From fe45272f7c458e81b31834383704ea3f6a8400a5 Mon Sep 17 00:00:00 2001
From: Slawomir Koszewski <slawek@koszewscy.waw.pl>
Date: Sun, 25 Oct 2026 20:18:00 +0100
Subject: [PATCH] feature: the router makes scheduled backups to a local
 folder, copied to the cloud with rclone, or to a Proxmox Backup Server, and
 vpn-router-backup restores them.

---
 ADR.md                                        |  48 ++
 README.md                                     | 150 ++++++-
 debian-package/debian/changelog               |  33 ++
 debian-package/debian/control                 |   9 +-
 debian-package/debian/install                 |   2 +
 debian-package/debian/postrm                  |  13 +-
 debian-package/debian/prerm                   |   9 +-
 debian-package/debian/rules                   |   1 +
 .../vpn-router.vpn-router-backup.service      |  11 +
 .../debian/vpn-router.vpn-router-backup.timer |  10 +
 debian-package/src/usr/lib/vpn-router/setup   |  26 ++
 .../src/usr/lib/vpn-router/vpnrouter.py       |  74 ++++
 .../usr/lib/vpn-router/vpnrouter_backup.py    | 412 ++++++++++++++++++
 debian-package/src/usr/lib/vpn-router/web     |  90 +++-
 debian-package/src/usr/sbin/vpn-router-backup |  98 +++++
 .../doc/vpn-router/vpn-router.json.example    |  19 +
 16 files changed, 986 insertions(+), 19 deletions(-)
 create mode 100644 debian-package/debian/vpn-router.vpn-router-backup.service
 create mode 100644 debian-package/debian/vpn-router.vpn-router-backup.timer
 create mode 100644 debian-package/src/usr/lib/vpn-router/vpnrouter_backup.py
 create mode 100755 debian-package/src/usr/sbin/vpn-router-backup

diff --git a/ADR.md b/ADR.md
index 24a0cbb..dc0d0a0 100644
--- a/ADR.md
+++ b/ADR.md
@@ -679,3 +679,51 @@ one connection, dropping the others. A change through the API is answered before
 applied it, so a configuration that setup cannot apply shows in the setup state, not in the
 answer. A connection with a key file keeps it until a key is given through the API, which then
 replaces the file.
+
+## ADR-26: Backups are a staged, consistent copy, archived locally with tar and zstd or sent to a Proxmox Backup Server
+
+Status: Accepted
+
+Context: An image backup of the VM, such as Azure Backup, restores the whole disk. It cannot be
+exported as a file, read on another system, or restored onto a new VM. The state that matters is
+small, but it is spread over several places: `vpn-router.json` and the secrets, the PKI, the
+WireGuard keys and peers, the firewall rules, the slapd directory and, optionally, the
+PostgreSQL database. Only part of it can be made again: the CA, the password hashes and the TOTP
+secrets cannot. The API and the command-line tools change the configuration, the PKI and the
+directory while the router runs.
+
+Decision: `vpn-router-backup run`, started by a timer on `backup.schedule`, stages a copy of that
+state in one directory and then archives or sends it.
+
+- **Consistency:** the files are copied and the directory is written with `slapcat` while the
+  configuration lock and the users lock are held, the locks every change of the API and the tools
+  takes, so a user, their certificate and the CRL are copied together. `slapcat` reads the MDB
+  database consistently while slapd runs (ADR-4), and `pg_dump` reads a snapshot. Files that
+  `vpn-router-setup` regenerates are left out.
+- **Local target:** a tar archive compressed with zstd, both from the Ubuntu archive, so a local
+  backup needs nothing else and the archive can be read on any Linux system. A `pxar` archive
+  would need Proxmox's client and is not compressed.
+- **Retention:** local archives are pruned by the rules of Proxmox Backup Server's prune, so the
+  settings mean the same for both targets and can be checked with Proxmox's prune simulator.
+  Settings finer than the schedule do not apply.
+- **Cloud copy:** rclone, from the Ubuntu archive, copies the archives to any storage it
+  supports. The remote is defined in `/etc/vpn-router/rclone.conf` with `rclone config`, since
+  each backend has its own settings. `vpn-router.json` names only the remote, and the
+  configuration file is part of the backup. `sync` makes retention apply to the remote as well;
+  `copy` leaves it to the storage's lifecycle rules. Only this host's archives are included, so a
+  shared remote path is safe.
+- **Proxmox Backup Server:** the static `proxmox-backup-client` sends the staged directory as one
+  `pxar` archive of a host snapshot. Deduplication makes frequent backups cheap. The server's
+  prune jobs keep the snapshots, so the token needs only `DatastoreBackup`, which cannot delete.
+  The client is a suggestion, not a dependency, because it comes from Proxmox's repository, which
+  an Ubuntu system does not know. Without it, only a PBS backup fails.
+- **Restore:** only on the command line, as root. It replaces the directory and the database, so
+  it stops their services, keeps what it replaces and lets `vpn-router-setup` rebuild the rest.
+  The API offers no restore, so a stolen admin session cannot replace the router's keys.
+
+Consequences: A backup holds every secret of the router, including the CA key, in plain form
+unless a PBS key file encrypts it, so where it is kept must be as safe as the router. A restore
+onto another VM brings back the old interface names and addresses, which may need changing. The
+timer's schedules are systemd's shorthands, so all backups of one schedule start at the same
+moment. A change of the users between the end of the copy and the next backup is in no backup
+until then.
diff --git a/README.md b/README.md
index d3b5133..440e85c 100644
--- a/README.md
+++ b/README.md
@@ -143,6 +143,23 @@ must have the type shown below; an unknown section or setting is an error.
 | `metrics` | `keep_daily` | string | `3 months` | How long the daily summaries are kept |
 | `metrics` | `keep_monthly` | string | `1 year` | How long the monthly summaries are kept |
 | `metrics` | `keep_yearly` | string | `10 years` | How long the yearly summaries are kept |
+| `backup` | `enabled` | boolean | `false` | Scheduled backups (see Backups) |
+| `backup` | `schedule` | string | `daily` | `hourly`, `daily` or `weekly` |
+| `backup` | `target` | string | `local` | `local`, an archive in `backup.path`, or `pbs`, a Proxmox Backup Server |
+| `backup` | `path` | string | `/var/backups/vpn-router` | The folder of local archives, an absolute path |
+| `backup` | `keep_hourly` | integer | `24` | Hourly local archives kept, with the hourly schedule |
+| `backup` | `keep_daily` | integer | `7` | Daily local archives kept, with the hourly and the daily schedule |
+| `backup` | `keep_weekly` | integer | `4` | Weekly local archives kept |
+| `backup` | `keep_monthly` | integer | `12` | Monthly local archives kept |
+| `backup` | `keep_yearly` | integer | `0` | Yearly local archives kept |
+| `backup` | `metrics` | boolean | `false` | The backup holds the database of the metrics and the refresh tokens |
+| `backup` | `rclone_remote` | string | | `remote:path` of `/etc/vpn-router/rclone.conf` the local archives are copied to |
+| `backup` | `rclone_mode` | string | `sync` | `sync` mirrors the archives, `copy` deletes nothing in the cloud |
+| `backup` | `pbs_repository` | string | | `user@realm!token@host[:port]:datastore` |
+| `backup` | `pbs_password` | string | | The secret of the API token |
+| `backup` | `pbs_fingerprint` | string | | The SHA-256 fingerprint of the server's certificate, when the system's CAs do not verify it |
+| `backup` | `pbs_namespace` | string | | The namespace of the datastore, such as `routers/azure` |
+| `backup` | `pbs_keyfile` | string | | An encryption key of `proxmox-backup-client key create`, an absolute path |
 
 ### Site-to-site connections
 
@@ -826,6 +843,28 @@ is `{"error": ...}` with 400 for an invalid request or configuration, with the r
 connection that does not exist, 409 for a name that exists and 500 otherwise. Keys cross the
 internal network in plain HTTP, like the token.
 
+### The /backup API
+
+`/backup` shows and changes the backup settings and starts a backup, with the same token as
+`/users`.
+
+| Request | Body | Answer |
+| --- | --- | --- |
+| `GET /backup` | | `{"settings", "state", "archives", "next", "client", "rclone"}` |
+| `PUT /backup` | any of the settings of the `backup` section; an empty or absent `pbs_password` keeps the secret | `{"settings"}` |
+| `POST /backup/run` | | 202 and `{"started": true}`; 409 while a backup runs |
+
+The answer of `GET /backup` holds:
+
+- **`settings`:** the `backup` section without `pbs_password`, with `pbs_password_set`.
+- **`state`:** the last run, `null` before the first. Its `result` is `running`, `ok`, `warning` (the backup was made but the cloud copy failed), `failed` or `interrupted` (the run ended without recording its result). It also has `started`, `finished`, `target`, `archive` or `snapshot`, `size` in bytes, `removed` (the archives retention deleted), `error` and `cloud` (`{"remote", "mode", "result", "error"}`).
+- **`archives`:** the local archives of this host, newest first, as `{"name", "time", "size"}`.
+- **`next`:** the next run as systemd shows it, `null` while backups are off.
+- **`client`:** whether `proxmox-backup-client` is installed.
+- **`rclone`:** `{"installed", "config", "remotes"}`, the remotes being the sections of `rclone.conf`.
+
+A change is made, checked and applied as for `/site-to-site`.
+
 The service starts on its own, without waiting for `vpn-router-setup`, and keeps running. Every
 30 seconds it reads `web.listen`, `web.port` and `web.enabled` from `vpn-router.json` and works
 out the addresses of the interfaces `web.listen` names as `general.mode` directs; it listens on
@@ -968,11 +1007,107 @@ When `metrics.otlp_endpoint` is set, every sample is also pushed there as an OTL
 - **Authentication:** HTTP Basic with `metrics.otlp_username` and `metrics.otlp_password` when they are set.
 - **Failures:** a failed push is logged and not repeated; the next sample is pushed a minute later.
 
