Add readme.

README.md

@@ -0,0 +1,39 @@
+# Docker Volume Backup
+
+A simple script which creates tarballs from docker volumes and restores
+them.
+
+## Usage
+
+### Backup a single volume
+
+`./dvbackup.sh backup <volume_name> <path/to/tarball.tar>`
+
+Creates a tarball from the contents of the volume.
+
+### Restore a single volume
+
+`./dvbackup.sh restore <path/to/tarball.tar> <volume_name>`
+
+Restores the tarball into the volume. *This is destructive*, all old
+contents will be removed from the volume. The volume must already exist.
+
+### Backup all named volumes
+
+`./dvbackup.sh backup_all`
+
+Creates backups from all volumes which do not only contain the character
+set `[0-9a-f]`.
+
+This command will output a `<volume_name>.tar` file for every found
+volume in the current working directory.
+
+### Restore volumes
+
+`./dvbackup.sh restore_all [volume.tar...]`
+
+Restores all given tarballs into their respective volumes. The volumes
+must already exist and the operation is *destructive* in the same way
+as the `restore` operation. The default behaviour is to ask before
+continuing, this can be overridden by setting `DVB_I_KNOW_WHAT_I_DO=y`.
+Volumes can be created implicitly by setting `DVB_CREATE_VOLUME=y`.

dvbackup.sh

@@ -1,50 +1,81 @@
-#!/usr/bin/env bash
+#!/usr/bin/env sh
+
+if [ -z "$DOCKER" ]; then
+    DOCKER=docker
+fi
+
+
+echo_and_run() {
+    echo "$@"
+    "$@"
+    return $?
+}
 
 backup() {
-    local volume
-    local target
-    local target_dir
-    local target_name
     volume="$1"
     target="$(realpath "$2")"
     target_dir="$(dirname "$target")"
     target_name="$(basename "$target")"
 
-    test -z "$(docker volume ls | grep "$volume")" && { echo "Error: No such volume, aborting" >&2; exit 1; }
+    test -z "$("$DOCKER" volume ls | grep "$volume")" && { echo "Error: No such volume, aborting" >&2; exit 1; }
     test -z "$target_dir" && { echo "Error: No base folder found for target=$target" >&2; exit 2; }
     test -z "$target_name" && { echo "Error: No target name found for target=$target" >&2; exit 3; }
 
-    set -x
+    echo_and_run "$DOCKER" run --rm \
-    docker run --rm --mount="type=volume,source=$volume,destination=/data,ro=true" --mount="type=bind,source=$target_dir,destination=/data2" busybox /bin/sh -c "tar cvf '/data2/$target_name' /data && chown $(id -u):$(id -g) /data2/$target_name"
+        --mount="type=volume,source=$volume,destination=/data,ro=true" \
-    set +x
+        --mount="type=bind,source=$target_dir,destination=/data2" \
+        busybox /bin/sh -c \
+        "cd /data/ && tar cf '/data2/$target_name' ./* && chown $(id -u):$(id -g) /data2/$target_name"
 }
 
 restore() {
-    local volume
-    local target
-    local target_dir
-    local target_name
     target="$(realpath "$1")"
     target_dir="$(dirname "$target")"
     target_name="$(basename "$target")"
     volume="$2"
 
-    test -z "$(docker volume ls | grep "$volume")" && { echo "Error: No such volume, aborting" >&2; exit 1; }
+    test -z "$("$DOCKER" volume ls | grep "$volume")" && { echo "Error: No such volume, aborting" >&2; exit 1; }
     test -z "$target_dir" && { echo "Error: No base folder found for target=$target" >&2; exit 2; }
     test -z "$target_name" && { echo "Error: No target name found for target=$target" >&2; exit 3; }
 
