I’m setting up a docker container to just be a simple environment for Ocaml, since I don’t wanna have to manage two OPAM tool chains on two computers. (Windows desktop, Linux laptop) My goal is to have the container load in to a bash command prompt on docker-compose run with ocaml ready to go, and to do this I need to enter in to bash and then run eval $(opam env) on startup. This is my current docker file:
FROM ocaml/opam:alpine-3.12
# Create folder and assign owner
USER root
RUN mkdir /code
WORKDIR /code
RUN chown opam:opam /code
USER opam
# Install ocaml
RUN opam init
RUN opam switch create 4.11.1
RUN opam install dune
# bash env
CMD [ "/bin/bash" ]
ENTRYPOINT [ "eval", "\$(opam env)" ]
Building and trying to run this gives me the error:
sh: $(opam env): unknown operand
ERROR: 2
I tried making a run.sh script but that ran into some chmod/permission issues that are probably harder to debug than this. What do I do to open this container in bash and then run the eval $(opam env) command? I don’t want to do this with command line arguments, I’d like to do this all in a dockerfile or docker-compose file
The trick is to use opam exec1 as the entry point, e.g.,
ENTRYPOINT ["opam", "exec", "--"]
Then you can either run directly a command from the installed switch or just start an interactive shell with run -it --rm <cont> sh and you will have the switch fully activated, e.g.,
$ docker run -it --rm binaryanalysisplatform/bap:latest sh
$ which ocaml
/home/opam/.opam/4.09/bin/ocaml
As an aside, since we're talking about docker and OCaml, let me share some more tricks. First of all, you can look into our collection of dockerfiles in BAP for some inspiration. And another important trick that I would like to share is using multistage builds to shrink the size of the image, here's an example Dockerfile. In our case, it gives us a reduction from 7.5 Gb to only 750 Mb, while still preserving the ability to run and build OCaml programs.
And another side note :) You also should run your installation in a single RUN entry, otherwise your layers will eventually diverge and you will get weird missing packages errors. Basically, here's the Dockerfile that you're looking for,
FROM ocaml/opam2:alpine
WORKDIR /home/opam
RUN opam switch 4.11.1 \
&& eval "$(opam env)" \
&& opam remote set-url default https://opam.ocaml.org \
&& opam update \
&& opam install dune \
&& opam clean -acrs
ENTRYPOINT ["opam", "exec", "--"]
1)Or opam config exec, i.e., ENTRYPOINT ["opam", "config", "exec", "--"] for the older versions of opam.
There's no way to tell Docker to do something after the main container process has started, or to send input to the main container process.
What you can do is to write a wrapper script that does some initial setup and then runs whatever the main container process is. Since that eval command will just set environment variables, those will carry through to the main shell.
#!/bin/sh
# entrypoint.sh
# Set up the version-manager environment
eval $(opam env)
# Run the main container command
exec "$#"
In the Dockerfile, make this script be the ENTRYPOINT:
COPY entrypoint.sh /usr/local/bin
ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]
CMD ["/bin/bash"]
It also might work to put this setup in a shell dotfile, and run bash -l as the main container command to force it to read dotfiles. However, the $HOME directory isn't usually well-defined in Docker, so you might need to set that variable. If you expand this setup to run a full application, the entrypoint-wrapper approach will will there too, but that sequence probably won't read shell dotfiles at all.
What you show looks like an extremely straightforward installation sequence and I might not change it, but be aware that there are complexities around using version managers in Docker. In particular every Dockerfile RUN command has a new shell environment and the eval command won't "stick". I'd ordinarily suggest picking a specific version of the toolchain and directly installing it, maybe in /usr/local, without a version manager, but that approach will be much more complex than what you have currently. For more mainstream languages you can also usually use e.g. a node:16.13 prebuilt image.
What's with the error you're getting? For ENTRYPOINT and CMD (and also RUN) Docker has two forms. If something is a JSON array then Docker runs the command as a sequence of words, with one word in the array translating to one word in the command, and no additional interpretation or escaping. If it isn't a JSON array – even if it's mostly a JSON array, but has a typo – Docker will interpret it as a shell command and run it with sh -c. Docker applies this rule separately to the ENTRYPOINT and CMD, and then combines them together into a single command.
In particular in your ENTRYPOINT line, RFC 8259 §7 defines the valid character escapes in JSON, so \n is a newline and so on, but \$ is not one of those. That makes the embedded string invalid, and therefore the ENTRYPOINT line isn't valid, and Docker runs it via a shell. The single main container command is then
sh -c '[ "eval", "\$(opam env)" ]' '/bin/bash'
which runs the shell command [, as in if [ "$1" = yes ]; then ...; fi. That command doesn't understand the $(...) string as an argument, which is the error you're getting.
The JSON array already has escaped the things that need to be escaped, so it looks like you could get around this immediate error by removing the erroneous backslash
ENTRYPOINT ["eval", "$(opam env)"] # won't actually work
Docker will run this as-is, combining it with the CMD, and you get
'eval' '$(opam env)' '/bin/bash'
But eval isn't a "real" command – there is no /bin/eval binary – and Docker will pass on the literal string $(opam env) without interpreting it at all. That's also not what you want.
