -> int:
+    prefix = Path(args.prefix)
+    result = run_retention_apply(
+        prefix=prefix,
+        host=args.host,
+        kind=args.kind,
+        protect_bases=bool(args.protect_bases),
+        yes=bool(args.yes),
+        max_delete=int(args.max_delete),
+    )
+    _print(result, as_json=bool(args.json))
+    return 0 if result.get("ok") else 1
+
+
+def cmd_schedule_create(args: argparse.Namespace) -> int:
+    prefix = Path(args.prefix)
+    result = run_schedule_create(
+        host=args.host,
+        prefix=prefix,
+        cron_file=Path(args.cron_file),
+        cron_expr=args.cron,
+        daily=args.daily,
+        hourly=args.hourly,
+        weekly=bool(args.weekly),
+        dow=args.dow,
+        time=args.time,
+        monthly=bool(args.monthly),
+        day=args.day,
+        user=args.user,
+        prune=bool(args.prune),
+        prune_max_delete=int(args.prune_max_delete),
+        prune_protect_bases=bool(args.prune_protect_bases),
+        dry_run=bool(args.dry_run),
+    )
+    _print(result, as_json=bool(args.json))
+    return 0 if result.get("ok") else 1
+
+
+def cmd_schedule_list(args: argparse.Namespace) -> int:
+    result = run_schedule_list(cron_file=Path(args.cron_file), host=args.host)
+    _print(result, as_json=bool(args.json))
+    return 0 if result.get("ok") else 1
+
+
+def cmd_schedule_remove(args: argparse.Namespace) -> int:
+    result = run_schedule_remove(host=args.host, cron_file=Path(args.cron_file), dry_run=bool(args.dry_run))
     _print(result, as_json=bool(args.json))
     return 0 if result.get("ok") else 1
 

src/pobsync/commands/doctor.py

@@ -2,14 +2,17 @@ from __future__ import annotations
 
 import os
 import shutil
+import subprocess
 from pathlib import Path
 from typing import Any
 
 from ..config.load import load_global_config, load_host_config
-from ..errors import DoctorError
 from ..paths import PobsyncPaths
 from ..util import is_absolute_non_root
 
+CRON_FILE_DEFAULT = Path("/etc/cron.d/pobsync")
+LOG_DIR_DEFAULT = Path("/var/log/pobsync")
+
 
 def _check_binary(name: str) -> tuple[bool, str]:
     p = shutil.which(name)
@@ -32,6 +35,77 @@ def _check_writable_dir(path: Path) -> tuple[bool, str]:
     return True, f"ok: writable {path}"
 
 
+def _run(cmd: list[str]) -> subprocess.CompletedProcess[str]:
+    return subprocess.run(
+        cmd,
+        check=False,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        text=True,
+    )
+
+
+def _check_cron_service() -> tuple[bool, str]:
+    """
+    Best-effort check: verify cron service is active on systemd hosts.
+    If systemctl is missing, we don't fail doctor phase 1.
+    """
+    systemctl = shutil.which("systemctl")
+    if not systemctl:
+        return True, "ok: systemctl not found; cannot verify cron service status"
+
+    for svc in ("cron", "crond"):
+        cp = _run([systemctl, "is-active", svc])
+        if cp.returncode == 0 and cp.stdout.strip() == "active":
+            return True, f"ok: cron service active ({svc})"
+
+    return False, "cron service not active (tried: cron, crond)"
+
+
+def _check_cron_file_permissions(path: Path) -> tuple[bool, str]:
+    """
+    /etc/cron.d files must not be writable by group/other.
+    Owner should be root.
+    Mode can be 0600 or 0644 (both ok as long as not group/other-writable).
+    """
+    if not path.exists():
+        return True, f"ok: cron file not present ({path}); schedule may not be configured yet"
+
+    try:
+        st = path.stat()
+    except OSError as e:
+        return False, f"cannot stat cron file {path}: {e}"
+
+    if not path.is_file():
+        return False, f"cron file is not a regular file: {path}"
+
+    problems: list[str] = []
+
+    # root owner
+    if st.st_uid != 0:
+        problems.append("owner is not root")
+
+    # must not be group/other writable
+    if (st.st_mode & 0o022) != 0:
+        problems.append("writable by group/other")
+
+    if problems:
+        mode_octal = oct(st.st_mode & 0o777)
+        return False, f"unsafe cron file permissions/ownership for {path} (mode={mode_octal}): {', '.join(problems)}"
+
+    mode_octal = oct(st.st_mode & 0o777)
+    return True, f"ok: cron file permissions/ownership OK ({path}, mode={mode_octal})"
+
+
+def _check_pobsync_executable(prefix: Path) -> tuple[bool, str]:
+    exe = prefix / "bin" / "pobsync"
+    if not exe.exists():
+        return False, f"missing executable: {exe}"
+    if not os.access(str(exe), os.X_OK):
+        return False, f"not executable: {exe}"
+    return True, f"ok: executable {exe}"
+
+
 def run_doctor(prefix: Path, host: str | None, connect: bool, rsync_dry_run: bool) -> dict[str, Any]:
     # Phase 1 doctor does not perform network checks yet (connect/rsync_dry_run acknowledged).
     paths = PobsyncPaths(home=prefix)
@@ -63,6 +137,7 @@ def run_doctor(prefix: Path, host: str | None, connect: bool, rsync_dry_run: boo
     b1, m1 = _check_binary("rsync")
     results.append({"check": "binary", "name": "rsync", "ok": b1, "message": m1})
     ok = ok and b1
+
     b2, m2 = _check_binary("ssh")
     results.append({"check": "binary", "name": "ssh", "ok": b2, "message": m2})
     ok = ok and b2
@@ -81,6 +156,36 @@ def run_doctor(prefix: Path, host: str | None, connect: bool, rsync_dry_run: boo
     else:
         results.append({"check": "backup_root", "ok": False, "error": "global config not loaded"})
 
