Running a docker image with a command line such as:
> docker run -it -v $OutsideDir:$InsideDir -u $(id -u):$(id -g) c0ffeebaba bash
I am able to work on my data as the current user on the host from inside the docker container. However, asking inside the container 'whoami' gives the response that the UID is unknown.
So the shell is executed on a user without a home-directory. How can I get some initialization being done for that user? Is there a way to map the user id and group id of an external user to a specific user name from inside? Can this be done dynamically, so that it would work for any user, specified through the '--user' flag as shown above?
My first approach would have been to use 'CMD' in the Dockerfile such as
CMD ["source", "/home/the_user/.bashrc" ]
But, that does not work.
A relatively simple solution would be to wrap the docker run in a script, mapping in the /etc/passwd and /etc/group files from the host onto the container, as well as the user's home directory, so something like:
#!/bin/bash -p
# command starts with mapping passwd and group files
cmd=(docker run -v /etc/passwd:/etc/passwd:ro -v /etc/group:/etc/group:ro)
# add home directory:
myhome=$(getent passwd $(id -nu) | awk -F: '{print $6}')
cmd+=(-v $myhome:$myhome)
# add userid and groupid mappings:
cmd+=(-u $(id -u):$(id -g))
# then pass through any other arguments:
cmd+=("$@")
"${cmd[@]}"
This can be run as:
./runit.sh -it --rm alpine id
or, for a shell (alpine doesn't have bash by default):
./runit.sh -it --rm centos bash --login
You can throw in a -w $HOME to get it to start in the user's home directory, etc.