source in every Dockerfile RUN call

Question

I have a Dockerfile, where I am finding myself constantly needing to call source /opt/ros/noetic/setup.bash.

e.g.:

RUN source /opt/ros/noetic/setup.bash \
    && SOME_COMMAND

RUN source /opt/ros/noetic/setup.bash \
    && SOME_OTHER_COMMAND

Is there a method to have this initialised in every RUN call in a Dockerfile?

Have tried adding to ~/.bash_profile and Docker's ENV command with no luck.

Answer 1

TL;DR: what you want is feasible by copying your .sh script in /etc/profile.d/ and using the SHELL Dockerfile command to tweak the default shell.

Details:

To start with, consider the following sample script setup.sh:

#!/bin/sh
echo "# setup.sh"
ENV_VAR="some value"
some_fun() {
    echo "## some_fun"
}

Then, it can be noted that bash provides the --login CLI option:

When Bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. The --noprofile option may be used when the shell is started to inhibit this behavior.

When an interactive login shell exits, or a non-interactive login shell executes the exit builtin command, Bash reads and executes commands from the file ~/.bash_logout, if it exists.

− https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Bash-Startup-Files

Furthermore, instead of appending the setup.sh code in /etc/profile, you can take advantage of the /etc/profile.d folder that is read in the following way by most distributions:

$ docker run --rm -i debian:10 cat /etc/profile | tail -n 9

if [ -d /etc/profile.d ]; then
  for i in /etc/profile.d/*.sh; do
    if [ -r $i ]; then
      . $i
    fi
  done
  unset i
fi

Note in particular that the .sh extension is mandatory, hence the naming of the minimal-working-example above: setup.sh (not setup.bash).

Finally, it is possible to rely on the SHELL command to replace the default shell used by RUN (in place of ["/bin/sh", "-c"]) to incorporate the --login option of bash.

Concretely, you could phrase your Dockerfile like this:

FROM debian:10

# WORKDIR /opt/ros/noetic
# COPY setup.sh .
# RUN . /opt/ros/noetic/setup.sh && echo "ENV_VAR=$ENV_VAR"

# empty var here
RUN echo "ENV_VAR=$ENV_VAR"

# enable the extra shell init code
COPY setup.sh /etc/profile.d/

SHELL ["/bin/bash", "--login", "-c"]

# nonempty var and function
RUN echo "ENV_VAR=$ENV_VAR" && some_fun

# DISABLE the extra shell init code!
RUN rm /etc/profile.d/setup.sh

# empty var here
RUN echo "ENV_VAR=$ENV_VAR"

Outcome:

$ docker build -t test .
Sending build context to Docker daemon  6.144kB
Step 1/7 : FROM debian:10
 ---> ef05c61d5112
Step 2/7 : RUN echo "ENV_VAR=$ENV_VAR"
 ---> Running in 87b5c589ec60
ENV_VAR=
Removing intermediate container 87b5c589ec60
 ---> 6fdb70be76f9
Step 3/7 : COPY setup.sh /etc/profile.d/
 ---> e6aab4ebf9ef
Step 4/7 : SHELL ["/bin/bash", "--login", "-c"]
 ---> Running in d73b0d13df23
Removing intermediate container d73b0d13df23
 ---> ccbe789dc36d
Step 5/7 : RUN echo "ENV_VAR=$ENV_VAR" && some_fun
 ---> Running in 42fd1ae14c17
# setup.sh
ENV_VAR=some value
## some_fun
Removing intermediate container 42fd1ae14c17
 ---> de74831896a4
Step 6/7 : RUN rm /etc/profile.d/setup.sh
 ---> Running in bdd969a63def
# setup.sh
Removing intermediate container bdd969a63def
 ---> 5453be3271e5
Step 7/7 : RUN echo "ENV_VAR=$ENV_VAR"
 ---> Running in 0712cea427f1
ENV_VAR=
Removing intermediate container 0712cea427f1
 ---> 216a421f5659
Successfully built 216a421f5659
Successfully tagged test:latest