Add failure logging/email notification in backup.sh; harden /opt/backup perms

.gitignore

@@ -1,3 +1,6 @@
 # Secrets — never commit
 backup.env
 encryption-key.pem
+
+# Runtime artifacts
+backup.log

README.backup.md

@@ -11,13 +11,14 @@ Everything lives in `/opt/backup/`. The connection details and credentials
 
 | File | Purpose |
 |------|---------|
-| `backup.env` | Shared config: server, datastore, namespace, token, key (sourced by both scripts) |
+| `backup.env` | Shared config: server, datastore, namespace, token, key, `NOTIFY_EMAIL` (sourced by both scripts) |
 | `backup.env.sample` | Template — copy to `backup.env` and fill in real values |
 | `setup.sh` | Install the client and create the encryption key (run once as root) |
 | `backup.sh` | Full backup of `/` with client-side encryption |
 | `restore.sh` | FUSE-mount the encrypted backup to browse/restore files |
 | `/opt/backup/encryption-key.pem` | Client-side encryption key (store a copy off-host!) |
 | `/opt/backup/exclude` | Paths excluded from the backup |
+| `backup.log` | Runtime log written by `backup.sh` (created on each run) |
 
 ## Setup
 
@@ -53,6 +54,31 @@ chmod 600 backup.env
 4. The client encrypts everything locally before uploading. The PBS only ever
    stores ciphertext and cannot read the data.
 
+The client's output is piped through `tee` into `backup.log` (the file in the
+table above). The script captures the client's exit status (via
+`set -o pipefail`), so a failed `proxmox-backup-client` run is detected even
+though its output went through `tee`.
+
+## Failure notification
+
+If `backup.sh` fails it exits non-zero and, when a mailbox is configured, emails
+the failure. Set it in `backup.env`:
+
+```
+NOTIFY_EMAIL="admin@example.com"
+```
+
+Empty (the default) disables mail. There is no `mail`/`mailx` on the hosts, so
+the script sends via Postfix directly with:
+
+```
+... | sendmail -t
+```
+
+The mail body contains the timestamp and the contents of `backup.log`. This only
+covers `backup.sh` failures — a *missed* run (host down, cron removed) is not
+detected, so monitor the PBS side too.
+
 Encryption is client-side. The key file has no password (`kdf: none`), so
 **possession of the key file alone is enough to decrypt** — protect it.
 

backup.env.sample

@@ -27,3 +27,6 @@ ENCRYPTION_KEY_FILE="/opt/backup/encryption-key.pem"
 
 # --- Local hostname (used as backup-id and archive-name prefix) ---
 HOSTNAME="$(hostname)"
+
+# --- Failure notification (email sent on backup failure; empty = disabled) ---
+NOTIFY_EMAIL="admin@example.com"

backup.sh

@@ -10,6 +10,7 @@ source "$SCRIPT_DIR/backup.env"
 # ==============================================================================
 BACKUP_LABEL="${HOSTNAME}-root"
 EXCLUDE_FILE="/opt/backup/exclude"
+LOG_FILE="${SCRIPT_DIR}/backup.log"
 
 # ==============================================================================
 # EXECUTION
@@ -27,9 +28,24 @@ while IFS= read -r line; do
     EXCLUDE_ARGS+=(--exclude "$line")
 done < "$EXCLUDE_FILE"
 
-proxmox-backup-client backup "${BACKUP_LABEL}.pxar:/" \
+if proxmox-backup-client backup "${BACKUP_LABEL}.pxar:/" \
     --keyfile "$ENCRYPTION_KEY_FILE" \
     --ns "$BACKUP_NS" \
-    "${EXCLUDE_ARGS[@]}"
-
-echo "Backup completed successfully!"
+    "${EXCLUDE_ARGS[@]}" 2>&1 | tee "$LOG_FILE"; then
+    echo "Backup completed successfully!"
+else
+    echo "Backup FAILED — see $LOG_FILE" >&2
+    if [ -n "${NOTIFY_EMAIL:-}" ]; then
+        {
+            echo "To: $NOTIFY_EMAIL"
+            echo "From: root@${HOSTNAME}"
+            echo "Subject: [pbs-backup] FAILED on ${HOSTNAME}"
+            echo
+            echo "The Proxmox backup on ${HOSTNAME} failed at $(date -R)."
+            echo
+            echo "--- backup log ---"
+            cat "$LOG_FILE"
+        } | sendmail -t
+    fi
+    exit 1
+fi

setup.sh

@@ -107,6 +107,10 @@ EOF
 systemctl daemon-reload
 systemctl enable --now pbs-backup.timer
 
+# 8. Hardening: deny read/write/execute to "others" for everything in /opt/backup
+#    (including the directory itself), so config and backups are not world-readable.
+chmod -R o-rwx "$BACKUP_DIR"
+
 echo
 echo "Done. Fill in the credentials, then run ${BACKUP_DIR}/backup.sh (or wait for the timer):"
 echo "    ${EDITOR:-vi} ${ENV_FILE}   # server/datastore/namespace/token"