+    # ---- Scheduling checks (Step 1) ----
+
+    c_ok, c_msg = _check_cron_service()
+    results.append({"check": "schedule_cron_service", "ok": c_ok, "message": c_msg})
+    ok = ok and c_ok
+
+    f_ok, f_msg = _check_cron_file_permissions(CRON_FILE_DEFAULT)
+    results.append({"check": "schedule_cron_file", "path": str(CRON_FILE_DEFAULT), "ok": f_ok, "message": f_msg})
+    ok = ok and f_ok
+
+    # We treat missing log dir as a warning rather than hard-fail in phase 1:
+    # cron redirection may fail, but backups can still run.
+    if LOG_DIR_DEFAULT.exists():
+        l_ok, l_msg = _check_writable_dir(LOG_DIR_DEFAULT)
+        results.append({"check": "schedule_log_dir", "path": str(LOG_DIR_DEFAULT), "ok": l_ok, "message": l_msg})
+        ok = ok and l_ok
+    else:
+        results.append(
+            {
+                "check": "schedule_log_dir",
+                "path": str(LOG_DIR_DEFAULT),
+                "ok": True,
+                "message": f"ok: log dir does not exist ({LOG_DIR_DEFAULT}); cron redirection may fail (backlog: create in install)",
+            }
+        )
+
+    e_ok, e_msg = _check_pobsync_executable(prefix)
+    results.append({"check": "schedule_pobsync_executable", "path": str(prefix / "bin" / "pobsync"), "ok": e_ok, "message": e_msg})
+    ok = ok and e_ok
+
     # host checks
     if host is not None:
         host_path = paths.hosts_dir / f"{host}.yaml"

src/pobsync/commands/install.py

@@ -99,6 +99,25 @@ def write_yaml(path: Path, data: dict[str, Any], dry_run: bool, force: bool) ->
     return f"write {path}"
 
 
+def _ensure_system_log_dir(dry_run: bool) -> list[str]:
+    """
+    Best-effort: create /var/log/pobsync to match cron redirection.
+    Not fatal if it fails (e.g., insufficient permissions in a non-root install attempt).
+
+    Note: the canonical entrypoint (/opt/pobsync/bin/pobsync) is owned by scripts/deploy.
+    install only prepares the runtime layout and config.
+    """
+    actions: list[str] = []
+    log_dir = Path("/var/log/pobsync")
+    actions.append(f"mkdir -p {log_dir}")
+    if not dry_run:
+        try:
+            ensure_dir(log_dir)
+        except OSError as e:
+            actions.append(f"warn: cannot create {log_dir}: {e}")
+    return actions
+
+
 def run_install(
     prefix: Path,
     backup_root: str | None,
@@ -118,6 +137,10 @@ def run_install(
     global_cfg = build_default_global_config(paths.home, backup_root=backup_root, retention=retention)
     actions.append(write_yaml(paths.global_config_path, global_cfg, dry_run=dry_run, force=force))
 
+    # Install polish: ensure cron log directory exists.
+    # Code + entrypoint deployment is handled by scripts/deploy.
+    actions.extend(_ensure_system_log_dir(dry_run=dry_run))
+
     return {
         "ok": True,
         "actions": actions,

src/pobsync/commands/retention_apply.py

@@ -0,0 +1,103 @@
+from __future__ import annotations
+
+import shutil
+from pathlib import Path
+from typing import Any, Dict, List
+
+from ..errors import ConfigError
+from ..lock import acquire_host_lock
+from ..paths import PobsyncPaths
+from ..util import sanitize_host
+from .retention_plan import run_retention_plan
+
+
+def run_retention_apply(
+    prefix: Path,
+    host: str,
+    kind: str,
+    protect_bases: bool,
+    yes: bool,
+    max_delete: int,
+    acquire_lock: bool = True,
+) -> dict[str, Any]:
+    host = sanitize_host(host)
+
+    if kind not in {"scheduled", "manual", "all"}:
+        raise ConfigError("kind must be scheduled, manual, or all")
+
+    if not yes:
+        raise ConfigError("Refusing to delete snapshots without --yes")
+
+    if max_delete < 0:
+        raise ConfigError("--max-delete must be >= 0")
+
+    paths = PobsyncPaths(home=prefix)
+
+    def _do_apply() -> dict[str, Any]:
+        plan = run_retention_plan(prefix=prefix, host=host, kind=kind, protect_bases=bool(protect_bases))
+
+        delete_list = plan.get("delete") or []
+        if not isinstance(delete_list, list):
+            raise ConfigError("Invalid retention plan output: delete is not a list")
+
+        if max_delete == 0 and len(delete_list) > 0:
+            raise ConfigError("Deletion blocked by --max-delete=0")
+
+        if len(delete_list) > max_delete:
+            raise ConfigError(f"Refusing to delete {len(delete_list)} snapshots (exceeds --max-delete={max_delete})")
+
+        actions: List[str] = []
+        deleted: List[Dict[str, Any]] = []
+
+        for item in delete_list:
+            if not isinstance(item, dict):
+                continue
+
+            dirname = item.get("dirname")
+            snap_kind = item.get("kind")
+            snap_path = item.get("path")
+
+            if not isinstance(dirname, str) or not isinstance(snap_kind, str) or not isinstance(snap_path, str):
+                continue
+
+            # Hard safety: only allow scheduled/manual deletions from plan
+            if snap_kind not in {"scheduled", "manual"}:
+                raise ConfigError(f"Refusing to delete unsupported snapshot kind: {snap_kind!r}")
+
+            p = Path(snap_path)
+
+            if not p.exists():
+                actions.append(f"skip missing {snap_kind}/{dirname}")
+                continue
+
+            if not p.is_dir():
+                raise ConfigError(f"Refusing to delete non-directory path: {snap_path}")
+
+            shutil.rmtree(p)
+            actions.append(f"deleted {snap_kind} {dirname}")
+
+            deleted.append(
+                {
+                    "dirname": dirname,
+                    "kind": snap_kind,
+                    "path": snap_path,
+                }
+            )
+
+        return {
+            "ok": True,
+            "host": host,
+            "kind": kind,
+            "protect_bases": bool(protect_bases),
+            "max_delete": max_delete,
+            "deleted": deleted,
+            "actions": actions,
+        }
+
+    if acquire_lock:
+        with acquire_host_lock(paths.locks_dir, host, command="retention-apply"):
+            return _do_apply()
+
+    # Caller guarantees locking (used by run-scheduled)
+    return _do_apply()
+

