So Image.inside does not work inside withTool if you did not in fact have a docker in your $PATH otherwise.
docker.inside fails to run `docker` on a docker4mac ssh slave
Automatic installer fails for Docker 1.11 and latest
CloudBees Internal CJP-5559
CloudBees Internal OSS-1437
Without the fix for JENKINS-36082 this is a moot point.
sh 'uname -a'
You will see the build fail with the attached log file.
Actually need to pass -v JENKINS-37951-remotefs:/home/jenkins to the agent launch command, and pick /home/jenkins as the remote FS root. Then I find another bug, which I will fix: the --volumes-from detection incorrectly assumed that volumes had been predeclared (VOLUME in Dockerfile). Useful to add another sh 'uname -a' directly inside node to see this.
Code changed in jenkins
User: Jesse Glick
[FIXED JENKINS-37951] Honor withTool from Image.inside.