adamkdean

software engineering

Copying files from one container to another

By Adam K Dean on

This only works on OS X as I'm using pbcopy and pbpaste. You may replace these as you see fit. Also I'm using superdocker here, you can swap that for docker if you like, it makes no difference.

What I needed to do was copy some SSL certificates from one container to another. I wanted the easiest way of doing this for the future. Thus I came up with this somewhat messy solution. I like it though. In this case the source container is called 'registry' and the destination container is a data volume container called 'publisherd-data'.

superdocker exec -ti $(superdocker ps | grep registry | awk '{print $1}') \
    cat /go/src/github.com/docker/distribution/certs/domain.crt | \
    pbcopy && \
    superdocker run --rm -ti \
        --volumes-from publisherd-data \
        ubuntu bash -c "echo '$(pbpaste)' > /etc/nginx/certs/registry.domain.com.crt"

superdocker exec -ti $(superdocker ps | grep registry | awk '{print $1}') \
    cat /go/src/github.com/docker/distribution/certs/domain.key | \
    pbcopy && \
    superdocker run --rm -ti \
        --volumes-from publisherd-data \
        ubuntu bash -c "echo '$(pbpaste)' > /etc/nginx/certs/registry.domain.com.key"

To break it down, we first grab the certificate by running docker exec on the source container, which we find by doing a quick docker ps | grep | awk.

superdocker exec -ti $(superdocker ps | grep registry | awk '{print $1}') \
    cat /go/src/github.com/docker/distribution/certs/domain.crt

Next we pipe that to pbcopy, the OS X clibpoard utility.

superdocker exec -ti $(superdocker ps | grep registry | awk '{print $1}') \
    cat /go/src/github.com/docker/distribution/certs/domain.crt | \
    pbcopy

Then we run an ethereal container which we connect to the destination data volume container. We then simply empty our clipboard into the destination file.

superdocker exec -ti $(superdocker ps | grep registry | awk '{print $1}') \
    cat /go/src/github.com/docker/distribution/certs/domain.crt | \
    pbcopy && \
    superdocker run --rm -ti \
        --volumes-from publisherd-data \
        ubuntu bash -c "echo '$(pbpaste)' > /etc/nginx/certs/registry.domain.com.crt"

It's a figurative mouthful, but it does the trick without saving your certs anywhere. You might also want to clear that clipboard afterwards though.

echo '' | pbcopy