src/pobsync/commands/retention_plan.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 from datetime import datetime, timezone
 from pathlib import Path
-from typing import Any, Dict, List
+from typing import Any, Dict, List, Optional, Tuple
 
 from ..config.load import load_global_config, load_host_config
 from ..config.merge import build_effective_config
@@ -29,7 +29,60 @@ def _parse_snapshot_dt(dirname: str, meta: dict) -> datetime:
         return datetime.fromtimestamp(0, tz=timezone.utc)
 
 
-def run_retention_plan(prefix: Path, host: str, kind: str) -> dict[str, Any]:
+def _apply_base_protection(
+    snapshots: List[Snapshot],
+    keep: set[str],
+    reasons: Dict[str, List[str]],
+) -> Tuple[set[str], Dict[str, List[str]]]:
+    """
+    Optional policy: if a kept snapshot has a base (kind+dirname), also keep that base snapshot.
+    This is NOT required for hardlink snapshots to remain readable, but can be useful
+    for performance (better base selection) or "chain" readability.
+
+    Adds reason: "base-of:<child_dirname>"
+    """
+    # Index snapshots by (kind, dirname)
+    idx: Dict[Tuple[str, str], Snapshot] = {(s.kind, s.dirname): s for s in snapshots}
+
+    changed = True
+    while changed:
+        changed = False
+
+        # Iterate over a stable list of current keep items
+        for child_dirname in list(keep):
+            # Find the child snapshot (may exist in multiple kinds; check both)
+            child: Optional[Snapshot] = None
+            for k in ("scheduled", "manual"):
+                child = idx.get((k, child_dirname))
+                if child is not None:
+                    break
+
+            if child is None:
+                continue
+
+            base = child.base
+            if not isinstance(base, dict):
+                continue
+
+            base_kind = base.get("kind")
+            base_dirname = base.get("dirname")
+            if not isinstance(base_kind, str) or not isinstance(base_dirname, str):
+                continue
+
+            base_snap = idx.get((base_kind, base_dirname))
+            if base_snap is None:
+                # Base might have been pruned already or never existed; ignore.
+                continue
+
+            if base_dirname not in keep:
+                keep.add(base_dirname)
+                reasons.setdefault(base_dirname, []).append(f"base-of:{child_dirname}")
+                changed = True
+
+    return keep, reasons
+
+
+def run_retention_plan(prefix: Path, host: str, kind: str, protect_bases: bool) -> dict[str, Any]:
     host = sanitize_host(host)
 
     if kind not in {"scheduled", "manual", "all"}:
@@ -81,14 +134,21 @@ def run_retention_plan(prefix: Path, host: str, kind: str) -> dict[str, Any]:
         now=datetime.now(timezone.utc),
     )
 
-    delete = [s for s in snapshots if s.dirname not in plan.keep]
+    keep = set(plan.keep)
+    reasons = dict(plan.reasons)
+
+    if protect_bases:
+        keep, reasons = _apply_base_protection(snapshots=snapshots, keep=keep, reasons=reasons)
+
+    delete = [s for s in snapshots if s.dirname not in keep]
 
     return {
         "ok": True,
         "host": host,
         "kind": kind,
+        "protect_bases": bool(protect_bases),
         "retention": retention,
-        "keep": sorted(plan.keep),
+        "keep": sorted(keep),
         "delete": [
             {
                 "dirname": s.dirname,
@@ -99,6 +159,6 @@ def run_retention_plan(prefix: Path, host: str, kind: str) -> dict[str, Any]:
             }
             for s in delete
         ],
-        "reasons": plan.reasons,
+        "reasons": reasons,
     }
 

src/pobsync/commands/run_scheduled.py

@@ -18,6 +18,7 @@ from ..snapshot import (
     snapshot_dir_name,
     utc_now,
 )
+from ..snapshot_meta import read_snapshot_meta
 from ..util import ensure_dir, realpath_startswith, sanitize_host, write_yaml_atomic
 
 
@@ -46,7 +47,7 @@ def _find_latest_snapshot(parent: Path) -> Path | None:
 def select_scheduled_base(dirs: HostBackupDirs) -> Path | None:
     """
     Base selection rule:
-      scheduled -> manual -> none
+    scheduled -> manual -> none
     """
     base = _find_latest_snapshot(dirs.scheduled)
     if base is not None:
@@ -54,7 +55,13 @@ def select_scheduled_base(dirs: HostBackupDirs) -> Path | None:
     return _find_latest_snapshot(dirs.manual)
 
