Troubleshooting ‘apt-get install tzdata’ Hangs in Dockerfile on Ubuntu

When building Docker images on Ubuntu Server, you might encounter a common issue where the apt-get install tzdata command seems to hang indefinitely. This problem typically arises because the tzdata package installation process is interactive by default, prompting for geographical area and city selection. In a Dockerfile context, where there’s no interactive terminal, this prompt causes the build process to pause, waiting for input that will never come.

Let’s examine a typical scenario in a Dockerfile that leads to this hanging issue:

RUN apt-get install -y tzdata

During the Docker image build process, you might see output similar to this, indicating the system is waiting for interactive input:

Step 25/25 : RUN apt-get install -y tzdata
 ---> Running in ee47a1beff84
Reading package lists...
Building dependency tree...
Reading state information...
The following NEW packages will be installed:
  tzdata
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 189 kB of archives.
After this operation, 3104 kB of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 tzdata all 2018i-0ubuntu0.18.04 [189 kB]
debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
debconf: unable to initialize frontend: Readline
debconf: (This frontend requires a controlling tty.)
debconf: falling back to frontend: Teletype
dpkg-preconfigure: unable to re-open stdin:
Fetched 189 kB in 1s (219 kB/s)
Selecting previously unselected package tzdata.
(Reading database ... 25194 files and directories currently installed.)
Preparing to unpack .../tzdata_2018i-0ubuntu0.18.04_all.deb ...
Unpacking tzdata (2018i-2018i-0ubuntu0.18.04) ...
Setting up tzdata (2018i-0ubuntu0.18.04) ...
debconf: unable to initialize frontend: Dialog
debconf: (TERM is not set, so the dialog frontend is not usable.)
debconf: falling back to frontend: Readline
Configuring tzdata
------------------

Please select the geographic area in which you live. Subsequent configuration
questions will narrow this down by presenting a list of cities, representing
the time zones in which they are located.

 1. Africa      4. Australia  7. Atlantic  10. Pacific     13. Etc
 2. America     5. Arctic     8. Europe    11. SystemV
 3. Antarctica  6. Asia       9. Indian    12. US
Geographic area:

To resolve this, you need to ensure the tzdata installation is non-interactive. This can be achieved by pre-setting the DEBIAN_FRONTEND environment variable to noninteractive and using the -y flag with apt-get install to automatically answer “yes” to prompts. Here’s the corrected Dockerfile command:

ENV DEBIAN_FRONTEND=noninteractive
RUN apt-get install -y tzdata

By setting DEBIAN_FRONTEND=noninteractive, you instruct debconf (the Debian configuration management system) to avoid interactive prompts. The -y flag further suppresses any confirmation prompts from apt-get, ensuring a smooth, unattended installation process within your Dockerfile. This approach is crucial for automating Docker image builds, especially when deploying applications on Ubuntu servers where consistent and predictable builds are essential.