Mbsync Docker

An opinionated set of simple Docker containers with Mbsync (Isync) and Supercronic.

Usage

Being slightly opinionated there isn't any ENTRYPOINT specified, instead only a default CMD to run Supercronic with the bundled /etc/crontab file that simply echoes a short message once a minute. This means you can easily change what the container does without having to override an ENTRYPOINT, and if you want to use the Supercronic functionality you only need to mount in your own crontab file at /etc/crontab and run the container without any additional args.

Docker Run

$ docker run --rm -it \
    -v $PWD/mbsyncrc:/workdir/.mbsyncrc \
    -v $PWD:/workdir/data \
    -w /workdir \
    cewood/mbsync:alpine_UPDATEME \
    mbsync --all --pull --create-slave --expunge-slave --verbose

Docker Compose

version: "3.4"
services:
  mbsync:
    image: cewood/mbsync:alpine_UPDATEME
    container_name: mbsync
    working_dir: /workdir
    volumes:
      - "/mnt/storage/containers/mbsync/data:/workdir/data"
      - "./mbsync/mbsyncrc:/workdir/.mbsyncrc"
      - "./mbsync/crontab:/etc/crontab"  # Be sure to update the crontab with your command(s)
    restart: unless-stopped
    labels:
      org.label-schema.group: "backups"

Image variants

Currently the following distributions are included:

• Alpine 3.12
• Debian 10.7 (Slim variant)
• Ubuntu 20.04 (LTS release)

Supported architectures

Currently the following architectures are built for each image variant:

• linux/amd64
• linux/arm64
• linux/arm/v7

Frequently Asked Questions

Why another Mbsync Docker Image

There was already a number of Mbsync/Isync images available on the Docker Hub, but unfortunately they all had their various short comings. Most weren't built via a Continuous Integration tool, none had any image tags, and none provided the Dockerfile or a link to their SCM tool of choice to inspect the image contents and build. Thus I decided to make my own set of images for Mbsync to address all these points, and here we are.

Why isn't the image named Isync

Great question! Since most people use Isync via the Mbsync command, I decided to name the image Mbsync, as this appears to be what most people search for and are familiar with. And the project itself states:

While isync is the project name, mbsync is the current executable name; this change was necessary because of massive changes in the user interface. An isync executable still exists; it is a compatibility wrapper around mbsync.

Why Supercronic and not just regular cron

If we were running a normal system in an interactive manner, then normal Cron or friends (Anacron, Fcron, etc) would be fine choices. However in a containerised environment, these traditional cron implementations have some downsides, that make Supercronic a better fit. Namely the printing of jobs output to stdout, hence when running Supercronic as the ENTRYPOINT/CMD I can see the output of the jobs being run without having to jump through any hoops. There are undoubtedly other features that Supercronic brings with it that make it a better fit for use in containers, but this was the main motivator for me.