In their official site (https://docs.docker.com/reference/builder/#env), Docker support state that:
The ENV instruction sets the environment variable to the value
. This value will be passed to all future RUN instructions.
This is functionally equivalent to prefixing the command with < key >=< value >
I tried:
http_proxy=<PROXY> docker build .
However, this doesn't seem to bring the same effect as adding ENV http_proxy=< PROXY > inside the Dockerfile. Why ???
This is functionally equivalent to prefixing the command with < key >=< value >
This does not mean it is the same as prefixing docker build command since It is command executed outside of a container.
It means using ENV is the same as prefixing commands that run inside container.
For example, equivalent RUN statement would look like this:
RUN http_proxy=<PROXY> curl https://www.google.com
Or equivalent command executed inside container (via shell):
$ http_proxy=<PROXY> curl https://www.google.com
Related
I want to run a command, eval $(envkey-source) for setting certain environment variables using envkey. I install it, set my ENVKEY variable and then try to import all the environment variables. I do this all via Docker. However, docker is giving an error in this command:
Step 31/35 : RUN eval $(envkey-source)
---> Running in 6a9ebf1ede96
/bin/sh: 1: export: : bad variable name
The command '/bin/sh -c eval $(envkey-source)' returned a non-zero code: 2
I tried reading the documentation of envkey but they tell nothing about Docker.
I have installed envkey using following commands:
ENV ENVKEY=yada_yada
RUN curl -s https://raw.githubusercontent.com/envkey/envkey-source/master/install.sh | bash
Until here, all goes well. I get verbose of suggestions on the console about how to run the envkey to get all the environment variables set.
The problem comes on this side:
RUN eval $(envkey-source)
The error:
Step 31/35 : RUN eval $(envkey-source)
---> Running in 6a9ebf1ede96
/bin/sh: 1: export: : bad variable name
The command '/bin/sh -c eval $(envkey-source)' returned a non-zero code: 2
You can't do this, for a couple of reasons. The envkey documentation eventually links to an example in their GitHub which you might find informative.
Each Dockerfile RUN command runs a new shell in a new container. In particular, environment variables set within a RUN command are lost after it exits. Any form of RUN export ... is a no-op. If variables are static you can set them using the ENV directive, but in this case where you're running a program that needs to generate them dynamically, you need another approach.
A typical pattern here is to use a shell script as your container's ENTRYPOINT. That does some initial setup and then replaces itself with the container's CMD. Since the CMD runs in the same shell environment as the rest of the script, you can do dynamic variable setup here. The script might look like:
#!/bin/sh
eval "$(envkey-source)"
exec "$#"
The other thing to keep in mind here is that anyone can docker inspect your image and get its environment variables back out, or docker run imagename /usr/bin/env. If you could run envkey-source in the Dockerfile then the environment variables would be available in the image in clear text, which defeats the purpose. Even embedding the key in the image effectively leaks it. You should pass this at runtime using a docker run -e option or a Docker Compose environment: key, relaying it from the host's environment.
Is there a way we can pass a variable lets say in this example I want to pass a list of animals into an entrypoint.sh file using ENV animals="turtle, monkey, goose"
But I want to be able to pass different animals when running the container for example docker run -t image animals="mouse,rat,kangaroo"
How do you go about passing arguments when running the docker run command?
The goal is to take that variable when using the docker run command and insert them into that entrypoint.sh file
Right now i hard code that in my Dockerfile. But i want to be able to do this when running the docker run command so I dont always have to change the Dockerfile.
FROM anapsix/alpine-java:8u121b13_jdk
ENV FILE_NAME="file_to_run.zip"
ENV animals="turtle, monkey, goose"
ADD ${FILE_NAME} .
RUN echo "${FILENAME} ${animals}" > ./entrypoint.sh
CMD [ "/bin/ash", "./entrypoint.sh" ]
It looks like you might be confusing the image build with the container run. If the difference between the two isn't immediately clear, I'd recommend reviewing some other questions and docs like:
In Docker, what's the difference between a container and an image?
https://docs.docker.com/develop/develop-images/dockerfile_best-practices/
RUN echo "${FILENAME} ${animals}" > ./entrypoint.sh
With the above, the variables will be expanded during the image build. The entrypoint.sh will not contain ${FILENAME} ${animals}. Instead, it will contain
file_to_run.zip turtle, monkey, goose
After the build, the docker run command will create a container from that image and run the above script with the environment variables defined but never used since the script already has the variables expanded. To prevent the variable expansion, you need to escape the $ or use single quotes to prevent the expansion, e.g.
