Docker Container time & timezone (will not reflect changes)

Where do Docker containers get their time information? I've created some containers from the basic ubuntu:trusty image, and when I run it and request 'date', I get UTC time.

For awhile I got around this by doing the following in my Dockerfile:

RUN sudo echo "America/Los_Angeles" > /etc/timezone

However, for some reason that stopped working. Searching online I saw the below suggested:

docker run -v /etc/timezone:/etc/timezone [image-name]

Both these methods correctly set the timezone though!

$ cat /etc/timezone
America/Los_Angeles
$ date
Tue Apr 14 23:46:51 UTC 2015

Anyone know what gives?

Solution 1:

The secret here is that dpkg-reconfigure tzdata simply creates /etc/localtime as a copy, hardlink or symlink (a symlink is preferred) to a file in /usr/share/zoneinfo. So it is possible to do this entirely from your Dockerfile. Consider:

ENV TZ=America/Los_Angeles
RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone

And as a bonus, TZ will be set correctly in the container as well.

This is also distribution-agnostic, so it works with pretty much any Linux.

Note: if you are using an alpine based image you have to install the tzdata first. (see this issue here)

Looks like this:

RUN apk add --no-cache tzdata
ENV TZ America/Los_Angeles

Solution 2:

Usually it is sufficient to set an environment variable in the docker container, like so:

docker run -e TZ=Europe/Amsterdam debian:jessie date

Of course this would work also with docker-compose.

Solution 3:

You can add your local files (/etc/timezone and /etc/localtime) as volume in your docker-container.

Update your docker-compose.yml with the following lines.

volumes:
    - "/etc/timezone:/etc/timezone:ro"
    - "/etc/localtime:/etc/localtime:ro"

Now the container time is the same as on your host

Solution 4:

Mounting /etc/localtime in the image, so it is in sync with host -v is the most popular one.

But see issue 12084:

it is not correct because it does not work when the software requires instead the file /etc/timezone to be set.
That way you are using leaves it as the default value etc/UTC.

I have determined that actually there is no foolproof elegant way to set the time zone inside of a docker container.
So have finally settled on this solution:

App dockerfile:

# Relocate the timezone file
RUN mkdir -p /config/etc && mv /etc/timezone /config/etc/ && ln -s /config/etc/timezone /etc/

App entrypoint script:

# Set timezone as specified in /config/etc/timezone
dpkg-reconfigure -f noninteractive tzdata

Data volume /config dockerfile, localized to a specific country or region:

# Set the time zone
RUN echo "Europe/London" > /config/etc/timezone

... it is not elegant because involving 3 separate files, and re-creating /etc/localtime on every runtime container start. Which is rather wasteful.

However it does work properly, and successfully achieve separation between the base app image, and each per-country localized configuration.
In 3 lines of code.