 
-def _base_meta_from_path(base_dir: Path | None) -> dict[str, Any] | None:
+def _base_meta_from_path(base_dir: Path | None, link_dest: str | None) -> dict[str, Any] | None:
+    """
+    Build base metadata for meta.yaml.
+
+    Important: link_dest is the actual rsync --link-dest directory.
+    For our snapshot layout, that must be "<snapshot_dir>/data".
+    """
     if base_dir is None:
         return None
 
@@ -63,15 +70,19 @@ def _base_meta_from_path(base_dir: Path | None) -> dict[str, Any] | None:
         # Should not happen with current selection logic, but keep meta robust.
         kind = "unknown"
 
+    base_meta = read_snapshot_meta(base_dir)
+    base_id = base_meta.get("id") if isinstance(base_meta.get("id"), str) else None
+
     return {
         "kind": kind,
         "dirname": base_dir.name,
-        "id": None,
-        "path": None,
+        "id": base_id,
+        "path": link_dest,
     }
 
 
-def run_scheduled(prefix: Path, host: str, dry_run: bool) -> dict[str, Any]:
+def run_scheduled(prefix: Path, host: str, dry_run: bool, prune: bool = False, prune_max_delete: int | None = None, prune_protect_bases: bool = False, ) -> dict[str, Any]:
+
     host = sanitize_host(host)
     paths = PobsyncPaths(home=prefix)
 
@@ -92,7 +103,10 @@ def run_scheduled(prefix: Path, host: str, dry_run: bool) -> dict[str, Any]:
 
     # Base snapshot (absolute path)
     base_dir = select_scheduled_base(dirs)
-    link_dest = str(base_dir) if base_dir else None
+
+    # BUGFIX: rsync --link-dest must point at the snapshot "data" root, not the snapshot dir itself.
+    # Our destination root is "<incomplete>/data/", so the base root must be "<base>/data/".
+    link_dest = str(base_dir / "data") if base_dir else None
 
     ssh_cfg = cfg.get("ssh", {}) or {}
     rsync_cfg = cfg.get("rsync", {}) or {}
@@ -202,7 +216,7 @@ def run_scheduled(prefix: Path, host: str, dry_run: bool) -> dict[str, Any]:
             "started_at": format_iso_z(ts),
             "ended_at": None,
             "duration_seconds": None,
-            "base": _base_meta_from_path(base_dir),
+            "base": _base_meta_from_path(base_dir, link_dest),
             "rsync": {"exit_code": None, "command": cmd, "stats": {}},
             # Keep existing fields for future expansion / compatibility with current structure.
             "overrides": {"includes": [], "excludes": [], "base": None},

src/pobsync/commands/schedule_create.py

@@ -0,0 +1,162 @@
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any, Optional
+
+from ..errors import ConfigError
+from ..schedule import (
+    build_cron_expr_daily,
+    build_cron_expr_hourly,
+    build_cron_expr_monthly,
+    build_cron_expr_weekly,
+    normalize_cron_expr,
+    render_host_block,
+    upsert_host_block,
+    validate_cron_expr,
+)
+from ..util import ensure_dir, sanitize_host, write_text_atomic
+
+
+def _choose_cron_expr(
+    *,
+    cron_expr: Optional[str],
+    daily: Optional[str],
+    hourly: Optional[int],
+    weekly: bool,
+    dow: Optional[str],
+    time: Optional[str],
+    monthly: bool,
+    day: Optional[int],
+) -> str:
+    modes = [
+        ("cron", cron_expr is not None),
+        ("daily", daily is not None),
+        ("hourly", hourly is not None),
+        ("weekly", bool(weekly)),
+        ("monthly", bool(monthly)),
+    ]
+    chosen = [name for name, enabled in modes if enabled]
+    if len(chosen) == 0:
+        raise ConfigError("One of --cron/--daily/--hourly/--weekly/--monthly must be provided")
+    if len(chosen) > 1:
+        raise ConfigError("Choose exactly one of --cron/--daily/--hourly/--weekly/--monthly")
+
+    if cron_expr is not None:
+        validate_cron_expr(cron_expr)
+        return normalize_cron_expr(cron_expr)
+
+    if daily is not None:
+        return build_cron_expr_daily(daily)
+
+    if hourly is not None:
+        return build_cron_expr_hourly(hourly)
+
+    if weekly:
+        if dow is None or time is None:
+            raise ConfigError("--weekly requires --dow and --time")
+        return build_cron_expr_weekly(dow, time)
+
+    # monthly
+    if day is None or time is None:
+        raise ConfigError("--monthly requires --day and --time")
+    return build_cron_expr_monthly(day, time)
+
+
+def run_schedule_create(
+    *,
+    host: str,
+    prefix: Path,
+    cron_file: Path,
+    cron_expr: Optional[str],
+    daily: Optional[str],
+    hourly: Optional[int],
+    weekly: bool,
+    dow: Optional[str],
+    time: Optional[str],
+    monthly: bool,
+    day: Optional[int],
+    user: str,
+    prune: bool,
+    prune_max_delete: int,
+    prune_protect_bases: bool,
+    dry_run: bool,
+) -> dict[str, Any]:
+    host = sanitize_host(host)
+
+    if prune_max_delete < 0:
+        raise ConfigError("--prune-max-delete must be >= 0")
+
+    expr = _choose_cron_expr(
+        cron_expr=cron_expr,
+        daily=daily,
+        hourly=hourly,
+        weekly=weekly,
+        dow=dow,
+        time=time,
+        monthly=monthly,
+        day=day,
+    )
+
+    cmd = f"{prefix}/bin/pobsync --prefix {prefix} run-scheduled {host}"
+    if prune:
+        cmd += " --prune"
+        cmd += f" --prune-max-delete {int(prune_max_delete)}"
+        if prune_protect_bases:
+            cmd += " --prune-protect-bases"
+
+    log_dir = Path("/var/log/pobsync")
+    log_path = str(log_dir / f"{host}.cron.log")
+
+    block = render_host_block(
+        host=host,
+        cron_expr=expr,
+        user=user,
+        command=cmd,
+        log_path=log_path,
+        include_env=True,
+    )
+
+    try:
+        existing = cron_file.read_text(encoding="utf-8")
+    except FileNotFoundError:
+        existing = ""
+    except PermissionError as e:
+        raise ConfigError(f"Permission denied reading {cron_file}: {e}") from e
+    except OSError as e:
+        raise ConfigError(f"Failed reading {cron_file}: {e}") from e
+
+    had_block = f"# BEGIN POBSYNC host={host}" in existing
+    new_content = upsert_host_block(existing, host, block)
+
+    action_word = "updated" if had_block else "created"
+    actions = [
+        f"schedule {action_word} host={host}",
+        f"file {cron_file}",
+        f"cron {expr}",
+        f"user {user}",
+    ]
+
+    if prune:
+        actions.append(f"prune enabled (max_delete={int(prune_max_delete)})")
+        if prune_protect_bases:
+            actions.append("prune protect_bases enabled")
+
+    if dry_run:
+        actions.append("dry-run (no file written)")
+        return {"ok": True, "actions": actions, "host": host, "cron_file": str(cron_file)}
+
+    # Best-effort ensure log dir exists
+    try:
+        ensure_dir(log_dir)
+    except Exception:
+        actions.append(f"warn: could not create {log_dir}")
+
+    try:
+        write_text_atomic(cron_file, new_content)
+    except PermissionError as e:
+        raise ConfigError(f"Permission denied writing {cron_file}: {e}") from e
+    except OSError as e:
+        raise ConfigError(f"Failed writing {cron_file}: {e}") from e
+
+    return {"ok": True, "actions": actions, "host": host, "cron_file": str(cron_file)}
+

