Add backup service image (Dockerfile, entrypoint, crontab)

backup/Dockerfile

@@ -0,0 +1,11 @@
+FROM alpine:3.20
+
+RUN apk add --no-cache restic postgresql16-client curl tzdata dcron tar bash
+
+COPY backup/backup.sh /backup.sh
+COPY backup/entrypoint.sh /entrypoint.sh
+COPY backup/crontab /etc/crontabs/root
+
+RUN chmod +x /backup.sh /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]

backup/backup.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+set -euo pipefail
+exit 0

backup/crontab

@@ -0,0 +1,2 @@
+0 3 * * * /backup.sh >> /proc/1/fd/1 2>&1
+0 4 * * 0 restic check >> /proc/1/fd/1 2>&1

backup/entrypoint.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+set -euo pipefail
+
+if ! restic snapshots >/dev/null 2>&1; then
+  restic init
+fi
+
+exec crond -f -l 2