Issue docker commands on Jenkins slave

Question

I have a Jenkins master running on Windows Server 2016. I need to be able to run linux containers to run some automated e2e tests. For reasons I won't get into, I cannot enable hyper-v on this machine. This is preventing me from installing lcow and docker on my Jenkins master

What I've done instead is setup a Ubuntu 18.04 VM in virtualbox and installed docker there. I've configured the VM as a Jenkins slave using ssh to login as the jenkins user. I've setup and configured everything for this user to be able to run docker commands without using sudo. If I manually ssh into the server as the jenkins user I can run docker commands without an issue. Everything works the way you would expect.

I've then setup a test build to check that everything was working correctly. The problem is that when I try to run docker commands using the Execute Shell build step I'm getting a docker: not found error. From what I can tell, the build is running as the correct user. I added who -u to the build step so I could check which user the build was running as.

Here is the output from my build:

[TEST - e2e - TEST] $ /bin/sh -xe /tmp/jenkins16952572249375249520.sh
+ who -u
jenkins  pts/0        2018-08-10 16:43   .         10072 (10.0.2.2)
+ docker run hello-world
/tmp/jenkins16952572249375249520.sh: 3: /tmp/jenkins16952572249375249520.sh: docker: not found

As I mentioned, the jenkins user has been added to the docker group and Docker has been added to $PATH (/snap/bin/):

jenkins@jenkins-docker-slave:~$ which docker
/snap/bin/docker
jenkins@jenkins-docker-slave:~$ $PATH
-bash:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin: No such file or directory
jenkins@jenkins-docker-slave:~$ who -u
jenkins  pts/0        2018-08-10 16:43   .         10072 (10.0.2.2)
jenkins@jenkins-docker-slave:~$ cat /etc/group | grep docker
docker:x:1001:qctesting,jenkins

As you can see by this snippet I can successfully run docker commands by logging into the server as the jenkins user:

jenkins@jenkins-docker-slave:~$ docker run hello-world

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
(amd64)
 3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/engine/userguide/

I have also configured the path to docker in the slaves node properties as I thought it would fix my issue. As you can see I have both git and docker listed. Git commands are working just fine. It is only the docker commands that are giving me problems. I have tried both /snap/bin and /snap/bin/docker with no luck.

I am trying to build a jenkins job that will clone a git repo, spin up the containers I need using docker-compose and some build parameters I pass in at build time, and run my e2e tests against any environment (qa, staging, production, etc.). I just can't get the jenkins slave to run the docker commands. What am I missing? How can I get the slave to recognize that docker is already installed on the system and the user has the correct permissions to execute those commands.

NOTE: I am NOT trying to run docker in docker. Practically all questions/documentation I've found on running docker commands on a jenkins slave describe how to solve this issue by running the slave in a docker container and installing the docker client in the slave container. That is not what I'm trying to accomplish. I am trying to ssh from a jenkins master into a jenkins slave that already has docker installed and run docker commands on that server as the jenkins user.

Answer 1

I finally figured this out thanks to the answer for this question. After reading that answer I realized I had installed the wrong version of docker on Ubuntu. I removed the previous installation and installed the correct docker package using sudo curl -sSL https://get.docker.com/ | sh. I then restarted my jenkins slave and everything started working.