Not today...

DISCLAIMER: This is now fixed in git new releases and does not need to be done anymore. I use an old version of alpine in order to have an unpached version of git.

I ran into an interesting issue lastly. I wanted to mount a volume inside a container and clone a repo in it. I also wanted to avoid messing with the permissions and pass my user to the container as well.

Set test env

Here is my setup, a Dockerfile with a container and git installed

FROM alpine:3.2
RUN apk --update add git

Then simply run the git clone command inside a volume mounted with correct uid and gid.

docker build -t foo --rm .
docker run --rm -u 1000:1000 -v $(pwd):/mnt -w /mnt test \
	git clone https://github.com/octocat/Spoon-Knife

And I get the following error: fatal: unable to look up current user in the passwd file: no such user. This is actually right, my user only exists on the host and not into my container.

Googling

I checked my best friend for technical questions: Google. And found this thread which describe exactly what I am facing right now. The thread is really interesting and I invite you to read it entirely.

A solution is suggested here. What does it say? Just disable the reflog at clone time. I still have an issue here because I do not have the hand on the cloning command in my real life issue.

Googling again, nothing really obvious came here. So better check at the git documentation, and more precisely at the git config man page. Looking for reflog and ended up here. Great, there is a trigger!

Fixing

We now have to set this option inside the Dockerfile in order to make the process able to clone the repo correctly. There is an option inside the git config we will use: --system described here. This will set the configuration system wide, because the cloning will occur with a random uid, we need a generic setup, whereas --global as root will only set the option for the root user.

Final setup

We modify our Dockerfile according to the last results.

FROM alpine:3.2

RUN apk --update add git
RUN git config --system core.logallrefupdates false

The git config command is case insensitive, so all lowercase will work here. Now just run the previous build and run again your git clone.

It works!