+## Backups
+
+While `backup.enabled` is `true`, `vpn-router-setup` runs `vpn-router-backup.timer` on `backup.schedule`. The timer starts `vpn-router-backup.service`, which runs `vpn-router-backup run`. The schedule is written to `/etc/systemd/system/vpn-router-backup.timer.d/schedule.conf`:
+
+- `hourly` runs at the start of each hour;
+- `daily` runs at midnight;
+- `weekly` runs at midnight between Sunday and Monday.
+
+A run missed while the router was off is made at the next boot.
+
+### What a backup holds
+
+A backup holds the state that `vpn-router-setup` cannot make again:
+
+| Item | Content |
+|---|---|
+| `/etc/vpn-router` | `vpn-router.json`, the secrets, `rclone.conf`, the PKI and the certificates of the users |
+| `/etc/wireguard` | The WireGuard keys and the peers |
+| `/etc/ufw`, `/etc/default/ufw` | The firewall rules |
+| `/etc/vpn-router-manager` | The Router Manager's settings, when it is installed |
+| `files/<path>` | Each `psk_file` outside `/etc/vpn-router` |
+| `ldap/vpn-router.ldif` | The user directory, written by `slapcat`: users, groups, service accounts, password hashes and TOTP secrets |
+| `postgresql/vpn-router.dump` | With `backup.metrics`, the database of the metrics and the refresh tokens, written by `pg_dump -Fc` |
+| `manifest.json` | The host, the time, the version of the package, the schedule and the items |
+
+The files and the directory are copied while the locks of the configuration and of the users are held, so no change of the API or the command-line tools falls between them; `pg_dump` reads a snapshot of its own. The copy is staged in `/var/lib/vpn-router/backup/staging`, which is removed after each run. The backup holds every secret of the router, so keep it as safe as the router itself.
+
+### Local archives
+
+With `backup.target` `local`, a backup is a tar archive compressed with zstd, `vpn-router-<host>-<UTC time>.tar.zst`, in `backup.path` (mode 0600, the folder 0700). The folder may be a mount, such as an NFS share or an Azure Files share, which exports the archives.
+
+After each backup, the archives of this host that the retention settings no longer keep are deleted. The rules are those of Proxmox Backup Server's prune:
+
+- The settings apply in order: `keep_hourly`, `keep_daily`, `keep_weekly` (ISO weeks, Monday to Sunday), `keep_monthly`, `keep_yearly`.
+- Each keeps the newest archive of each of its last N periods that have archives, in local time.
+- A period that has an archive a former setting kept is passed over.
+- A setting finer than the schedule does not apply: `keep_hourly` only with `hourly`, `keep_daily` with `hourly` and `daily`. At least one setting that applies must be above 0.
+
+### Cloud copy with rclone
+
+With `backup.rclone_remote` set, each local backup is followed by an rclone run that copies the archives of this host to the remote. rclone comes from the `rclone` package, which the package suggests:
+
+```sh
+sudo apt-get install rclone
+sudo rclone config --config /etc/vpn-router/rclone.conf
+sudo chmod 0600 /etc/vpn-router/rclone.conf
+sudo vpn-config-edit set backup.rclone_remote azure:backups/router
+sudo systemctl restart vpn-router-setup
+```
+
+The two modes:
+
+- `sync` (the default) makes the remote mirror the archives of this host, so an archive retention deletes is deleted remotely too.
+- `copy` uploads new archives and deletes nothing, so retention in the cloud is left to its own rules, such as a lifecycle policy.
+
+Other files in the remote path are left alone in both modes. A failed cloud copy leaves the local backup in place, and the run's result is `warning`.
+
+### Proxmox Backup Server
+
+With `backup.target` `pbs`, the staged copy is sent with `proxmox-backup-client` as the archive `router.pxar` of the snapshot `host/<host>/<time>`, in `backup.pbs_namespace` when it is set. The server keeps the snapshots by its own prune jobs; the router prunes nothing.
+
+The static client comes from Proxmox's client repository, which the package suggests but does not set up. Following Proxmox's installation guide, as `/etc/apt/sources.list.d/pbs-client.sources`:
+
+```text
+Types: deb
+URIs: http://download.proxmox.com/debian/pbs-client
+Suites: trixie
+Components: main
+Signed-By: /usr/share/keyrings/proxmox-archive-keyring.gpg
+```
+
+Get the key `https://enterprise.proxmox.com/debian/proxmox-archive-keyring-trixie.gpg` into `/usr/share/keyrings/proxmox-archive-keyring.gpg`, check it against the SHA-256 the [installation guide](https://pbs.proxmox.com/docs/installation.html) gives, and install `proxmox-backup-client-static`. Until it is installed, a backup to PBS fails with a message that names the package; nothing else depends on it.
+
+On the server, make an API token for the router and give the token itself the `DatastoreBackup` role on `/datastore/<store>`, or on the namespace path. `backup.pbs_repository` names the token, such as `backup@pbs!router@pbs.example.com:store`, and `backup.pbs_password` holds its secret. Set `backup.pbs_fingerprint` when the server's certificate is self-signed. With `backup.pbs_keyfile`, the snapshot is encrypted with a key of `proxmox-backup-client key create --kdf none <file>`. Keep a copy of that key away from the router, since a restore needs it.
+
+### Running, listing and restoring
+
+```sh
+sudo vpn-router-backup run          # a backup now, whether or not backups are enabled
+sudo vpn-router-backup list         # the local archives, or the snapshots on the server
+sudo vpn-router-backup restore /var/backups/vpn-router/vpn-router-router-20261025T030000Z.tar.zst
+sudo vpn-router-backup restore --pbs host/router/2026-10-25T03:00:00Z
+```
+
+Each run is recorded in `/var/lib/vpn-router/backup.json`, which `/backup` and the Router Manager show. Only one run or restore takes place at a time.
+
+`restore` is only on the command line. It shows what the backup holds and asks for `yes`, which `--yes` gives. It then:
+
+1. stops the web service, the metrics service and slapd;
+2. puts back the files;
+3. loads the directory with `slapadd` into an empty `/var/lib/ldap/vpn-router`;
+4. sets the database role's password to the restored `database.secret`, and restores the database with `pg_restore --clean` when the backup holds it;
+5. restarts `vpn-router-setup`, which regenerates everything else, followed by WireGuard, OpenVPN, strongSwan and the Router Manager, and reloads ufw.
+
+What it replaces is kept in `/var/lib/vpn-router/backup/before-restore/<UTC time>`. To restore onto a new VM, install the package first and let `vpn-router-setup` run once. The restored configuration names the interfaces of the old VM, so change them with `vpn-config-edit` if they differ.
+
 ## Router Manager
 
 The `vpn-router-manager` package, built in the repository `linux-cloud-router-manager`, is a web
-application that shows the state of the router and manages its users and site-to-site
-connections through the status web service. It can be installed on the router or on another Linux system. While it is installed on
+application that shows the state of the router and manages its users, site-to-site
+connections and backups through the status web service. It can be installed on the router or on another Linux system. While it is installed on
 the router, `vpn-router-setup` opens its port (`port` in `/etc/vpn-router-manager/manager.json`,
 7080 by default, HTTP; HTTPS is Caddy's, on `https.manager_port`) on the internal and the external
 interface; restart `vpn-router-setup` after changing it. The manager's `listen` chooses the
@@ -981,8 +1116,8 @@ interfaces it listens on.
 ## Removal
 
 `apt-get remove` stops `vpn-router-docker`, which removes the Docker rules. It terminates the
-tunnels and takes `wg-quick@wg0`, `openvpn-server@vpn-router`, `caddy` and `vpn-router-metrics`
-down, but leaves the
+tunnels and takes `wg-quick@wg0`, `openvpn-server@vpn-router`, `caddy`, `vpn-router-metrics` and
+`vpn-router-backup.timer` down, but leaves the
 configuration in place. `strongswan` is left enabled, since it is a shared service that
 may be in use by something else.
 