RUN echo "\${FILENAME} \${animals}" > ./entrypoint.sh
or
RUN echo '${FILENAME} ${animals}' > ./entrypoint.sh
I would also recommend being explicit with a #!/bin/ash at the top of this script. Then when you run the script, do not override the command with parameters after the image name. Instead set the environment variables with the appropriate flag to run:
docker run -it -e animals="mouse,rat,kangaroo" image
Simplest way, forward individual variables:
docker run ... --env animals="turtle, monkey, goose" --env FILE_NAME="file_to_run.zip"
Forward several variables using file:
Or if you need to grab all your environment variables from outside, you can do something like this first:
printenv | grep -E 'animals|FILE_NAME' > my-env
The grep is because Docker doesn't like some variables, e.g. with spaces in them, which you might possibly have in your real environment.
Then use that file in your Docker command:
docker run ... --env-file ./my-env
The latter is also useful if you want to avoid sending environment variables to logs (like for sensitive variables). I use this approach in a CI/CD pipeline that runs some scripts.
Using variables inside Docker:
With either approach, the environment variables actually become available to scripts running inside the container to use.
#BMitch's answer has more complete details about how to achieve this in your case, where you have related logic in both build and execution.
Reference
See docs here.
I need to give an argument while running Docker Image which will be a number from 0-3.
Dockerfile has the following:
WORKDIR "mydir/build"
CMD ./maker oneapp > /artifacts/oneapp_$1.log ; ./maker twoapp > /artifacts/twoapp_$1.log ; ./maker -j13 threeapp > /artifacts/threeapp_$1.log
I will be running the same Docker Image multiple times so I need logs to be saved in /artifacts appended with _0, _1, _2, _3, as appropriate.
I tried keeping this in Docker file but don't want to pass this full line as argument while running docker.
ENTRYPOINT ["/bin/bash"]
./maker oneapp > /artifacts/oneapp_$1.log ; ./maker twoapp >
/artifacts/twoapp_$1.log ; ./maker -j13 threeapp >
/artifacts/threeapp_$1.log
Is it possible to do this? What do I need to modify in Dockerfile to do what I want?
Simply inject your parameter as an ENV.
Declare an ENV in your Dockerfile.
ENV suffix 0
./maker oneapp > /artifacts/oneapp_${suffix}.log
The environment variables set using ENV will persist when a container is run from the resulting image.
You can view the values using docker inspect, and change them using docker run --env <key>=<value>.
That way, you can declare that ENV on docker run, and benefit from its value in the running container.
the operator can set any environment variable in the container by using one or more -e flags, even overriding those mentioned above, or already defined by the developer with a Dockerfile ENV:
In your case, for instance:
docker run -e suffix=2 <image_name>
I am running two python services inside docker. Both services require a common argument, which I provide during "docker run"
Currently, I am achieving this by calling both the services from a shell script. But, I think the proper solution would be using supervisor inside docker and run both the services through it.
I want to achieve something like this:
[program:A]
command=python -m A.py <argument>
[program:B]
command=python -m B.py <argument>
The dockerfile looks like this:
COPY supervisord.conf /etc/supervisor/conf.d/supervisord.conf
CMD ["/usr/bin/supervisord"]
How can I pass the argument to supervisor?
You could use an environment variable: from supervisor doc
Environment variables that are present in the environment at the time that supervisord is started can be used in the configuration file using the Python string expression syntax %(ENV_X)s:
[program:example]
command=/usr/bin/example --loglevel=%(ENV_LOGLEVEL)s
In the example above, the expression %(ENV_LOGLEVEL)s would be expanded to the value of the environment variable LOGLEVEL.
In your case, your common argument could be set in an environment variable passed to the container with a docker run -d -e "COMMON_ARG=myarg".