-    set -x
+    echo_and_run "$DOCKER" run --rm \
-    docker run --rm --mount="type=volume,source=$volume,destination=/data" --mount="type=bind,source=$target_dir,destination=/data2" busybox /bin/sh -c "rm -rf /data/* && cd / && tar xvf '/data2/$target_name'"
+        --mount="type=volume,source=$volume,destination=/data" \
-    set +x
+        --mount="type=bind,source=$target_dir,destination=/data2" \
+        busybox /bin/sh -c \
+        "cd /data/ && rm -rf ./* && tar xf '/data2/$target_name'"
 }
 
-main() {
+backup_all() {
-    local volumes
+    "$DOCKER" volume ls \
-    volumes="$(docker volume ls | tail -n+2 | egrep -v '[a-z]+\s+[0-9a-f]+$' | egrep -o '\s.+$' | sed 's/\s//g')"
+            | awk '!/^[a-z]+ +[0-9a-f]+$/ && (NR>1) {print $2}' \
-    while read -r line; do
+            | while read -r volume_name; do
-        echo "$line -> $line.tar"
+        echo "$volume_name -> $volume_name.tar"
-        backup "$line" "$line.tar"
+        backup "$volume_name" "$volume_name.tar"
-    done <<< "$volumes"
+    done
+}
+
+restore_all() {
+    if [ -z "$DVB_I_KNOW_WHAT_I_DO" ]; then
+        printf "The following operation will delete all data in the volumes to be restored, are you sure [y/N]? "
+        read -r DVB_I_KNOW_WHAT_I_DO
+    fi
+    if echo "$DVB_I_KNOW_WHAT_I_DO" | grep -Eviq 't|true|1|y|yes'; then
+        echo aborting
+        exit 1
+    fi
+    for tarball in "$@"; do
+        volume_name="${tarball%.tar}"
+        echo "$volume_name -> $volume"
+        if ! "$DOCKER" volume inspect "$volume_name" 1>&2 2>/dev/null; then
+            if echo "$DVB_CREATE_VOLUME" | grep -Eiq 't|true|1|y|yes'; then
+                "$DOCKER" volume create "$volume_name"
+            else
+                echo "Error: no such volume $volume_name" >&2
+                exit 4
+            fi
+        fi
+        restore "$tarball" "$volume_name"
+    done
 }
 
 "$@"

test/mock-docker.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env sh
+
+volume() {
+    if [ "$1" = 'ls' ]; then
+        echo "DRIVER VOLUME NAME"
+        echo "local 00c674e3f3c1587d88c2ebf2f91da5843b9dddb3e8df272898bdfd4e596aef79"
+        echo "local $DOCKER_MOCK_VOLUME"
+        return 0
+    elif [ "$2" = 'inspect' ]; then
+        if [ "$3" = "$DOCKER_MOCK_VOLUME" ]; then
+            return 0
+        else
+            return 1
+        fi
+    fi
+}
+
+
+if [ "$1" = "volume" ]; then
+    "$@"
+else
+    docker "$@"
+fi
+

test/test.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env sh
+
+
+cd "$(dirname "$0")" || exit 1
+
+VOLUME_NAME="$(dd if=/dev/random bs=6 count=1 | base64)"
+docker volume create "$VOLUME_NAME"
+
+# shellcheck disable=SC2064
+trap "docker volume rm $VOLUME_NAME && rm -f $VOLUME_NAME.tar" EXIT
+
+docker run --rm --volume="$VOLUME_NAME:/data" alpine \
+    sh -c 'echo "test" > /data/a.txt'
+DOCKER=./mock-docker.sh DOCKER_MOCK_VOLUME="$VOLUME_NAME" \
+    ../dvbackup.sh backup_all
+stat "$VOLUME_NAME.tar" || exit 1
+docker run --rm --volume="$VOLUME_NAME:/data" alpine \
+    sh -c 'rm /data/a.txt' || exit 1
+DOCKER=./mock-docker.sh DOCKER_MOCK_VOLUME="$VOLUME_NAME" \
+    ../dvbackup.sh restore_all "$VOLUME_NAME.tar" || exit 1
+docker run --rm --volume="$VOLUME_NAME:/data" alpine \
+    sh -c 'stat /data/a.txt' || exit 1
+exit 0