@@ -992,8 +1127,11 @@ before deleting it so a later reinstall starts clean. It also removes the web se
 signing key, the password file of the metrics service account, and the database of the refresh
 tokens and the metrics, its role and their password
 file when the package created them, and Caddy's configuration `/etc/caddy/vpn-router.Caddyfile`; the certificate in
-`/var/lib/caddy` belongs to the `caddy` package. Key material and users are never deleted: `/etc/vpn-router/pki`, `/etc/vpn-router/ldap`, the user directory in slapd, the
-WireGuard key pair and everything under `/etc/swanctl` are left alone.
+`/var/lib/caddy` belongs to the `caddy` package. It removes the backup timer's schedule and the
+record of the last backup. Key material, users and backups are never deleted: `/etc/vpn-router/pki`,
+`/etc/vpn-router/ldap`, `/etc/vpn-router/rclone.conf`, the user directory in slapd, the WireGuard
+key pair, everything under `/etc/swanctl`, the archives in `backup.path` and
+`/var/lib/vpn-router/backup/before-restore` are left alone.
 
 ## Building
 
diff --git a/debian-package/debian/changelog b/debian-package/debian/changelog
index bf9d2a1..404b002 100644
--- a/debian-package/debian/changelog
+++ b/debian-package/debian/changelog
@@ -1,3 +1,36 @@
+vpn-router (0.20.0-1) unstable; urgency=medium
+
+  feature: the router makes scheduled backups to a local folder, copied to the cloud with rclone, or to a Proxmox Backup Server, and vpn-router-backup restores them.
+
+  * The backup section of vpn-router.json switches on backups and sets
+    the schedule (hourly, daily or weekly), the target (local or pbs),
+    the folder, the retention of local archives, whether the metrics
+    database is included, the rclone remote and mode, and the Proxmox
+    Backup Server repository, token secret, fingerprint, namespace and
+    key file.
+  * A backup holds /etc/vpn-router, /etc/wireguard, the ufw rules, the
+    Router Manager's settings, PSK files outside /etc/vpn-router, the
+    user directory as slapcat writes it and, optionally, the database as
+    pg_dump writes it, copied while the configuration and the users are
+    locked.
+  * Local backups are tar archives compressed with zstd. Archives the
+    retention settings no longer keep are deleted by the rules of Proxmox
+    Backup Server's prune, and rclone can sync or copy the archives to a
+    remote of /etc/vpn-router/rclone.conf.
+  * Backups to a Proxmox Backup Server are made with
+    proxmox-backup-client-static, which the package suggests; the server
+    keeps them.
+  * vpn-router-backup runs a backup, lists the backups and restores a
+    local archive or a snapshot; vpn-router-backup.timer runs it on the
+    schedule.
+  * /backup of the status web service shows and changes the backup
+    settings, shows the last run, the local archives and the next run,
+    and starts a backup.
+  * The package depends on zstd and suggests rclone and
+    proxmox-backup-client-static.
+
+ -- Slawomir Koszewski <slawek@koszewscy.waw.pl>  Wed, 28 Oct 2026 10:00:00 +0100
+
 vpn-router (0.19.1-3) unstable; urgency=medium
 
   update: ADR-24 names Ubuntu's apt-daily timer, not a cron job, as what updates the package lists.
diff --git a/debian-package/debian/control b/debian-package/debian/control
index db289cd..7c7f1ed 100644
--- a/debian-package/debian/control
+++ b/debian-package/debian/control
@@ -31,14 +31,19 @@ Depends: ${misc:Depends},
          openvpn-auth-ldap,
          iproute2,
          systemd-resolved,
-         caddy
+         caddy,
+         zstd
+Suggests: rclone,
+          proxmox-backup-client-static
 Description: Linux VPN router with IPSec, road-warrior, OpenVPN and WireGuard support
  Configures a Linux host or virtual machine as a VPN router: site-to-site
  IKEv2 IPSec (strongSwan swanctl), optional road-warrior access using EAP-TLS,
  optional OpenVPN with a certificate and a password per user, kept in a local
  LDAP directory, optional WireGuard, and the routing, NAT, MSS clamping and
  firewall rules a router needs. It keeps metrics of the router in PostgreSQL
- and serves them for an OpenTelemetry Collector. Nothing in the package is
+ and serves them for an OpenTelemetry Collector, and makes scheduled backups
+ to a local folder, copied to the cloud with rclone, or to a Proxmox Backup
+ Server. Nothing in the package is
  specific to a cloud provider.
  .
  Settings live in /etc/vpn-router/vpn-router.json, which is created on first
diff --git a/debian-package/debian/install b/debian-package/debian/install
index 7d60082..98d1714 100644
--- a/debian-package/debian/install
+++ b/debian-package/debian/install
@@ -7,11 +7,13 @@ src/usr/lib/vpn-router/vpnrouter_users.py             usr/lib/vpn-router/
 src/usr/lib/vpn-router/vpnrouter_auth.py              usr/lib/vpn-router/
 src/usr/lib/vpn-router/vpnrouter_metrics.py           usr/lib/vpn-router/
 src/usr/lib/vpn-router/vpnrouter_status.py            usr/lib/vpn-router/
+src/usr/lib/vpn-router/vpnrouter_backup.py            usr/lib/vpn-router/
 src/usr/lib/vpn-router/openvpn-same-user              usr/lib/vpn-router/
 src/usr/sbin/vpn-router-user                          usr/sbin/
 src/usr/sbin/vpn-router-group                         usr/sbin/
 src/usr/sbin/vpn-router-token                         usr/sbin/
 src/usr/sbin/vpn-config-edit                          usr/sbin/
+src/usr/sbin/vpn-router-backup                        usr/sbin/
 src/usr/lib/vpn-router/simple-ca                      usr/lib/vpn-router/
 src/usr/lib/vpn-router/configure                      usr/lib/vpn-router/
 src/usr/lib/vpn-router/docker-rules                   usr/lib/vpn-router/
diff --git a/debian-package/debian/postrm b/debian-package/debian/postrm
index 09ccebc..5e8b44d 100755
--- a/debian-package/debian/postrm
+++ b/debian-package/debian/postrm
@@ -53,8 +53,12 @@ case "$1" in
               /etc/vpn-router/vpn-router.json \
               /etc/vpn-router/web.key \
               /etc/vpn-router/metrics.secret \
-              /var/lib/vpn-router/setup.done
-        rmdir --ignore-fail-on-non-empty /var/lib/vpn-router 2>/dev/null || true
+              /etc/systemd/system/vpn-router-backup.timer.d/schedule.conf \
+              /var/lib/vpn-router/setup.done \
+              /var/lib/vpn-router/backup.json
+        rmdir --ignore-fail-on-non-empty /etc/systemd/system/vpn-router-backup.timer.d 2>/dev/null || true
+        rm -rf /var/lib/vpn-router/backup/staging /var/lib/vpn-router/backup/restore
+        rmdir --ignore-fail-on-non-empty /var/lib/vpn-router/backup /var/lib/vpn-router 2>/dev/null || true
 
         # The refresh tokens' database and role, when the package created them.
         if [ -f /etc/vpn-router/database.secret ] && command -v psql >/dev/null 2>&1; then
@@ -64,8 +68,9 @@ case "$1" in
         rm -f /etc/vpn-router/database.secret
 
         # Key material and users are not package state: /etc/vpn-router/pki,
-        # /etc/vpn-router/ldap, the user directory in slapd, the WireGuard key
-        # pair and everything under /etc/swanctl are left in place.
+        # /etc/vpn-router/ldap, /etc/vpn-router/rclone.conf, the user directory
+        # in slapd, the WireGuard key pair, everything under /etc/swanctl, the
+        # backups and what a restore replaced are left in place.
         rmdir --ignore-fail-on-non-empty /etc/vpn-router 2>/dev/null || true
         ;;
 esac
diff --git a/debian-package/debian/prerm b/debian-package/debian/prerm
index 9e0c23a..a7404e8 100755
--- a/debian-package/debian/prerm
+++ b/debian-package/debian/prerm
@@ -17,10 +17,11 @@ case "$1" in
         fi
 