I need to fill a variable in dockerfile with the result of a command
Like in bash var=$(date)
EDIT 1
date is a example.
in my case i use FROM phusion/baseimage:0.9.17 so i want at each building use the last version so i use this
curl -v --silent api.github.com/repos/phusion/baseimage-docker/tags 2>&1 | grep -oh 'rel-.*",' | head -1 | sed 's/",//' | sed 's/rel-//' ==> 0.9.17.
but i don't know how i parse it in var with dockerfile for this result
ENV verbaseimage=curl...
FROM phusion/baseimage:$verbaseimage
RESULT
In my use case
FROM phusion/baseimage:latest
But the question remains unresolved for other case
I had same issue and found way to set environment variable as result of function by using RUN command in dockerfile.
For example i need to set SECRET_KEY_BASE for Rails app just once without changing as would when i run:
docker run -e SECRET_KEY_BASE="$(openssl rand -hex 64)"
Instead it i write to Dockerfile string like:
RUN bash -l -c 'echo export SECRET_KEY_BASE="$(openssl rand -hex 64)" >> /etc/bash.bashrc'
and my env variable available from root, even after bash login.
or may be
RUN /bin/bash -l -c 'echo export SECRET_KEY_BASE="$(openssl rand -hex 64)" > /etc/profile.d/docker_init.sh'
then it variable available in CMD and ENTRYPOINT commands
Docker cache it as layer and change only if you change some strings before it.
You also can try different ways to set environment variable.
The old workaround is mentioned here (issue 2637: Feature request: expand Dockerfile ENV $VARIABLES in WORKDIR):
One work around that I've used, is to have a file in my context called "build-env". What I do is source it and run my desired command in the same RUN step. So for example:
build-env:
VERSION=stable
Dockerfile:
FROM radial/axle-base:latest
ADD build-env /build-env
RUN source build-env && mkdir /$VERSION
RUN ls /
But for date, that might not be as precise as you want.
Other workarounds are in issue 2022 "Dockerfile with variable interpolation".
In docker 1.9 (end of October 2015), you will have "support for build-time environment variables to the 'build' API (PR 9176)" and "Support for passing build-time variables in build context (PR 15182)".
docker build --build-arg=[]: Set build-time variables
You can use ENV instructions in a Dockerfile to define variable values. These values persist in the built image. However, often persistence is not what you want. Users want to specify variables differently depending on which host they build an image on.
A good example is http_proxy or source versions for pulling intermediate files. The ARG instruction lets Dockerfile authors define values that users can set at build-time using the ---build-arg flag:
$ docker build --build-arg HTTP_PROXY=http://10.20.30.2:1234 .
This flag allows you to pass the build-time variables that are accessed like regular environment variables in the RUN instruction of the Dockerfile.
Also, these values don't persist in the intermediate or final images like ENV values do.
so I want at each building use the last version so I use this
curl -v --silent api.github.com/repos/phusion/baseimage-docker/tags 2>&1 | grep -oh 'rel-.*",' | head -1 | sed 's/",//' | sed 's/rel-//' ==> 0.9.17.
If you want to use the last version of that image, all you need to do is use the tag 'latest' with the FROM directive:
FROM phusion/baseimage:latest
See also "The misunderstood Docker tag: latest": it doesn't always reference the actual latest build, but in this instance, it should work.
If you really want to use the curl|parse option, use it to generate a Dockerfile with the right value (as in a template processed to generate the right file).
Don't try to use it directly in the Dockerfile.
I wanted to set an ENV or LABEL variable from a computation in the Dockerfile, e.g. to make some computed installation options visible in docker inspect.
There does not seem to be any way to do that, and this issue suggests that it's a security design choice.
A Dockerfile can set an ENV variable to $X, ${X:-default}, or ${X:+substitute} where that $X must be another ENV or ARG variable.
A single RUN command can set and use shell variables, but that goes away at the end of the RUN command when that container layer shuts down.
A RUN command can write computed data into files, but the Dockerfile still can't get that data into an ENV or LABEL even if the file is ~/.bashrc. (File contents can, of course, be used by code running in the Container.)
The build can at least RUN echo $X to record choices to the build log -- unless that step comes from the build cache, in which case the RUN step doesn't run.
Please do correct me if there's a way out.
Partially connected to question. If one wants to use the result of some command later on it is possible within single RUN statement as follows:
RUN CUR_DIR=`pwd` && \
echo $CUR_DIR