The question is "When we use the ENV instruction in the dockerfile, can we can keep it in the environment after the container is built?"

Dockerfile ENV

FROM nvcr.io/nvidia/tensorrt:20.03-py3

ENV TEST_PAR=TEST_dockerfile_env

Discuss about the ENV instruction of Dockerfile

The question is "When we use the ENV instruction in the dockerfile, can we can keep it in the environment after the container is built?"

The answer is YES.

Here is a simple dockerfile about the ENV instruction.

FROM nvcr.io/nvidia/tensorrt:20.03-py3

ENV TEST_PAR=TEST_dockerfile_env

Let's build it.

docker build -t test:test .
Sending build context to Docker daemon  2.048kB
Step 1/2 : FROM nvcr.io/nvidia/tensorrt:20.03-py3
20.03-py3: Pulling from nvidia/tensorrt
Digest: sha256:3ae126dc166475795d2481938367ffc574aae52937eda5337e588367b12c09ed
Status: Downloaded newer image for nvcr.io/nvidia/tensorrt:20.03-py3
 ---> 3132ca723421
Step 2/2 : ENV TEST_PAR=TEST_dockerfile_env
 ---> Running in 08218f56550e
Removing intermediate container 08218f56550e
 ---> ccbd89fb9fa5
Successfully built ccbd89fb9fa5
Successfully tagged test:test

Check it in docker images

docker images
REPOSITORY                       TAG                      IMAGE ID            CREATED             SIZE
test                             test                     ccbd89fb9fa5        19 seconds ago      4.08GB

Run it.

docker run --runtime nvidia -it --name=test_env test:test /bin/bash

=====================
== NVIDIA TensorRT ==
=====================

NVIDIA Release 20.03 (build 10567415)

NVIDIA TensorRT 7.0.0 (c) 2016-2020, NVIDIA CORPORATION.  All rights reserved.
Container image (c) 2020, NVIDIA CORPORATION.  All rights reserved.

https://developer.nvidia.com/tensorrt

To install Python sample dependencies, run /opt/tensorrt/python/python_setup.sh

To install open source parsers, plugins, and samples, run /opt/tensorrt/install_opensource.sh. See https://github.com/NVIDIA/TensorRT/tree/20.03 for more information.

root@941a3e33c77e:/workspace# ls
README.md  tensorrt
root@941a3e33c77e:/workspace# echo $TEST_PAR
TEST_dockerfile_env

I also did another test which is using export directly and exit this container, and then login again.

root@941a3e33c77e:/workspace# export test1111=test1111
root@941a3e33c77e:/workspace# echo $test1111
test1111
root@941a3e33c77e:/workspace# exit
exit

$ docker start test_env
test_env
$ docker exec -ti test_env /bin/bash
root@941a3e33c77e:/workspace# ls
README.md  tensorrt
root@941a3e33c77e:/workspace# echo $test1111

root@941a3e33c77e:/workspace# exit
exit

Conclusion

In the past, I was thinking the ENV instruction will only be used in the process of building the image by dockerfile.
The reason is that I misunderstand that ENV is equivalent to export because we all know that export is able to be only used once if we don't write the export in the .bashrc file.

Hence, I did this simple experiment to prove it.

for arm device

sudo sed -i'' 's/ports\.ubuntu\.com\/ubuntu-ports/free\.nchc\.org\.tw\/ubuntu-ports/' /etc/apt/sources.list