         # vpn-router-setup enabled wg-quick@wg0, openvpn-server@vpn-router,
-        # caddy and vpn-router-metrics, so the package takes them down again.
-        # Use the debhelper wrappers rather than systemctl, so the script
-        # behaves on a machine without systemd.
-        for unit in wg-quick@wg0.service openvpn-server@vpn-router.service caddy.service vpn-router-metrics.service; do
+        # caddy, vpn-router-metrics and the backup timer, so the package takes
+        # them down again. Use the debhelper wrappers rather than systemctl, so
+        # the script behaves on a machine without systemd.
+        for unit in wg-quick@wg0.service openvpn-server@vpn-router.service caddy.service vpn-router-metrics.service \
+                vpn-router-backup.timer; do
             if command -v deb-systemd-invoke >/dev/null 2>&1; then
                 deb-systemd-invoke stop "$unit" >/dev/null 2>&1 || true
             fi
diff --git a/debian-package/debian/rules b/debian-package/debian/rules
index 28e83bf..2b8d25a 100755
--- a/debian-package/debian/rules
+++ b/debian-package/debian/rules
@@ -8,3 +8,4 @@ override_dh_installsystemd:
 	dh_installsystemd --name=vpn-router-web --no-start
 	dh_installsystemd --name=vpn-router-metrics --no-enable --no-start
 	dh_installsystemd --name=vpn-router-bootstrap --no-enable --no-start
+	dh_installsystemd --name=vpn-router-backup --no-enable --no-start
diff --git a/debian-package/debian/vpn-router.vpn-router-backup.service b/debian-package/debian/vpn-router.vpn-router-backup.service
new file mode 100644
index 0000000..77b8dc2
--- /dev/null
+++ b/debian-package/debian/vpn-router.vpn-router-backup.service
@@ -0,0 +1,11 @@
+[Unit]
+Description=VPN Router backup
+Documentation=file:/usr/share/doc/vpn-router/README.md
+After=network-online.target slapd.service postgresql.service
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/usr/sbin/vpn-router-backup run
+Nice=10
+IOSchedulingClass=idle
diff --git a/debian-package/debian/vpn-router.vpn-router-backup.timer b/debian-package/debian/vpn-router.vpn-router-backup.timer
new file mode 100644
index 0000000..fb4e1c3
--- /dev/null
+++ b/debian-package/debian/vpn-router.vpn-router-backup.timer
@@ -0,0 +1,10 @@
+[Unit]
+Description=VPN Router backup schedule
+Documentation=file:/usr/share/doc/vpn-router/README.md
+
+[Timer]
+OnCalendar=daily
+Persistent=true
+
+[Install]
+WantedBy=timers.target
diff --git a/debian-package/src/usr/lib/vpn-router/setup b/debian-package/src/usr/lib/vpn-router/setup
index f5e6fa3..fc102ea 100755
--- a/debian-package/src/usr/lib/vpn-router/setup
+++ b/debian-package/src/usr/lib/vpn-router/setup
@@ -63,6 +63,9 @@ MANAGER_PORT   = 7080
 #: The password of the metrics service account, which setup makes and keeps (root only).
 METRICS_SECRET = pathlib.Path('/etc/vpn-router/metrics.secret')
 
+#: The schedule of the backup timer, written from backup.schedule.
+BACKUP_SCHEDULE = pathlib.Path('/etc/systemd/system/vpn-router-backup.timer.d/schedule.conf')
+
 #: The configuration of Caddy, the HTTPS proxy, which the package's drop-in for caddy.service names;
 #: Caddy runs as the user and group CADDY_GROUP, which the caddy package creates.
 CADDYFILE   = pathlib.Path('/etc/caddy/vpn-router.Caddyfile')
@@ -566,6 +569,27 @@ def manage_metrics(ctx):
     run(['systemctl', 'restart', unit], check=False)
 
 
+def manage_backup(cfg):
+    """Run the backup timer on backup.schedule while backups are enabled, and stop it when not.
+
+    The schedule is a drop-in of the timer, BACKUP_SCHEDULE, which replaces the OnCalendar of the shipped unit.
+    """
+    unit = 'vpn-router-backup.timer'
+    if not cfg['backup']['enabled']:
+        run(['systemctl', 'disable', '--now', unit], check=False)
+        if BACKUP_SCHEDULE.exists():
+            BACKUP_SCHEDULE.unlink()
+            run(['systemctl', 'daemon-reload'], check=False)
+        return
+    text = f'[Timer]\nOnCalendar=\nOnCalendar={cfg["backup"]["schedule"]}\n'
+    if not BACKUP_SCHEDULE.exists() or BACKUP_SCHEDULE.read_text(encoding='utf-8') != text:
+        BACKUP_SCHEDULE.parent.mkdir(parents=True, exist_ok=True)
+        BACKUP_SCHEDULE.write_text(text, encoding='utf-8')
+        run(['systemctl', 'daemon-reload'], check=False)
+        run(['systemctl', 'restart', unit], check=False)
+    run(['systemctl', 'enable', '--now', unit], check=False)
+
+
 def run_platform_setup(cfg, ctx):
     """Let the platform module apply its own state, if it defines any."""
     module = vpnrouter.platform_module(cfg)
@@ -734,6 +758,8 @@ def main():
     refresh_web(cfg, ctx)
     progress('running', 'metrics service')
     manage_metrics(ctx)
+    progress('running', 'backup timer')
+    manage_backup(cfg)
     if problem:
         progress('failed', failed_step, problem)
         print(f'vpn-router: error: {problem}', file=sys.stderr)
diff --git a/debian-package/src/usr/lib/vpn-router/vpnrouter.py b/debian-package/src/usr/lib/vpn-router/vpnrouter.py
index 21809f9..58f79c6 100644
--- a/debian-package/src/usr/lib/vpn-router/vpnrouter.py
+++ b/debian-package/src/usr/lib/vpn-router/vpnrouter.py
@@ -66,6 +66,11 @@ SCHEMA = {
                    'otlp_endpoint': '', 'otlp_username': '', 'otlp_password': '',
                    'keep_details': '24 hours', 'keep_hourly': '1 month', 'keep_daily': '3 months',
                    'keep_monthly': '1 year', 'keep_yearly': '10 years'},
+    'backup':     {'enabled': False, 'schedule': 'daily', 'target': 'local', 'path': '/var/backups/vpn-router',
+                   'keep_hourly': 24, 'keep_daily': 7, 'keep_weekly': 4, 'keep_monthly': 12, 'keep_yearly': 0,
+                   'metrics': False, 'rclone_remote': '', 'rclone_mode': 'sync',
+                   'pbs_repository': '', 'pbs_password': '', 'pbs_fingerprint': '', 'pbs_namespace': '',
+                   'pbs_keyfile': ''},
 }
 
 #: site_to_site maps a connection name to its settings: option -> default, the type of the default being the required type.
@@ -83,6 +88,30 @@ METRICS_KEEP = ('keep_details', 'keep_hourly', 'keep_daily', 'keep_monthly', 'ke
 #: A retention period as PostgreSQL reads an interval: a count and a unit.
 METRICS_INTERVAL = re.compile(r'^[1-9]\d{0,4} (hour|day|month|year)s?$')
 
+#: How often backups run, as systemd OnCalendar shorthands, from the most to the least often.
+BACKUP_SCHEDULES = ('hourly', 'daily', 'weekly')
+
+#: Where backups go: an archive in backup.path, or a Proxmox Backup Server.
+BACKUP_TARGETS = ('local', 'pbs')
+
+#: How rclone follows backup.path in the cloud: sync mirrors it, copy deletes nothing remotely.
+RCLONE_MODES = ('sync', 'copy')
+
+#: The retention settings of local backups, from the hourly to the yearly ones.
+BACKUP_KEEP = ('keep_hourly', 'keep_daily', 'keep_weekly', 'keep_monthly', 'keep_yearly')
+
+#: A remote of rclone.conf and an optional path: remote:path.
+RCLONE_REMOTE = re.compile(r'^[\w.][\w. -]*:\S*$')
+
+#: A PBS repository: [[auth-id@]server[:port]:]datastore.
+PBS_REPOSITORY = re.compile(r'^(\S+:)?[A-Za-z0-9_][A-Za-z0-9._-]*$')
+
+#: The SHA-256 fingerprint of a server certificate, as PBS shows it.
+PBS_FINGERPRINT = re.compile(r'^([0-9A-Fa-f]{2}:){31}[0-9A-Fa-f]{2}$')
+
+#: A PBS namespace: up to seven names joined by /.
+PBS_NAMESPACE = re.compile(r'^[A-Za-z0-9_][A-Za-z0-9._-]*(/[A-Za-z0-9_][A-Za-z0-9._-]*){0,6}$')
+
 #: The port of Let's Encrypt's HTTP challenge, which Caddy answers while HTTPS is on.
 ACME_HTTP_PORT = 80
 
@@ -412,6 +441,46 @@ def validate(cfg):
             raise ConfigError(
                 f'metrics.{option}: {keep!r} is not a count and a unit, such as "24 hours" or "3 months"')
 