src/pobsync/commands/schedule_list.py

@@ -0,0 +1,87 @@
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any, Dict, List, Optional
+
+from ..errors import ConfigError
+from ..schedule import parse_cron_file
+from ..util import sanitize_host
+
+
+def _parse_prune_flags(command: Optional[str]) -> Dict[str, Any]:
+    """
+    Best-effort parse of flags from the command string that we generate.
+    """
+    if not command:
+        return {"prune": False, "prune_max_delete": None, "prune_protect_bases": False}
+
+    tokens = command.split()
+    prune = "--prune" in tokens
+    protect = "--prune-protect-bases" in tokens
+
+    max_delete = None
+    if "--prune-max-delete" in tokens:
+        try:
+            idx = tokens.index("--prune-max-delete")
+            if idx + 1 < len(tokens):
+                max_delete = int(tokens[idx + 1])
+        except (ValueError, IndexError):
+            max_delete = None
+
+    return {
+        "prune": bool(prune),
+        "prune_max_delete": max_delete,
+        "prune_protect_bases": bool(protect),
+    }
+
+
+def run_schedule_list(*, cron_file: Path, host: Optional[str]) -> dict[str, Any]:
+    if host is not None:
+        host = sanitize_host(host)
+
+    try:
+        content = cron_file.read_text(encoding="utf-8")
+    except FileNotFoundError:
+        content = ""
+    except PermissionError as e:
+        raise ConfigError(f"Permission denied reading {cron_file}: {e}") from e
+    except OSError as e:
+        raise ConfigError(f"Failed reading {cron_file}: {e}") from e
+
+    blocks = parse_cron_file(content)
+
+    schedules: List[Dict[str, Any]] = []
+    if host is not None:
+        b = blocks.get(host)
+        if b is None:
+            return {"ok": True, "cron_file": str(cron_file), "schedules": []}
+
+        flags = _parse_prune_flags(b.command)
+        schedules.append(
+            {
+                "host": b.host,
+                "cron": b.cron_expr,
+                "user": b.user,
+                "command": b.command,
+                "log_path": b.log_path,
+                **flags,
+            }
+        )
+        return {"ok": True, "cron_file": str(cron_file), "schedules": schedules}
+
+    for h in sorted(blocks.keys()):
+        b = blocks[h]
+        flags = _parse_prune_flags(b.command)
+        schedules.append(
+            {
+                "host": b.host,
+                "cron": b.cron_expr,
+                "user": b.user,
+                "command": b.command,
+                "log_path": b.log_path,
+                **flags,
+            }
+        )
+
+    return {"ok": True, "cron_file": str(cron_file), "schedules": schedules}
+

src/pobsync/commands/schedule_remove.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any
+
+from ..errors import ConfigError
+from ..schedule import remove_host_block
+from ..util import sanitize_host, write_text_atomic
+
+
+def run_schedule_remove(*, host: str, cron_file: Path, dry_run: bool) -> dict[str, Any]:
+    host = sanitize_host(host)
+
+    try:
+        existing = cron_file.read_text(encoding="utf-8")
+    except FileNotFoundError:
+        existing = ""
+    except PermissionError as e:
+        raise ConfigError(f"Permission denied reading {cron_file}: {e}") from e
+    except OSError as e:
+        raise ConfigError(f"Failed reading {cron_file}: {e}") from e
+
+    new_content = remove_host_block(existing, host)
+
+    actions = [f"schedule remove host={host}", f"file {cron_file}"]
+
+    if dry_run:
+        actions.append("dry-run (no file written)")
+        return {"ok": True, "actions": actions, "host": host, "cron_file": str(cron_file)}
+
+    try:
+        write_text_atomic(cron_file, new_content)
+    except PermissionError as e:
+        raise ConfigError(f"Permission denied writing {cron_file}: {e}") from e
+    except OSError as e:
+        raise ConfigError(f"Failed writing {cron_file}: {e}") from e
+
+    return {"ok": True, "actions": actions, "host": host, "cron_file": str(cron_file)}
+

