Copy build artifacts from insider docker to host - docker

Question

This is my jenkinsfile:
pipeline {
agent any
stages {
stage('Build') {
steps {
echo '####################################################
echo 'Building Docker container'
echo '####################################################
script {
sh 'docker build -t my-gcc:1.0 .'
}
}
}
stage('Run') {
steps {
echo '##########################################################
echo 'Running Docker Image'
echo '##########################################################
script {
sh 'docker run --privileged -i my-gcc:1.0'
sh 'docker cp my-gcc:1.0:/usr/src/myCppProject/build/*.hex .'
}
}
}
stage('Program') {
steps {
echo '#######################################################
echo 'Programming target '
echo '#######################################################
script {
sh 'openocd -d0 -f board/st_nucleo_f4.cfg -c "init;targets;halt;flash write_image erase Testbench.hex;shutdown"'
}
}
}
}
}
the docker image is build and then run, after this I would like to extract the hex file form the container to the jenkins working directory so that I can flash it to the board.
But when I try to copy the file I get this error:
+ docker cp my-gcc:1.0:1.0:/usr/src/myCppProject/build/*.hex .
Error: No such container:path: my-gcc:1.0:1.0:/usr/src/myCppProject/build/*.hex
I tried to access other folders in the container and copy the content, but always the same error. This way it seems that I cannot access any folder or file in the container.
What am I doing wrong?
Regards
Martin

Answer 1

Jenkins has some standard support for Docker; this is described in Using Docker with Pipeline in the Jenkins documentation. In particular, Jenkins knows how to use a Docker image that contains just tools, combined with the project's workspace directory. I'd use that support instead of trying to script docker cp.
That might look roughly like so:
pipeline {
agent none
stages {
stage('Build') {
// Jenkins will run `docker build` for you
agent { dockerfile { args '--privileged' } }
steps {
// The current working directory is bind-mounted into the container;
// the image's `ENTRYPOINT`/`CMD` is ignored.
// Copy the file out of the container:
sh "cp /usr/src/myCppProject/build/*.hex ."
}
}
stage('Program') {
agent any // so not in Docker
steps {
sh 'openocd -d0 -f board/st_nucleo_f4.cfg -c "init;targets;halt;flash write_image erase Testbench.hex;shutdown"'
}
}
}
}
If you use this approach, also consider whether you should run the main build sequence via Jenkins pipeline steps, or a sh invocation that runs a shell script, or a Makefile, or if a Dockerfile is actually right. It might make sense to build a Docker image out of your customized compiler, but then use the Jenkins pipeline support to build the image for the target board rather than trying to do it all in a Dockerfile.
In the invocation you show, you can't directly docker cp a file out of an image. When you start the container, use docker run --name to give it a name, then docker cp from that container name.
sh 'docker run --name builder ... my-gcc:1.0'
sh 'docker cp builder:/usr/src/myCppProject/build/*.hex .'
sh 'docker rm builder'