First version

Dockerfile

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+# docker-duplicity-backup
+#
+# Copyright (C) 2021  Pini <gilles.filippini -@- pini.fr>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+FROM debian
+
+RUN apt-get update && \
+    DEBIAN_FRONTEND=noninteractive apt-get -y install \
+      openssh-client \
+      stunnel4 \
+      rsync \
+      duplicity
+
+ENTRYPOINT ["docker-entrypoint.sh"]
+WORKDIR /root
+CMD ["do_backup"]
+
+COPY bin/* /usr/local/bin/
+
+VOLUME /root/.cache/duplicity
+RUN mkdir init.d

README.md

@@ -1,3 +1,19 @@
 # docker-duplicity-backup
 
-Docker container and script to backup a list of docker volumes to a remote duplicity target.
+Docker container and script to backup a list of docker volumes to a remote duplicity target.
+
+## Usage
+
+```
+$ ./docker-duplicity-backup <config_file>
+```
+
+The `config_file` parameter is mandatory and must designate a script file which set these variables:
+ * `DOCKER_HOSTNAME`: hostname used for the container running the backup (optional; defaults to '`backup`')
+   This hostname should be the same through incremental backups or duplicity will complain
+ * `VOLUMES`: space separated lit of volumes to backup
+ * `DUPLICITY_REMOTE_URI`: target URI for duplicity backup (mandatory; e.g. 'rsync://backup.example.com//target/path')
+ * `DUPLICITY_CACHE_VOLUME`: docker volume name to use for duplicity cache persistency (optional; default to '`backup_cache`')
+ * `INIT_FOLDER`: local path to mount into the container as `/root/init.d` (optional)
+   The scripts into this folder will be sourced by the container's entrypoint before starting the backup. Useful for starting an `stunnel` service
+ * `DOCKER_EXTRA_OPTIONS`: docker run options such as environment variables or extra volumes. Useful for importing an ssh configuration folder

bin/do_backup

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+#!/bin/bash
+# docker-duplicity-backup
+#
+# Copyright (C) 2021  Pini <gilles.filippini -@- pini.fr>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+month_start=$(date -Iseconds | sed 's/..T..:..:../01T00:00:00/')
+
+function backup_volume () {
+  local volume="$1"
+  duplicity --no-encryption --full-if-older-than "$month_start" --file-prefix "$volume." /volumes/$volume "$DUPLICITY_REMOTE_URI"
+}
+
+for volume in $VOLUMES; do
+  echo "Backuping volume '$volume'..."
+  backup_volume $volume
+done

bin/docker-entrypoint.sh

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+#!/bin/bash
+# docker-duplicity-backup
+#
+# Copyright (C) 2021  Pini <gilles.filippini -@- pini.fr>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+for file in $(ls init.d); do
+  if [ -x init.d/$file ]; then
+    ./init.d/$file
+  fi
+done
+
+if [ $# -gt 0 ]; then
+  exec "$@"
+else
+  exec /bin/bash -l
+fi

docker-duplicity-backup

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+#!/bin/bash
+# docker-duplicity-backup
+#
+# Copyright (C) 2021  Pini <gilles.filippini -@- pini.fr>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+set -euo pipefail
+
+function usage () {
+  echo "Usage: $(basename "$0") <config_file>"
+}
+
+conf_file="$1"
+if [ -z "$conf_file" ]; then
+  usage >&2
+  exit 1
+fi
+
+if ! [ -f "$conf_file" ]; then
+  echo "Missing configuration file '$conf_file'" >&2
+  exit 2
+fi
+
+echo "Sourcing configuration file '$conf_file'..."
+source "$conf_file"
+
+echo "Running docker-duplicity-backup using this configuration:
+DOCKER_HOSTNAME='${DOCKER_HOSTNAME:-}'
+VOLUMES='$VOLUMES'
+DUPLICITY_REMOTE_URI='$DUPLICITY_REMOTE_URI'
+DUPLICITY_CACHE_VOLUME='${DUPLICITY_CACHE_VOLUME:-}'
+INIT_FOLDER='${INIT_FOLDER:-}'
+DOCKER_EXTRA_OPTIONS='${DOCKER_EXTRA_OPTIONS[@]:-}'
+"
+
+DOCKER_HOSTNAME="${DOCKER_HOSTNAME:-docker-duplicity-backup}"
+DUPLICITY_CACHE_VOLUME="${DUPLICITY_CACHE_VOLUME:-backup_cache}"
+
+declare -a docker_mounts
+for volume in $VOLUMES; do
+  docker_mounts+=(-v "$volume:/volumes/$volume:ro")
+done
+
+if [ -n "$INIT_FOLDER" ]; then
+  docker_mounts+=(-v "$INIT_FOLDER":/root/init.d)
+fi
+
+docker run --rm -it \
+  --hostname "$DOCKER_HOSTNAME" \
+  -v "$DUPLICITY_CACHE_VOLUME":/root/.cache/duplicity \
+  "${docker_mounts[@]}" \
+  -e VOLUMES="$VOLUMES" \
+  -e DUPLICITY_REMOTE_URI="$DUPLICITY_REMOTE_URI" \
+  "${DOCKER_EXTRA_OPTIONS[@]:-\--}" \
+  pinidh/docker-duplicity-backup