src/pobsync/doctor_scheduling.py

@@ -0,0 +1,228 @@
+from __future__ import annotations
+
+import os
+import shutil
+import stat
+import subprocess
+from dataclasses import dataclass
+from typing import Any, Dict, List, Optional
+
+
+CRON_FILE_DEFAULT = "/etc/cron.d/pobsync"
+LOG_DIR_DEFAULT = "/var/log/pobsync"
+
+
+@dataclass(frozen=True)
+class DoctorCheck:
+    name: str
+    ok: bool
+    severity: str  # "error" | "warning" | "info"
+    message: str
+    details: Optional[Dict[str, Any]] = None
+
+
+def _run(cmd: List[str]) -> subprocess.CompletedProcess[str]:
+    return subprocess.run(
+        cmd,
+        check=False,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        text=True,
+    )
+
+
+def _check_cron_service() -> DoctorCheck:
+    systemctl = shutil.which("systemctl")
+    if not systemctl:
+        return DoctorCheck(
+            name="schedule.cron_service",
+            ok=True,
+            severity="warning",
+            message="systemctl not found; cannot verify cron service status",
+            details={"hint": "If cron isn't running, schedules won't execute."},
+        )
+
+    # Try both common service names
+    for svc in ("cron", "crond"):
+        cp = _run([systemctl, "is-active", svc])
+        if cp.returncode == 0 and cp.stdout.strip() == "active":
+            return DoctorCheck(
+                name="schedule.cron_service",
+                ok=True,
+                severity="info",
+                message=f"cron service is active ({svc})",
+            )
+
+    # Not active / unknown
+    return DoctorCheck(
+        name="schedule.cron_service",
+        ok=False,
+        severity="error",
+        message="cron service is not active (tried: cron, crond)",
+        details={"hint": "Enable/start cron (systemctl enable --now cron) or the equivalent on your distro."},
+    )
+
+
+def _check_cron_file_permissions(cron_file: str) -> DoctorCheck:
+    try:
+        st = os.stat(cron_file)
+    except FileNotFoundError:
+        return DoctorCheck(
+            name="schedule.cron_file",
+            ok=True,
+            severity="warning",
+            message=f"cron file not found: {cron_file}",
+            details={"hint": "Create one via: pobsync schedule create <host> ..."},
+        )
+    except OSError as e:
+        return DoctorCheck(
+            name="schedule.cron_file",
+            ok=False,
+            severity="error",
+            message=f"cannot stat cron file: {cron_file}",
+            details={"error": str(e)},
+        )
+
+    if not stat.S_ISREG(st.st_mode):
+        return DoctorCheck(
+            name="schedule.cron_file",
+            ok=False,
+            severity="error",
+            message=f"cron file is not a regular file: {cron_file}",
+        )
+
+    problems: List[str] = []
+    if st.st_uid != 0:
+        problems.append("owner is not root")
+
+    # For /etc/cron.d, file must NOT be group/other writable.
+    # (Mode may be 600 or 644; both are fine as long as not writable by group/other.)
+    if (st.st_mode & 0o022) != 0:
+        problems.append("cron file is writable by group/other (must not be)")
+
+    mode_octal = oct(st.st_mode & 0o777)
+
+    if problems:
+        return DoctorCheck(
+            name="schedule.cron_file",
+            ok=False,
+            severity="error",
+            message=f"cron file permissions/ownership look unsafe: {cron_file}",
+            details={"mode": mode_octal, "uid": st.st_uid, "problems": problems},
+        )
+
+    return DoctorCheck(
+        name="schedule.cron_file",
+        ok=True,
+        severity="info",
+        message=f"cron file permissions/ownership OK: {cron_file}",
+        details={"mode": mode_octal},
+    )
+
+
+def _check_log_dir(log_dir: str) -> DoctorCheck:
+    if not os.path.exists(log_dir):
+        return DoctorCheck(
+            name="schedule.log_dir",
+            ok=True,
+            severity="warning",
+            message=f"log directory does not exist: {log_dir}",
+            details={"hint": "Not fatal, but cron output redirection may fail. Backlog item: create in install."},
+        )
+
+    if not os.path.isdir(log_dir):
+        return DoctorCheck(
+            name="schedule.log_dir",
+            ok=False,
+            severity="error",
+            message=f"log path exists but is not a directory: {log_dir}",
+        )
+
+    if not os.access(log_dir, os.W_OK):
+        return DoctorCheck(
+            name="schedule.log_dir",
+            ok=False,
+            severity="error",
+            message=f"log directory is not writable: {log_dir}",
+        )
+
+    return DoctorCheck(
+        name="schedule.log_dir",
+        ok=True,
+        severity="info",
+        message=f"log directory OK: {log_dir}",
+    )
+
+
+def _check_pobsync_executable(prefix: str) -> DoctorCheck:
+    exe = os.path.join(prefix, "bin", "pobsync")
+    if not os.path.exists(exe):
+        return DoctorCheck(
+            name="schedule.pobsync_executable",
+            ok=False,
+            severity="error",
+            message=f"pobsync executable not found at {exe}",
+            details={"hint": "Your cron entry likely points here; verify /opt/pobsync installation."},
+        )
+
+    if not os.access(exe, os.X_OK):
+        return DoctorCheck(
+            name="schedule.pobsync_executable",
+            ok=False,
+            severity="error",
+            message=f"pobsync exists but is not executable: {exe}",
+        )
+
+    return DoctorCheck(
+        name="schedule.pobsync_executable",
+        ok=True,
+        severity="info",
+        message=f"pobsync executable OK: {exe}",
+    )
+
+
+def scheduling_checks(prefix: str, cron_file: str = CRON_FILE_DEFAULT) -> List[DoctorCheck]:
+    return [
+        _check_cron_service(),
+        _check_cron_file_permissions(cron_file),
+        _check_log_dir(LOG_DIR_DEFAULT),
+        _check_pobsync_executable(prefix),
+    ]
+
+
+def extend_doctor_result(result: Dict[str, Any], *, prefix: str, cron_file: str = CRON_FILE_DEFAULT) -> Dict[str, Any]:
+    """
+    Add scheduling-related checks into an existing doctor result dict.
+
+    This is designed to be additive and low-risk:
+    - If result has a "checks" list, we append items.
+    - If result has "ok", we AND it with any error-level failures.
+    """
+    checks = scheduling_checks(prefix=prefix, cron_file=cron_file)
+
+    # Normalize result structure
+    existing = result.get("checks")
+    if not isinstance(existing, list):
+        existing = []
+        result["checks"] = existing
+
+    for c in checks:
+        existing.append(
+            {
+                "name": c.name,
+                "ok": c.ok,
+                "severity": c.severity,
+                "message": c.message,
+                "details": c.details or {},
+            }
+        )
+
+    # Update overall ok: errors make it false; warnings do not.
+    overall_ok = bool(result.get("ok", True))
+    for c in checks:
+        if c.severity == "error" and not c.ok:
+            overall_ok = False
+    result["ok"] = overall_ok
+
+    return result
+