+    schedule = _get(cfg, 'backup', 'schedule')
+    if schedule not in BACKUP_SCHEDULES:
+        raise ConfigError(
+            f'backup.schedule: {schedule!r} is not one of {", ".join(BACKUP_SCHEDULES)}')
+    target = _get(cfg, 'backup', 'target')
+    if target not in BACKUP_TARGETS:
+        raise ConfigError(f'backup.target: {target!r} is not one of {", ".join(BACKUP_TARGETS)}')
+    for option in ('path', 'pbs_keyfile'):
+        value = _get(cfg, 'backup', option)
+        if value and not value.startswith('/'):
+            raise ConfigError(f'backup.{option}: {value!r} is not an absolute path')
+    if not _get(cfg, 'backup', 'path'):
+        raise ConfigError('backup.path is required')
+    for option in BACKUP_KEEP:
+        if _get(cfg, 'backup', option) < 0:
+            raise ConfigError(f'backup.{option} must not be negative')
+    if target == 'local' and not any(_get(cfg, 'backup', option) for option in backup_keeps(schedule)):
+        raise ConfigError(
+            f'backup: with the {schedule} schedule, at least one of {", ".join(backup_keeps(schedule))} '
+            'is above 0')
+    remote = _get(cfg, 'backup', 'rclone_remote')
+    if remote and not RCLONE_REMOTE.match(remote):
+        raise ConfigError(f'backup.rclone_remote: {remote!r} is not a remote and a path, such as azure:backups/router')
+    rclone_mode = _get(cfg, 'backup', 'rclone_mode')
+    if rclone_mode not in RCLONE_MODES:
+        raise ConfigError(f'backup.rclone_mode: {rclone_mode!r} is not one of {", ".join(RCLONE_MODES)}')
+    if target == 'pbs':
+        repository = _get(cfg, 'backup', 'pbs_repository')
+        if not repository or not _get(cfg, 'backup', 'pbs_password'):
+            raise ConfigError('backup.pbs_repository and backup.pbs_password are required with the pbs target')
+        if not PBS_REPOSITORY.match(repository):
+            raise ConfigError(
+                f'backup.pbs_repository: {repository!r} is not of the form user@realm!token@host:datastore')
+    fingerprint = _get(cfg, 'backup', 'pbs_fingerprint')
+    if fingerprint and not PBS_FINGERPRINT.match(fingerprint):
+        raise ConfigError(f'backup.pbs_fingerprint: {fingerprint!r} is not 32 hexadecimal pairs joined by colons')
+    namespace = _get(cfg, 'backup', 'pbs_namespace')
+    if namespace and not PBS_NAMESPACE.match(namespace):
+        raise ConfigError(f'backup.pbs_namespace: {namespace!r} is not up to seven names joined by /')
+
     docker_mode = _get(cfg, 'docker', 'mode')
     if docker_mode not in DOCKER_MODES:
         raise ConfigError(
@@ -438,6 +507,11 @@ def validate(cfg):
             'a range counting as two')
 
