Docker compose timezone bug

[FrizbySVK]

Hi, when running project with docker compose, timezone isn't evaluated correctly when backup is started.
Right now, I'm UTC+2 and backups are made at UTC time. So basically 2 hours later than I defined.

• host timezone info (Europe/Bratislava) is mounted as readonly volume as per config reference
• docker logs show the right time when debug is set to true. Same directly in the container. Time is correct
• here's a snippet of my docker-compose.yml:

  db_backup:
    image: databack/mysql-backup:1.5.0
    container_name: "${CONTAINER_PREFIX}_db_backup"
    restart: always
    volumes:
      - ./_db_backup/dataBackup:/db
      - ./_db_backup/_dataImport:/dataImport
      - ./_db_backup/scriptC/pre-backup:/scripts.d/pre-backup
      - ./_db_backup/scriptC/post-backup:/scripts.d/post-backup
      - ./_db_backup/log:/var/log/db-backup
      # use host timezone info
      - /etc/localtime:/etc/localtime:ro
      - /etc/timezone:/etc/timezone:ro
      - /usr/share/zoneinfo:/usr/share/zoneinfo:ro
    environment:
      - DB_SERVER=db
      - DB_PORT=3306
      - DB_USER=${DB_USER}
      - DB_PASS=${DB_PASSWORD}
      - DB_DUMP_TARGET=/db
      - DB_DUMP_BEGIN=0400
      - DB_DUMP_FREQ=1440
      - DB_DUMP_INCLUDE=${DB_NAMES_BACKUP}
      - LOG=/var/log/db-backup/Cron__1d__0400__15min__backupDb.log
      - LOG_DETAIL=/var/log/db-backup/Cron_1d__backupDb_detail.log
      - LOG_ERROR=/var/log/db-backup/backupDb.error.log
      - DB_DEBUG=true
    working_dir: /db
    command: dump
    user: "0" #root
    depends_on:
      db:
        condition: service_healthy

Docker logs of the image when it's started (UTC+2 so it's correct:

time="2026-08-17T09:00:09+02:00" level=debug msg="starting dump"

Containter time:

0faca8e5b026:/db# date
Tue Aug 18 06:48:05 CEST 2026
0faca8e5b026:/db# cat /etc/timezone 
Europe/Bratislava

Only option is to rebuild the image with overridden Dockerfile like this:

FROM databack/mysql-backup:1.5.0

USER root

RUN apk update && apk add tzdata logrotate && \
  ln -s /usr/share/zoneinfo/Europe/Bratislava /etc/localtime

# original entrypoint
ENTRYPOINT ["/entrypoint"]

So if I do it like this, it works. Mounting timezone info directly in compose file is not working for the purposes of backup scheduling.

Thank you

[deitch]

Hi @FrizbySVK this looks similar to the (automatically closed due to inactivity) issue #509. That had an engaging discussion on it, but a month went by without response, so it became stale, and a few weeks later closed out. If that is the exact same issue, let's reopen that and continue the discussion there?

In any case, please see your thoughts on my comments on it there.

[FrizbySVK]

Hi @deitch thank you for your response. I'd be happy to reopen issue #509 as you suggested. I think it's important to solve it because then we have to calcualte tz offset manually. Thank you