src/pobsync/schedule.py

@@ -0,0 +1,235 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Dict, List, Optional, Tuple
+
+
+CRON_FILE_DEFAULT = "/etc/cron.d/pobsync"
+BEGIN_PREFIX = "# BEGIN POBSYNC host="
+END_PREFIX = "# END POBSYNC host="
+
+
+@dataclass(frozen=True)
+class ScheduleBlock:
+    host: str
+    raw_lines: List[str]          # full block including begin/end markers
+    cron_expr: Optional[str]      # "m h dom mon dow"
+    user: Optional[str]
+    command: Optional[str]
+    log_path: Optional[str]
+
+
+def normalize_cron_expr(expr: str) -> str:
+    return " ".join(expr.strip().split())
+
+
+def validate_cron_expr(expr: str) -> None:
+    parts = normalize_cron_expr(expr).split(" ")
+    if len(parts) != 5:
+        raise ValueError("cron expression must have exactly 5 fields (m h dom mon dow)")
+
+
+def parse_hhmm(s: str) -> Tuple[int, int]:
+    s = s.strip()
+    if ":" not in s:
+        raise ValueError("time must be HH:MM")
+    a, b = s.split(":", 1)
+    if not a.isdigit() or not b.isdigit():
+        raise ValueError("time must be HH:MM")
+    h = int(a)
+    m = int(b)
+    if h < 0 or h > 23:
+        raise ValueError("hour must be 0..23")
+    if m < 0 or m > 59:
+        raise ValueError("minute must be 0..59")
+    return h, m
+
+
+def parse_dow(s: str) -> int:
+    """
+    Accept: mon,tue,wed,thu,fri,sat,sun (case-insensitive)
+    Return cron day-of-week number: 0=sun, 1=mon, ... 6=sat
+    """
+    x = s.strip().lower()
+    mapping = {
+        "sun": 0,
+        "mon": 1,
+        "tue": 2,
+        "wed": 3,
+        "thu": 4,
+        "fri": 5,
+        "sat": 6,
+    }
+    if x not in mapping:
+        raise ValueError("dow must be one of: mon,tue,wed,thu,fri,sat,sun")
+    return mapping[x]
+
+
+def build_cron_expr_daily(hhmm: str) -> str:
+    h, m = parse_hhmm(hhmm)
+    return f"{m} {h} * * *"
+
+
+def build_cron_expr_hourly(minute: int = 0) -> str:
+    if minute < 0 or minute > 59:
+        raise ValueError("minute must be 0..59")
+    return f"{minute} * * * *"
+
+
+def build_cron_expr_weekly(dow: str, hhmm: str) -> str:
+    h, m = parse_hhmm(hhmm)
+    dow_num = parse_dow(dow)
+    return f"{m} {h} * * {dow_num}"
+
+
+def build_cron_expr_monthly(day: int, hhmm: str) -> str:
+    if day < 1 or day > 31:
+        raise ValueError("day must be 1..31")
+    h, m = parse_hhmm(hhmm)
+    return f"{m} {h} {day} * *"
+
+
+def render_host_block(
+    host: str,
+    cron_expr: str,
+    user: str,
+    command: str,
+    log_path: Optional[str],
+    include_env: bool = True,
+) -> str:
+    validate_cron_expr(cron_expr)
+    cron_expr = normalize_cron_expr(cron_expr)
+
+    lines: List[str] = []
+    lines.append(f"{BEGIN_PREFIX}{host}")
+    lines.append("# managed-by=pobsync")
+    if include_env:
+        lines.append("SHELL=/bin/sh")
+        lines.append("PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin")
+
+    cron_line = f"{cron_expr} {user} {command}"
+    if log_path:
+        cron_line += f" >>{log_path} 2>&1"
+    lines.append(cron_line)
+
+    lines.append(f"{END_PREFIX}{host}")
+    return "\n".join(lines) + "\n"
+
+
+def parse_cron_file(content: str) -> Dict[str, ScheduleBlock]:
+    blocks: Dict[str, ScheduleBlock] = {}
+    lines = content.splitlines()
+
+    i = 0
+    while i < len(lines):
+        line = lines[i]
+        if line.startswith(BEGIN_PREFIX):
+            host = line[len(BEGIN_PREFIX) :].strip()
+            block_lines = [line]
+            i += 1
+            while i < len(lines):
+                block_lines.append(lines[i])
+                if lines[i].strip() == f"{END_PREFIX}{host}":
+                    break
+                i += 1
+
+            cron_expr, user, command, log_path = _extract_cron_line(block_lines)
+            blocks[host] = ScheduleBlock(
+                host=host,
+                raw_lines=block_lines,
+                cron_expr=cron_expr,
+                user=user,
+                command=command,
+                log_path=log_path,
+            )
+        i += 1
+
+    return blocks
+
+
+def _extract_cron_line(block_lines: List[str]) -> Tuple[Optional[str], Optional[str], Optional[str], Optional[str]]:
+    for raw in block_lines:
+        line = raw.strip()
+        if not line:
+            continue
+        if line.startswith("#"):
+            continue
+        # skip env-like lines
+        if "=" in line and line.split("=", 1)[0].isidentifier():
+            continue
+
+        parts = line.split()
+        if len(parts) < 7:
+            continue
+
+        cron_expr = " ".join(parts[0:5])
+        user = parts[5]
+        cmd = " ".join(parts[6:])
+
+        log_path = None
+        if ">>" in cmd:
+            before, after = cmd.split(">>", 1)
+            cmd = before.rstrip()
+            after_parts = after.strip().split()
+            if after_parts:
+                log_path = after_parts[0]
+
+        return cron_expr, user, cmd, log_path
+
+    return None, None, None, None
+
+
+def upsert_host_block(content: str, host: str, new_block: str) -> str:
+    lines = content.splitlines()
+    out: List[str] = []
+    i = 0
+    replaced = False
+
+    begin = f"{BEGIN_PREFIX}{host}"
+    end = f"{END_PREFIX}{host}"
+
+    while i < len(lines):
+        if lines[i].strip() == begin:
+            replaced = True
+            # skip until end marker (inclusive)
+            i += 1
+            while i < len(lines) and lines[i].strip() != end:
+                i += 1
+            if i < len(lines):
+                i += 1  # skip end marker
+            out.extend(new_block.rstrip("\n").splitlines())
+            continue
+
+        out.append(lines[i])
+        i += 1
+
+    if not replaced:
+        if out and out[-1].strip() != "":
+            out.append("")
+        out.extend(new_block.rstrip("\n").splitlines())
+
+    return "\n".join(out).rstrip() + "\n"
+
+
+def remove_host_block(content: str, host: str) -> str:
+    lines = content.splitlines()
+    out: List[str] = []
+    i = 0
+
+    begin = f"{BEGIN_PREFIX}{host}"
+    end = f"{END_PREFIX}{host}"
+
+    while i < len(lines):
+        if lines[i].strip() == begin:
+            i += 1
+            while i < len(lines) and lines[i].strip() != end:
+                i += 1
+            if i < len(lines):
+                i += 1  # skip end marker
+            continue
+
+        out.append(lines[i])
+        i += 1
+
+    return "\n".join(out).rstrip() + "\n"
+