 
+def backup_keeps(schedule):
+    """The retention settings of local backups that apply to the schedule: none finer than it."""
+    return BACKUP_KEEP[BACKUP_SCHEDULES.index(schedule):]
+
+
 def resolve_psk(connection, name):
     """Return the pre-shared key of the site_to_site connection: psk_file wins, else psk; '' when none is configured."""
     psk_file = connection['psk_file'].strip()
diff --git a/debian-package/src/usr/lib/vpn-router/vpnrouter_backup.py b/debian-package/src/usr/lib/vpn-router/vpnrouter_backup.py
new file mode 100644
index 0000000..5784365
--- /dev/null
+++ b/debian-package/src/usr/lib/vpn-router/vpnrouter_backup.py
@@ -0,0 +1,412 @@
+"""The backups of the router, for vpn-router-backup and the web service.
+
+A backup is a consistent copy of the state that setup cannot make again, staged in STAGING: the
+trees of TREES, the files of site_to_site psk_file outside them under files/, the directory as
+slapcat writes it (ldap/vpn-router.ldif), with backup.metrics the database as pg_dump writes it
+(postgresql/vpn-router.dump), and manifest.json. The trees and the directory are copied while
+the configuration lock and the users lock are held, so the configuration, the PKI and the users
+match; pg_dump reads a snapshot of its own.
+
+backup.target local writes the staging directory as a tar archive compressed with zstd,
+ARCHIVE, to backup.path, removes the archives of this host that the retention settings of the
+schedule no longer keep, and with backup.rclone_remote syncs or copies the archives of this host
+to the remote of RCLONE_CONFIG. backup.target pbs sends the staging directory to a Proxmox Backup
+Server as the archive router.pxar of the snapshot host/<host>/<time>; the server keeps them.
+
+A run holds RUN_LOCK and records itself in STATE: result running, ok, warning (the backup is
+made, the cloud copy failed) or failed, with the times, the target, the archive or snapshot,
+its size, the error and the cloud copy. restore() puts a backup back and runs setup.
+"""
+
+import contextlib
+import datetime
+import fcntl
+import json
+import os
+import pathlib
+import re
+import shutil
+import socket
+import subprocess
+import tempfile
+import time
+
+import vpnrouter
+import vpnrouter_auth
+import vpnrouter_ldap
+import vpnrouter_users
+
+STATE = pathlib.Path('/var/lib/vpn-router/backup.json')
+WORK_DIR = pathlib.Path('/var/lib/vpn-router/backup')
+STAGING = WORK_DIR / 'staging'
+RESTORE_DIR = WORK_DIR / 'restore'
+#: What a restore replaces is kept here, in a directory named after the time of the restore.
+BEFORE_RESTORE = WORK_DIR / 'before-restore'
+RUN_LOCK = pathlib.Path('/run/vpn-router/backup.lock')
+RCLONE_CONFIG = pathlib.Path('/etc/vpn-router/rclone.conf')
+PBS_CLIENT = pathlib.Path('/usr/bin/proxmox-backup-client')
+UNIT = 'vpn-router-backup.service'
+TIMER = 'vpn-router-backup.timer'
+
+#: The state a backup copies: directories and files, each where it is on the system.
+TREES = ('/etc/vpn-router', '/etc/wireguard', '/etc/ufw', '/etc/default/ufw', '/etc/vpn-router-manager')
+
+#: The name of a local archive: the host and the UTC time of the backup.
+ARCHIVE = re.compile(r'^vpn-router-(?P<host>[A-Za-z0-9][A-Za-z0-9.-]*)-(?P<stamp>\d{8}T\d{6}Z)\.tar\.zst$')
+STAMP = '%Y%m%dT%H%M%SZ'
+
+LDIF = 'ldap/vpn-router.ldif'
+DUMP = 'postgresql/vpn-router.dump'
+PBS_ARCHIVE = 'router.pxar'
+
+#: The period of each retention setting, as strftime formats of local time; weeks are ISO weeks.
+PERIODS = {'keep_hourly': '%Y-%m-%d %H', 'keep_daily': '%Y-%m-%d', 'keep_weekly': '%G-%V', 'keep_monthly': '%Y-%m',
+           'keep_yearly': '%Y'}
+
+#: The units a restore stops while it replaces the directory and the database, and the ones it restarts after setup.
+RESTORE_STOPS = ('vpn-router-web.service', 'vpn-router-metrics.service', 'slapd.service')
+RESTORE_RESTARTS = ('wg-quick@wg0.service', 'openvpn-server@vpn-router.service', 'strongswan.service',
+                    'vpn-router-manager.service')
+
+
+class Failure(Exception):
+    """A backup or a restore that cannot be done."""
+
+
+def now():
+    """The local time in ISO 8601, to the second, with its offset."""
+    return datetime.datetime.now().astimezone().isoformat(timespec='seconds')
+
+
+def host():
+    """The name of this host, which names its archives and its PBS backup group."""
+    return socket.gethostname().split('.')[0]
+
+
+def command(args, **kwargs):
+    """Run a command; Failure with its standard error when it fails."""
+    try:
+        result = subprocess.run(args, capture_output=True, text=True, **kwargs)
+    except OSError as exc:
+        raise Failure(f'{args[0]}: {exc.strerror}')
+    if result.returncode != 0:
+        raise Failure(f'{" ".join(args[:2])} failed: {result.stderr.strip() or result.stdout.strip()}')
+    return result.stdout
+
+
+def write_state(state):
+    """Write STATE in one step."""
+    STATE.parent.mkdir(parents=True, exist_ok=True)
+    descriptor, name = tempfile.mkstemp(dir=STATE.parent, prefix='.backup.json.')
+    with os.fdopen(descriptor, 'w', encoding='utf-8') as handle:
+        handle.write(json.dumps(state, indent=2) + '\n')
+    os.chmod(name, 0o600)
+    os.replace(name, STATE)
+
+
+def running():
+    """Whether a run holds RUN_LOCK."""
+    try:
+        with open(RUN_LOCK, encoding='utf-8') as handle:
+            fcntl.flock(handle, fcntl.LOCK_EX | fcntl.LOCK_NB)
+    except FileNotFoundError:
+        return False
+    except BlockingIOError:
+        return True
+    return False
+
+
+def state():
+    """The state of the last run, {} when there was none; a run that ended without recording it is interrupted."""
+    try:
+        recorded = json.loads(STATE.read_text(encoding='utf-8'))
+    except (OSError, ValueError):
+        return {}
+    if recorded.get('result') == 'running' and not running():
+        recorded['result'] = 'interrupted'
+    return recorded
+
+
+@contextlib.contextmanager
+def run_lock():
+    """Hold RUN_LOCK; Failure when another run holds it."""
+    RUN_LOCK.parent.mkdir(parents=True, exist_ok=True)
+    with open(RUN_LOCK, 'a', encoding='utf-8') as handle:
+        try:
+            fcntl.flock(handle, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        except BlockingIOError:
+            raise Failure('another backup or restore is running')
+        yield
+
+
+def archives(path):
+    """The archives of this host in path, newest first, as [{name, time, size}]; time is the UTC time of the backup."""
+    found = []
+    try:
+        entries = list(os.scandir(path))
+    except OSError:
+        return found
+    for entry in entries:
+        match = ARCHIVE.match(entry.name)
+        if match and match['host'] == host() and entry.is_file():
+            when = datetime.datetime.strptime(match['stamp'], STAMP).replace(tzinfo=datetime.timezone.utc)
+            found.append({'name': entry.name, 'time': when.isoformat(), 'size': entry.stat().st_size})
+    return sorted(found, key=lambda item: item['time'], reverse=True)
+
+
+def kept(found, keeps):
+    """The names of the archives the retention settings keep, by the rules of Proxmox Backup Server's prune.
+
+    found is newest first. The settings apply in the order of PERIODS: each keeps the newest archive of each of its
+    last N periods that have archives and no archive a former setting kept, and the older archives of those periods
+    are removed, so no later setting keeps them.
+    """
+    marks = {}
+    for option, period in PERIODS.items():
+        count = keeps.get(option, 0)
+        if not count:
+            continue
+        periods = {moment(item).strftime(period) for item in found if marks.get(item['name']) == 'keep'}
+        included = set()
+        for item in found:
+            if item['name'] in marks:
+                continue
+            key = moment(item).strftime(period)
+            if key in periods:
+                continue
+            if key not in included:
+                if len(included) >= count:
+                    break
+                included.add(key)
+                marks[item['name']] = 'keep'
+            else:
+                marks[item['name']] = 'remove'
+    return {name for name, mark in marks.items() if mark == 'keep'}
+
+
+def moment(item):
+    """The local time of an archive of archives()."""
+    return datetime.datetime.fromisoformat(item['time']).astimezone()
+
+
+def psk_files(cfg):
+    """The psk_file of each site_to_site connection outside the trees of TREES."""
+    files = []
+    for connection in cfg['site_to_site'].values():
+        name = connection['psk_file'].strip()
+        if name and not any(name == tree or name.startswith(tree + '/') for tree in TREES) and os.path.isfile(name):
+            files.append(name)
+    return files
+
+
+def database_args(cfg):
+    """The command prefix and the database argument of pg_dump and pg_restore: postgres and vpn-router, or web.database."""
+    configured = cfg['web']['database'].strip()
+    if configured:
+        return [], [f'--dbname={configured}']
+    return ['runuser', '-u', 'postgres', '--'], [f'--dbname={vpnrouter_auth.DATABASE}']
+
+
+def stage(cfg):
+    """Copy what a backup holds to STAGING, emptied first, and return the manifest."""
+    shutil.rmtree(STAGING, ignore_errors=True)
+    STAGING.mkdir(parents=True, mode=0o700)
+    trees = [tree for tree in TREES if os.path.exists(tree)]
+    files = psk_files(cfg)
+    vpnrouter_users.LOCK_FILE.parent.mkdir(parents=True, exist_ok=True)
+    with vpnrouter.config_lock(), open(vpnrouter_users.LOCK_FILE, 'w') as users:
+        fcntl.flock(users, fcntl.LOCK_EX)
+        command(['cp', '-a', '--parents', *trees, str(STAGING)])
+        if files:
+            (STAGING / 'files').mkdir()
+            command(['cp', '-a', '--parents', *files, str(STAGING / 'files')])
+        (STAGING / LDIF).parent.mkdir()
+        command(['slapcat', '-b', vpnrouter_ldap.BASE, '-l', str(STAGING / LDIF)])
+    items = trees + [f'files{name}' for name in files] + [LDIF]
+    if cfg['backup']['metrics']:
+        (STAGING / DUMP).parent.mkdir()
+        prefix, database = database_args(cfg)
+        with open(STAGING / DUMP, 'wb') as dump:
+            result = subprocess.run([*prefix, 'pg_dump', '-Fc', *database], stdout=dump, stderr=subprocess.PIPE)
+        if result.returncode != 0:
+            raise Failure(f'pg_dump failed: {result.stderr.decode(errors="replace").strip()}')
+        items.append(DUMP)
+    version = subprocess.run(['dpkg-query', '-W', '-f=${Version}', 'vpn-router'], capture_output=True, text=True)
+    manifest = {'host': host(), 'time': now(), 'version': version.stdout.strip() or None,
+                'schedule': cfg['backup']['schedule'], 'items': items}
+    (STAGING / 'manifest.json').write_text(json.dumps(manifest, indent=2) + '\n', encoding='utf-8')
+    return manifest
+
+
+def pbs_environment(cfg):
+    """The environment of proxmox-backup-client: the repository, the token secret and the fingerprint of backup."""
+    if not PBS_CLIENT.exists():
+        raise Failure(f'{PBS_CLIENT} does not exist; install proxmox-backup-client-static')
+    backup = cfg['backup']
+    environment = dict(os.environ, PBS_REPOSITORY=backup['pbs_repository'], PBS_PASSWORD=backup['pbs_password'])
+    if backup['pbs_fingerprint']:
+        environment['PBS_FINGERPRINT'] = backup['pbs_fingerprint']
+    return environment
+
+
+def pbs_options(cfg):
+    """The namespace and key file options of proxmox-backup-client from backup."""
+    options = []
+    if cfg['backup']['pbs_namespace']:
+        options += ['--ns', cfg['backup']['pbs_namespace']]
+    if cfg['backup']['pbs_keyfile']:
+        options += ['--keyfile', cfg['backup']['pbs_keyfile']]
+    return options
+
+
+def cloud(cfg):
+    """Sync or copy the archives of this host in backup.path to backup.rclone_remote; Failure when it fails."""
+    backup = cfg['backup']
+    rclone = shutil.which('rclone')
+    if not rclone:
+        raise Failure('rclone is not installed')
+    if not RCLONE_CONFIG.is_file():
+        raise Failure(f'{RCLONE_CONFIG} does not exist; make the remote with rclone config --config {RCLONE_CONFIG}')
+    command([rclone, backup['rclone_mode'], backup['path'], backup['rclone_remote'], '--config', str(RCLONE_CONFIG),
+             '--include', f'vpn-router-{host()}-*.tar.zst'])
+
+
+def run():
+    """Make a backup to backup.target as the configuration says, recording it in STATE; the recorded state."""
+    cfg = vpnrouter.load_config()
+    backup = cfg['backup']
+    started = time.time()
+    record = {'result': 'running', 'started': now(), 'finished': None, 'target': backup['target'], 'archive': None,
+              'snapshot': None, 'size': None, 'removed': [], 'error': None, 'cloud': None}
+    with run_lock():
+        write_state(record)
+        try:
+            stage(cfg)
+            if backup['target'] == 'pbs':
+                epoch = int(started)
+                command([str(PBS_CLIENT), 'backup', f'{PBS_ARCHIVE}:{STAGING}', '--backup-type', 'host',
+                         '--backup-id', host(), '--backup-time', str(epoch), *pbs_options(cfg)],
+                        env=pbs_environment(cfg))
+                stamp = datetime.datetime.fromtimestamp(epoch, datetime.timezone.utc).strftime('%Y-%m-%dT%H:%M:%SZ')
+                record['snapshot'] = f'host/{host()}/{stamp}'
+                record['size'] = sum(path.stat().st_size for path in STAGING.rglob('*') if path.is_file())
+            else:
+                path = pathlib.Path(backup['path'])
+                path.mkdir(parents=True, mode=0o700, exist_ok=True)
+                name = f'vpn-router-{host()}-{time.strftime(STAMP, time.gmtime(started))}.tar.zst'
+                partial = path / f'{name}.partial'
+                command(['tar', '--zstd', '-cf', str(partial), '-C', str(STAGING), '.'])
+                partial.chmod(0o600)
+                partial.rename(path / name)
+                record['archive'] = name
+                record['size'] = (path / name).stat().st_size
+                found = archives(path)
+                keep = kept(found, {option: backup[option] for option in vpnrouter.backup_keeps(backup['schedule'])})
+                for item in found:
+                    if item['name'] not in keep:
+                        (path / item['name']).unlink()
+                        record['removed'].append(item['name'])
+                if backup['rclone_remote']:
+                    record['cloud'] = {'remote': backup['rclone_remote'], 'mode': backup['rclone_mode'],
+                                       'result': 'ok', 'error': None}
+                    try:
+                        cloud(cfg)
+                    except Failure as exc:
+                        record['cloud'].update(result='failed', error=str(exc))
+            record['result'] = 'warning' if record['cloud'] and record['cloud']['result'] != 'ok' else 'ok'
+        except (Failure, OSError) as exc:
+            record['result'] = 'failed'
+            record['error'] = str(exc)
+        finally:
+            shutil.rmtree(STAGING, ignore_errors=True)
+            record['finished'] = now()
+            write_state(record)
+    return record
+
+
+def snapshots(cfg):
+    """The PBS snapshots of this host, as proxmox-backup-client lists them."""
+    namespace = cfg['backup']['pbs_namespace']
+    return command([str(PBS_CLIENT), 'snapshot', 'list', f'host/{host()}', *(['--ns', namespace] if namespace else [])],
+                   env=pbs_environment(cfg))
+
+
+def extract(cfg, source, pbs):
+    """Unpack a local archive, or with pbs fetch a snapshot, to RESTORE_DIR, emptied first; the manifest."""
+    shutil.rmtree(RESTORE_DIR, ignore_errors=True)
+    RESTORE_DIR.mkdir(parents=True, mode=0o700)
+    if pbs:
+        command([str(PBS_CLIENT), 'restore', source, PBS_ARCHIVE, str(RESTORE_DIR), *pbs_options(cfg)],
+                env=pbs_environment(cfg))
+    else:
+        command(['tar', '--zstd', '-xf', source, '-C', str(RESTORE_DIR)])
+    try:
+        return json.loads((RESTORE_DIR / 'manifest.json').read_text(encoding='utf-8'))
+    except (OSError, ValueError):
+        raise Failure(f'{source} is not a backup of vpn-router-backup: it has no manifest.json')
+
+
+def put_back(relative, target, saved):
+    """Move target to saved, keeping its path, and copy the staged relative path of RESTORE_DIR in its place."""
+    target = pathlib.Path(target)
+    if target.exists() or target.is_symlink():
+        keep = saved / target.relative_to('/')
+        keep.parent.mkdir(parents=True, exist_ok=True)
+        shutil.move(target, keep)
+    target.parent.mkdir(parents=True, exist_ok=True)
+    command(['cp', '-a', str(RESTORE_DIR / relative), str(target)])
+
+
+def restore(source, pbs, confirm):
+    """Put the backup back: a local archive, or with pbs a snapshot; confirm(manifest) is asked before any change.
+
+    What is replaced is kept in BEFORE_RESTORE. The services of the directory and the database are stopped while they
+    are replaced, and setup applies the configuration afterwards. Returns the directory of what was replaced, or None
+    when confirm declined.
+    """
+    cfg = vpnrouter.load_config()
+    with run_lock():
+        try:
+            manifest = extract(cfg, source, pbs)
+            if not confirm(manifest):
+                return None
+            saved = BEFORE_RESTORE / time.strftime(STAMP, time.gmtime())
+            saved.mkdir(parents=True, mode=0o700)
+            for unit in RESTORE_STOPS:
+                subprocess.run(['systemctl', 'stop', unit], capture_output=True)
+            for item in manifest['items']:
+                if item.startswith('/'):
+                    put_back(item.lstrip('/'), item, saved)
+                elif item.startswith('files/'):
+                    put_back(item, item[len('files'):], saved)
+            if LDIF in manifest['items']:
+                directory = vpnrouter_ldap.DB_DIRECTORY
+                if directory.exists():
+                    shutil.move(directory, saved / 'ldap')
+                directory.mkdir(mode=0o700)
+                command(['slapadd', '-b', vpnrouter_ldap.BASE, '-l', str(RESTORE_DIR / LDIF)])
+                command(['chown', '-R', 'openldap:openldap', str(directory)])
+            subprocess.run(['systemctl', 'start', 'slapd.service'], capture_output=True)
+            restored = vpnrouter.load_config()
+            if not restored['web']['database'].strip():
+                secret = vpnrouter_auth.DATABASE_SECRET
+                if secret.is_file() and vpnrouter_auth.psql("SELECT 1 FROM pg_roles WHERE rolname = :'v1'",
+                                                            vpnrouter_auth.DATABASE):
+                    password = secret.read_text(encoding='utf-8').strip()
+                    vpnrouter_auth.psql(f"ALTER ROLE :\"v1\" PASSWORD '{password}'", vpnrouter_auth.DATABASE)
+                vpnrouter_auth.provision(restored)
+            if DUMP in manifest['items']:
+                prefix, database = database_args(restored)
+                with open(RESTORE_DIR / DUMP, 'rb') as dump:
+                    result = subprocess.run([*prefix, 'pg_restore', '--clean', '--if-exists', *database], stdin=dump,
+                                            stdout=subprocess.DEVNULL, stderr=subprocess.PIPE)
+                if result.returncode != 0:
+                    raise Failure(f'pg_restore failed: {result.stderr.decode(errors="replace").strip()}')
+            subprocess.run(['systemctl', 'start', 'vpn-router-web.service'], capture_output=True)
+            command(['systemctl', 'restart', 'vpn-router-setup.service'])
+            for unit in RESTORE_RESTARTS:
+                subprocess.run(['systemctl', 'try-restart', unit], capture_output=True)
+            subprocess.run(['ufw', 'reload'], capture_output=True)
+            return saved
+        finally:
+            shutil.rmtree(RESTORE_DIR, ignore_errors=True)
diff --git a/debian-package/src/usr/lib/vpn-router/web b/debian-package/src/usr/lib/vpn-router/web
index 8b6fc9f..2061bf8 100644
--- a/debian-package/src/usr/lib/vpn-router/web
+++ b/debian-package/src/usr/lib/vpn-router/web
@@ -24,7 +24,9 @@ Pages:
   /site-to-site
            the site-to-site connections of the configuration: list, add, change and remove,
            applied by vpn-router-setup (see site_to_site())
-  /auth    sign-in with a user's password and TOTP code, refresh and sign-out (see auth())
+  /backup  the backup settings, the last run and the local archives: show, change and run
+           now (see backup())
+  /auth   sign-in with a user's password and TOTP code, refresh and sign-out (see auth())
   /metrics/history
            the metrics the metrics service keeps, for a view: hour, day, month or year (see
            metrics_history())
@@ -32,7 +34,7 @@ Pages:
            the databases of each PostgreSQL cluster on the router with their sizes, as JSON (see
            postgresql_databases()); /config has the clusters' settings
 