In principle it's possible to do this without writing a script, but you lose a lot of flexibility. For example, consider
# no ENTRYPOINT; shell-form CMD
CMD eval $(opam env) && exec /bin/bash
Again, though, if you replace this CMD with anything else you won't have done the initial setup step.
I have following Dockerfile:
FROM ubuntu:16.04
ARG path1=def_path1
RUN mkdir ${path1}
When I build this Dockerfile using following command:
docker build --build-arg path1=/home/dragan -t build_arg_ex .
I get following error when I execute it in MINGW bash on Windows 10:
$ ./build.sh --no-cache
Sending build context to Docker daemon 6.144kB
Step 1/3 : FROM ubuntu:16.04
---> 2a4cca5ac898
Step 2/3 : ARG path1=def_path1
---> Running in a35241ebdef3
Removing intermediate container a35241ebdef3
---> 01475e50af4c
Step 3/3 : RUN mkdir ${path1}
---> Running in 2759e683cbb1
mkdir: cannot create directory 'C:/Program': No such file or directory
mkdir: cannot create directory 'Files/Git/home/dragan': No such file or
directory
The command '/bin/sh -c mkdir ${path1}' returned a non-zero code: 1
Building same Dockerfile in Windows Command Prompt or on Linux or Mac is ok. The problem is only in MINGW bash terminal on Windows because it adds 'C:/Program Files/Git' before the path that is passed as argument.
Is there a way to execute this in MINGW bash so it does not add the 'C:/Program Files/Git' prefix?
Thanks
This is actually a bug/limitation of Git for Windows as described in the Release Notes under Known issues:
If you specify command-line options starting with a slash, POSIX-to-Windows path conversion will kick in converting e.g. "/usr/bin/bash.exe" to "C:\Program Files\Git\usr\bin\bash.exe". When that is not desired -- e.g. "--upload-pack=/opt/git/bin/git-upload-pack" or "-L/regex/" -- you need to set the environment variable MSYS_NO_PATHCONV temporarily, like so:
MSYS_NO_PATHCONV=1 git blame -L/pathconv/ msys2_path_conv.cc
Alternatively, you can double the first slash to avoid POSIX-to-Windows path conversion, e.g. "//usr/bin/bash.exe".
Further to #mat007's answer:
This bash function solved the problem more permanently for docker, without enabling MSYS_NO_PATHCONV globally, which causes another world of pain.
.bashrc
# See https://github.com/docker/toolbox/issues/673#issuecomment-355275054
# Workaround for Docker for Windows in Git Bash.
docker()
{
(export MSYS_NO_PATHCONV=1; "docker.exe" "$#")
}
You may need to do the same for docker-compose
So I am running a script that calls:
docker-compose run --rm web sh /data/bin/install_test_db.sh
and it seems to work fine when running it on ubuntu but when I run it on Windows using Git Bash I get this error:
sh: 0: Can't open C:/Program Files/Git/data/bin/install_test_db.sh
It seems to be trying to run the script on my machine and not the actual container from which I am trying to call it from.
Any ideas on why this is happening?
First, try passing a command to your sh shell:
docker-compose run --rm web sh -c "/data/bin/install_test_db.sh"
Or:
docker-compose run --rm web "sh -c /data/bin/install_test_db.sh"
That will avoid your host shell (the git bash) to interpret an absolute path (starting with '/') as one from the Git installation path.
That will keep /data/... as an argument to be passed to the shell executed in the container.
Note: If you are using Docker for Windows (meaning not VirtualBox, but HyperV), you don't need git bash at all.
Try the same command from a regular CMD (with docker.exe in your %PATH%, which Docker for Windows set for you)
vonc#VONCAVN7 C:\Users\vonc
> where docker
C:\Program Files\Docker\Docker\Resources\bin\docker.exe
If you need Linux-like commands from that same CMD session, then yes, add git paths:
set GH=C:\path\to\git
set PATH=%GH%\bin;%GH%\usr\bin;%GH%\mingw64\bin;%PATH%
I have some script that I need to run inside the container, and somehow it only run if I run it inside a bash --login.
I normally run my docker: docker build -t sometags . and I noticed it only run bash without --login.
I know I can just use bash -l -c "some-command-here" but I'd say it's my final fallback if nothing can helps.
so, tl;dr: how can I achieve something like this in my Dockerfile
#dockerfile
RUN bash --login
RUN some-script
and then, I'll just run it with: docker build -t x/y:z .
updated:
the scripts I want to run is things like: gem install bundler, and bundle install.
On OSX, when running a docker container and mounting the current directory, the expression $(pwd) does not get expanded:
bash
docker run -v $(pwd):/var/mydir image
On the container, /var/mydir remains empty.
I have installed bash-completion via homebrew, and the docker-specific bash completion also.
I see examples of using $(pwd) on OSX all over the place, and yet I cannot make it work.
Please note that the current directory is under /Users, e.g. /Users/joe/projects/demo
Try to test it first:
path=$(pwd); echo ${path}
If that work, then you can add the docker command:
path=$(pwd); docker run -v ${path}:/var/mydir image
Also, if you are executing that command from the host shell (Mac), instead of the docker machine shell (through a docker-machine ssh session), make sure you have executed eval "$(docker-machine env <machinename>)" first.
Using ${PWD}:
docker run -v ${PWD}:/src -w /src golang:1.17 go mod download && go run main.go