src/pobsync/util.py

@@ -68,10 +68,10 @@ def write_yaml_atomic(path: Path, data: Any) -> None:
     Write YAML to `path` atomically.
 
     Strategy:
-      - Write to a temp file in the same directory
-      - fsync temp file
-      - os.replace(temp, path) (atomic on POSIX)
-      - fsync directory entry (best-effort)
+    - Write to a temp file in the same directory
+    - fsync temp file
+    - os.replace(temp, path) (atomic on POSIX)
+    - fsync directory entry (best-effort)
 
     This helps avoid partial/corrupt meta files on crashes.
     """
@@ -119,3 +119,57 @@ def write_yaml_atomic(path: Path, data: Any) -> None:
             except OSError:
                 pass
 
+
+def write_text_atomic(path: Path, content: str) -> None:
+    """
+    Write text to `path` atomically.
+
+    Strategy:
+    - Write to a temp file in the same directory
+    - fsync temp file
+    - os.replace(temp, path) (atomic on POSIX)
+    - fsync directory entry (best-effort)
+
+    This helps avoid partial/corrupt files on crashes.
+    """
+    parent = path.parent
+    parent.mkdir(parents=True, exist_ok=True)
+
+    tmp_fd: int | None = None
+    tmp_path: Path | None = None
+
+    try:
+        with tempfile.NamedTemporaryFile(
+            mode="w",
+            encoding="utf-8",
+            dir=str(parent),
+            prefix=path.name + ".",
+            suffix=".tmp",
+            delete=False,
+        ) as tf:
+            tmp_fd = tf.fileno()
+            tmp_path = Path(tf.name)
+            tf.write(content)
+            tf.flush()
+            os.fsync(tmp_fd)
+
+        os.replace(str(tmp_path), str(path))
+
+        # Best-effort directory fsync (helps durability across power loss on some FS)
+        try:
+            dir_fd = os.open(str(parent), os.O_DIRECTORY)
+            try:
+                os.fsync(dir_fd)
+            finally:
+                os.close(dir_fd)
+        except OSError:
+            pass
+
+    finally:
+        # If anything failed before replace(), try to clean up temp file
+        if tmp_path is not None and tmp_path.exists():
+            try:
+                tmp_path.unlink()
+            except OSError:
+                pass
+