title: Ubuntu - install (Jenkins) Docker containers fails due to creating mount source path: mkdir read-only errors
body: <p>I want to install Jenkins via Docker in an Ubuntu virtual machine (Oracle VM Virtualbox). </p>
  
  <p>When starting 'docker-compose up' I get the following errors: </p>
  
  <blockquote>
    <p>ERROR: for dockercompose_postgres_1  Cannot start service postgres:
    error while creating mount source path '/var/postgres-data': mkdir
    /var/postgres-data: read-Starting dockercompose_jenkins_1 ... error</p>
    
    <p>ERROR: for dockercompose_jenkins_1  Cannot start service jenkins:
    error while creating mount source path '/var/jenkins_home': mkdir
    /var/jenkins_home: read-only file system</p>
    
    <p>ERROR: for jenkins  Cannot start service jenkins: error while creating
    mount source path '/var/jenkins_home': mkdir /var/jenkins_home:
    read-only file system</p>
    
    <p>ERROR: for postgres  Cannot start service postgres: error while
    creating mount source path '/var/postgres-data': mkdir
    /var/postgres-data: read-only file system ERROR: Encountered errors
    while bringing up the project.</p>
  </blockquote>
  
  <p>The context: </p>
  
  <ul>
  <li>I am logged in as 'osboxes.org' (same name as the Ubuntu image provider). </li>
  <li>Docker-compose is started as 'sudo docker-compose up'. </li>
  <li>The permissions of the folder '/var' is drwxrwxrwx  14 root root  4096 Sep  9 08:48 var</li>
  <li>At first the /var/progres-data and /var/jenkins_home are not existing. The issue is there. </li>
  <li>After creating both folders / directories with 777 permission, the same issue is there. </li>
  <li>The Ubuntu VM is an Osboxes.org Ubuntu virtual machine in Oracle VM Virtualbox on Windows. </li>
  <li>Suggested was a 'sudo mount -o remount,rw /'. No changes. </li>
  <li>Suggested was a 'sudo mount -o remount,rw /var', then I get this warning: mount: /var: mount point not mounted or bad option.</li>
  </ul>
  
  <p>Part of the docker-compose.yml file is: </p>
  
  <pre><code>version: '2'
    services:   jenkins:
      image: jenkins:latest
      ports:
        - "8080:8080"
        - "50000:50000"
      networks:
        - jenkins
      volumes:
        - /var/jenkins_home:/var/jenkins_home
        - /var/run/docker.sock:/var/run/docker.sock   
    postgres:
      image: postgres:9.6
      networks:
        - jenkins
      environment:
        POSTGRES_USER: sonar
        POSTGRES_PASSWORD: sonarpasswd
      volumes:
        - /var/postgres-data:/var/lib/postgresql/data
        ETC ETC ETC
  </code></pre>