add tzdata package

[mmichalak-swe]

Changes

• Add tzdata package to Docker image

Reason

Installing tzdata provides the system timezone database and allows the container timezone to be configured via the TZ environment variable.

[m90]

I'm a bit torn on this one, mostly because of not wanting to change things that currently work as intended. I would definitely think this is something to include in a v3, yes.

One big question in here would be: considering this would be merged and users that currently mount their TZ data as it's done right now updated without changing their config, would their setups still continue to work?

[mmichalak-swe]

I just tested it by using my custom image (only adding tzdata to the existing v2.47.2 image), and commenting out the bind mounts:

environment:
  - TZ=${TZ}
image: offen/docker-volume-backup:v2.47.2-tzdata-test
volumes:
  # - /etc/timezone:/etc/timezone:ro
  # - /etc/localtime:/etc/localtime:ro
  # - /usr/share/zoneinfo:/usr/share/zoneinfo:ro

I also tried the custom image with tzdata added, against my old configuration (without a TZ variable, and with the bind mounts):

environment:
#   - TZ=${TZ}
image: offen/docker-volume-backup:v2.47.2-tzdata-test
volumes:
  - /etc/timezone:/etc/timezone:ro
  - /etc/localtime:/etc/localtime:ro
  - /usr/share/zoneinfo:/usr/share/zoneinfo:ro

I then tried using the custom tzdata image, with both configurations enabled together:

environment:
  - TZ=${TZ}
image: offen/docker-volume-backup:v2.47.2-tzdata-test
volumes:
  - /etc/timezone:/etc/timezone:ro
  - /etc/localtime:/etc/localtime:ro
  - /usr/share/zoneinfo:/usr/share/zoneinfo:ro

All cases are working as expected, producing the expected time with the date command, while also creating a local backup with the correct time. Additionally, this worked while stopping and starting a container to perform the backup. I understand your hesitation, but I think this is a low-risk change with a lot of upside. To set my timezone correctly, I had to read the documentation, and then follow the guidance given in #28. That is a lot of effort for what should be a simple setting, that some users might miss!

Perhaps it is better saved for v3, but I think this functionality could be enabled without issue immediately.

[m90]

To set my timezone correctly, I had to read the documentation, and then follow the guidance given in #28.

What info was missing from the docs that you could find in #28 only?

[mmichalak-swe]

From #28 (comment)

/usr/share/zoneinfo:/usr/share/zoneinfo:ro

Page it's missing from: set container timezone

services:
  backup:
    image: offen/docker-volume-backup:v2
    volumes:
      - data:/backup/my-app-backup:ro
      - /etc/timezone:/etc/timezone:ro
      - /etc/localtime:/etc/localtime:ro

volumes:
  data:

I can edit and open a PR to fix

[m90]

I can edit and open a PR to fix

That'd be grand 🎩

[mmichalak-swe]

Continuing our conversation here...

Thanks! I guess I'll need a little more time to ponder #748, I hope that's ok.

No worries. I can do some more testing and report back. I was doing some research on ChatGPT and it agrees that it's a low-risk change. I think the testing I did above will cover users that upgrade to a new image that includes tzdata, while their configuration may still contain the bind mounts (the bind mounts would take precedence). Let me know if there's anything else I can help you with on this.