-/config, /metrics/history, /postgresql, /users, /service-accounts, /groups, /site-to-site and /account need an HS256 JWT in an Authorization: Bearer header signed
+/config, /metrics/history, /postgresql, /users, /service-accounts, /groups, /site-to-site, /backup and /account need an HS256 JWT in an Authorization: Bearer header signed
 with vpnrouter_auth.WEB_KEY (see vpnrouter_auth.verify). A token of /auth names a user in sub;
 /account serves that user, and the other paths need a member of vpnrouter_users.ADMIN_GROUP. A
 token of vpn-router-token has the admin claim and names no user; it may call every path but
@@ -67,8 +69,10 @@ the router has no features, and /config shows no configuration or interfaces.
 """
 
 import collections
+import configparser
 import json
 import os
+import shutil
 import signal
 import sys
 import threading
@@ -83,6 +87,7 @@ import ldap
 
 import vpnrouter
 import vpnrouter_auth
+import vpnrouter_backup
 import vpnrouter_metrics
 import vpnrouter_net
 import vpnrouter_serve
@@ -676,6 +681,82 @@ def site_to_site(method, path, body):
     return (201 if method == 'POST' else 200), connection_of(name, cfg['site_to_site'][name], None)
 
 
+def backup_settings(settings):
+    """The backup section as /backup shows it: its settings but pbs_password, with pbs_password_set."""
+    return {**{option: value for option, value in settings.items() if option != 'pbs_password'},
+            'pbs_password_set': bool(settings['pbs_password'])}
+
+
+def rclone_remotes():
+    """The names of the remotes of vpnrouter_backup.RCLONE_CONFIG; [] when it cannot be read, as when it is encrypted."""
+    parser = configparser.ConfigParser(interpolation=None)
+    try:
+        parser.read(vpnrouter_backup.RCLONE_CONFIG, encoding='utf-8')
+    except (OSError, configparser.Error):
+        return []
+    return parser.sections()
+
+
+def backup(method, path, body):
+    """Answer a /backup request: the HTTP status and the JSON document.
+
+      GET  /backup      {"settings", "state", "archives", "next", "client", "rclone"}: the backup section without
+                        pbs_password, with pbs_password_set; the last run (vpnrouter_backup.state), null before the
+                        first; the local archives of this host, newest first, [{name, time, size}], [] with the pbs
+                        target; the next run of the timer as systemd shows it, null while backups are disabled;
+                        whether proxmox-backup-client is installed; and {"installed", "config", "remotes"} of rclone
+      PUT  /backup      change any of the settings of the backup section; an empty or absent pbs_password keeps the
+                        current secret
+      POST /backup/run  start a backup now, without waiting for it; 409 while one runs
+
+    A change is made as /site-to-site makes one, and applied by restarting vpn-router-setup without waiting for it.
+    """
+    if body == 'invalid' or (body is not None and not isinstance(body, dict)):
+        return 400, {'error': 'the body must be a JSON object'}
+    body = body or {}
+    if (method, path) == ('POST', '/backup/run'):
+        if vpnrouter_backup.running():
+            return 409, {'error': 'a backup is running'}
+        result = run('systemctl', 'start', '--no-block', vpnrouter_backup.UNIT)
+        if result is None or result.returncode != 0:
+            return 500, {'error': f'the backup cannot be started: {result.stderr.strip() if result else "no systemctl"}'}
+        return 202, {'started': True}
+    if (method, path) not in (('GET', '/backup'), ('PUT', '/backup')):
+        return 404, {'error': f'no route {method} {path}'}
+    try:
+        if method == 'GET':
+            settings = vpnrouter.load_config()['backup']
+            timer = run('systemctl', 'show', '-p', 'NextElapseUSecRealtime', '--value', vpnrouter_backup.TIMER)
+            next_run = timer.stdout.strip() if timer and timer.returncode == 0 else ''
+            return 200, {
+                'settings': backup_settings(settings),
+                'state': vpnrouter_backup.state() or None,
+                'archives': vpnrouter_backup.archives(settings['path']) if settings['target'] == 'local' else [],
+                'next': next_run if settings['enabled'] and next_run not in ('', 'n/a') else None,
+                'client': vpnrouter_backup.PBS_CLIENT.exists(),
+                'rclone': {'installed': shutil.which('rclone') is not None,
+                           'config': vpnrouter_backup.RCLONE_CONFIG.is_file(), 'remotes': rclone_remotes()},
+            }
+        settings = {option: body[option] for option in vpnrouter.SCHEMA['backup'] if option in body}
+        if not settings.get('pbs_password'):
+            settings.pop('pbs_password', None)
+        with vpnrouter.config_lock():
+            data = vpnrouter.read_settings()
+            current = data.get('backup')
+            data['backup'] = {**(current if isinstance(current, dict) else {}), **settings}
+            cfg = vpnrouter.with_defaults(data)
+            vpnrouter.validate(cfg)
+            vpnrouter.save_config(data)
+    except vpnrouter.ConfigError as exc:
+        return 400, {'error': str(exc)}
+    except OSError as exc:
+        return 500, {'error': f'the configuration cannot be written: {exc}'}
+    except SystemExit as exc:
+        return 500, {'error': str(exc.code)}
+    run('systemctl', 'restart', '--no-block', 'vpn-router-setup.service')
+    return 200, {'settings': backup_settings(cfg['backup'])}
+
+
 def account(name, method, path, body):
     """Answer an /account request of the user named by the token with vpnrouter_users: the HTTP status and the JSON document.
 
