# Linux – How to set localtime/timezone in the most generic and distro-agnostic way

centosdockerlinux

I've created a docker container, which is running in the wrong timezone. I personally need it to run in my timezone (Europe/Stockholm, GMT+1). Since the project is open source, other users may also wish to change that. I wish to make it easy for anyone to change this in e.g. the Dockerfile or in the docker-compose.yml.

If possible, I also wish that the solution is applicable not only on CentOS in case someone wishes to use a different distro.

What is the most distro-agnostic approach to set the localtime/timezone in my docker container?

These two approaches seem to be common but I'm not sure if they are really the best way forward for me:

### TZ environment variable

Some Linux distros read the TZ environment variable. However, I'm noticing it doesn't work when I use the centos:7 image.

### /etc/localtime

You can map the container's /etc/localtime to /etc/localtime on the host in the docker-compose.yml. But when doing this, distros that use /etc/timezone is left at UTC and software which may be reading that will then read the wrong timezone.

• Distro-agnostic would require a script that detects which distro is being used. This is because each distro "family" has a different way of noting timezones. For some, adding the following to the Dockerfile might work:

RUN echo "Europe/Stockholm" > /etc/timezone

Other (e.g., Debian) require using the above and then following with another Dockerfile command like:

RUN RUN sudo dpkg-reconfigure -f noninteractive tzdata

Other distros (IIRC, including CentOS) would require something like:

RUN ln -s /usr/share/zoneinfo/Europe/Stockhom /etc/localtime

Making it distro-agnostic would require researching each distro's method for re-configuring the timezone. If you look at /etc/localtime, you'll notice that it's not a text file.