@@ -864,7 +945,7 @@ class Handler(BaseHTTPRequestHandler):
         # A body that is not read must not be taken for the next request.
         if self.command not in ('GET', 'HEAD'):
             self.close_connection = True
-        directory = next((name for name in ('users', 'service-accounts', 'groups', 'account', 'site-to-site')
+        directory = next((name for name in ('users', 'service-accounts', 'groups', 'account', 'site-to-site', 'backup')
                           if path == f'/{name}' or path.startswith(f'/{name}/')), None)
         protected = path in ('/config', '/metrics/history', '/postgresql') or directory is not None
         signing = path in ('/auth', '/auth/refresh', '/auth/logout')
@@ -905,6 +986,9 @@ class Handler(BaseHTTPRequestHandler):
         elif directory == 'site-to-site':
             code, document = site_to_site(self.command, path, payload)
             body, kind = json.dumps(document, indent=2).encode() + b'\n', 'application/json'
+        elif directory == 'backup':
+            code, document = backup(self.command, path, payload)
+            body, kind = json.dumps(document, indent=2).encode() + b'\n', 'application/json'
         elif directory == 'service-accounts':
             code, document = service_accounts(self.command, path, payload)
             body, kind = json.dumps(document, indent=2).encode() + b'\n', 'application/json'
diff --git a/debian-package/src/usr/sbin/vpn-router-backup b/debian-package/src/usr/sbin/vpn-router-backup
new file mode 100755
index 0000000..156f5b7
--- /dev/null
+++ b/debian-package/src/usr/sbin/vpn-router-backup
@@ -0,0 +1,98 @@
+#!/usr/bin/python3
+"""Make, list and restore backups of the router (vpnrouter_backup).
+
+run makes a backup as backup in /etc/vpn-router/vpn-router.json says, whether or not backups are
+enabled, and prints its result; vpn-router-backup.service runs it on the schedule of its timer.
+list prints the local archives of this host in backup.path, newest first, or with the pbs target
+the snapshots of this host on the Proxmox Backup Server. restore puts back a local archive, or
+with --pbs a snapshot, such as host/router/2026-10-25T03:00:00Z, after showing what it holds and
+asking for yes, which --yes gives; what it replaces is kept in
+/var/lib/vpn-router/backup/before-restore. A failure is a message on standard error; the exit
+status is 2 for an invalid request and 1 for any other failure. -h or --help shows the options.
+
+  vpn-router-backup run
+  vpn-router-backup list
+  vpn-router-backup restore [--yes] ARCHIVE
+  vpn-router-backup restore [--yes] --pbs SNAPSHOT
+"""
+
+import argparse
+import os
+import sys
+
+sys.path.insert(0, '/usr/lib/vpn-router')
+
+import vpnrouter
+import vpnrouter_backup
+
+
+class Parser(argparse.ArgumentParser):
+    """An argument parser whose errors end with status 2."""
+
+    def error(self, message):
+        print(f'{self.prog}: {message}; see {self.prog} --help', file=sys.stderr)
+        sys.exit(2)
+
+
+def confirmed(manifest, yes):
+    """Whether to restore the backup of the manifest: yes, or the answer yes to the question."""
+    print(f'Backup of {manifest.get("host")} made {manifest.get("time")} by vpn-router {manifest.get("version")}:')
+    for item in manifest.get('items', []):
+        print(f'  {item}')
+    if yes:
+        return True
+    return input('Replace the router state with it? Type yes: ').strip() == 'yes'
+
+
+def main(argv):
+    parser = Parser(prog='vpn-router-backup', description='Make, list and restore backups of the router.')
+    commands = parser.add_subparsers(dest='command', required=True, parser_class=Parser)
+    commands.add_parser('run', help='make a backup now')
+    commands.add_parser('list', help='list the backups of this host')
+    restorer = commands.add_parser('restore', help='put a backup back')
+    restorer.add_argument('source', metavar='ARCHIVE|SNAPSHOT', help='a local archive, or with --pbs a snapshot')
+    restorer.add_argument('--pbs', action='store_true', help='restore a snapshot of the Proxmox Backup Server')
+    restorer.add_argument('--yes', action='store_true', help='do not ask before replacing the router state')
+    options = parser.parse_args(argv)
+    os.umask(0o077)
+
+    try:
+        if options.command == 'run':
+            record = vpnrouter_backup.run()
+            if record['result'] == 'failed':
+                print(f'vpn-router-backup: {record["error"]}', file=sys.stderr)
+                return 1
+            print(f'Backup {record["archive"] or record["snapshot"]} made, {record["size"]} bytes.')
+            for name in record['removed']:
+                print(f'Removed {name}.')
+            if record['cloud']:
+                print(f'Cloud copy to {record["cloud"]["remote"]}: {record["cloud"]["error"] or "ok"}.')
+            return 0
+        cfg = vpnrouter.load_config()
+        if options.command == 'list':
+            if cfg['backup']['target'] == 'pbs':
+                print(vpnrouter_backup.snapshots(cfg), end='')
+            else:
+                for item in vpnrouter_backup.archives(cfg['backup']['path']):
+                    print(f'{item["name"]}  {item["size"]}')
+            return 0
+        if options.pbs and options.source.startswith('/'):
+            print('vpn-router-backup: a snapshot is type/id/time, such as host/router/2026-10-25T03:00:00Z',
+                  file=sys.stderr)
+            return 2
+        saved = vpnrouter_backup.restore(options.source, options.pbs, lambda manifest: confirmed(manifest, options.yes))
+    except vpnrouter_backup.Failure as exc:
+        print(f'vpn-router-backup: {exc}', file=sys.stderr)
+        return 1
+    except OSError as exc:
+        print(f'vpn-router-backup: {exc}', file=sys.stderr)
+        return 1
+    if saved is None:
+        print('Nothing restored.')
+        return 1
+    print(f'Restored; what it replaced is in {saved}.')
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv[1:]))
diff --git a/debian-package/src/usr/share/doc/vpn-router/vpn-router.json.example b/debian-package/src/usr/share/doc/vpn-router/vpn-router.json.example
index 173f35d..33772cd 100644
--- a/debian-package/src/usr/share/doc/vpn-router/vpn-router.json.example
+++ b/debian-package/src/usr/share/doc/vpn-router/vpn-router.json.example
@@ -74,5 +74,24 @@
     "keep_daily": "3 months",
     "keep_monthly": "1 year",
     "keep_yearly": "10 years"
+  },
+  "backup": {
+    "enabled": false,
+    "schedule": "daily",
+    "target": "local",
+    "path": "/var/backups/vpn-router",
+    "keep_hourly": 24,
+    "keep_daily": 7,
+    "keep_weekly": 4,
+    "keep_monthly": 12,
+    "keep_yearly": 0,
+    "metrics": false,
+    "rclone_remote": "",
+    "rclone_mode": "sync",
+    "pbs_repository": "",
+    "pbs_password": "",
+    "pbs_fingerprint": "",
+    "pbs_namespace": "",
+    "pbs_keyfile": ""
   }
 }