coreos-docker-setup

These are the steps I took to setup a coreos installation to host various docker containers

1. Create vm with at least 2GB of ram (required?) and boot from coreos iso
2. openssl passwd -1 > cloud-config.yml
3. vim cloud-config.yml and add the following lines

    #cloud-config
      users:
        - name: coreuser
          passwd: $1$QJq0Z7rL$GjaetUaSVEU0hM5N3VKpn.
          groups:
            - sudo
            - docker
            
4. coreos-cloudinit -validate --from-file cloud-config.yml
5. coreos-install -d /dev/sda -C stable -c cloud-config.yml
6. after installation completes remove iso and reboot

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This is how I setup docker-compose on coreos

1. vim /var/lib/coreos-install/user_data (this is the location of the cloud-config file we created https://coreos.com/os/docs/latest/cloud-config-locations.html)
2. Add the following lines

    coreos:
      units:
        - name: install-docker-compose.service
          command: start
          content: |
            [Unit]
            Description=Install docker-compose
            ConditionPathExists=!/opt/bin/docker-compose

            [Service]
            Type=oneshot
            RemainAfterExit=yes
            ExecStart=/usr/bin/mkdir -p /opt/bin/
            ExecStart=/usr/bin/curl -o /opt/bin/docker-compose -sL "https://github.com/docker/compose/releases/download/1.21.2/docker-compose-Linux-x86_64"
            ExecStart=/usr/bin/chmod +x /opt/bin/docker-compose
            
3. coreos-cloudinit -validate --from-file /var/lib/coreos-install/user_data
4. coreos-cloudinit --from-file /var/lib/coreos-install/user_data

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This is how I setup a cifs mount for shared data storage

1. added following to /var/lib/coreos-install/user_data

  units:
    - name: basic-mount-cifs.service
      enable: true
      content: |
        [Unit]
        Description=Download basic mount.cifs binary
        Documentation=https://github.com/xynova/docker-cifs-build
        After=network.target
        ConditionFileIsExecutable=!/opt/bin/mount.cifs

        [Service]
        TimeoutStartSec=0
        Environment="WORKDIR=/tmp/cifs-mount"
        Environment="BINDIR=/opt/bin"
        Environment="PKGADDR=quay.io/xynova/cifs-mount"
        ExecStartPre=/usr/bin/mkdir -p $BINDIR $WORKDIR
        #Download container
        ExecStartPre=/bin/curl -o ${WORKDIR}/pkg -L https://xynova+reader:SFZ78VTCO2TNUL6NHTBAWZBU68U1LPCT7EQ26B1ID6MIP3FZOFYRLXSF331WEQT4@quay.io/c1/squash/xynova/cifs-mount/latest
        # Manually extract mount.cifs from container into /opt/bin
        ExecStartPre=/bin/bash -c "cd $WORKDIR && tar -ztf pkg | grep .tar \
        | xargs tar -zxvf pkg $1 \
        | xargs tar -xv sbin/mount.cifs -f $1"
        ExecStart=/bin/bash -c "cp ${WORKDIR}/sbin/mount.cifs ${BINDIR}/ && rm -Rf $WORKDIR"

        [Install]
        WantedBy=multi-user.target
        RequiredBy=docker.service
    - name: mount-cifs-share.service
      enable: true
      content: |
        [Unit]
        Description=Mount a cifs share
        Requires=basic-mount-cifs.service
        After=basic-mount-cifs.service
        ConditionPathExists=/opt/bin/mount.cifs

        [Service]
        Type=oneshot
        RemainAfterExit=yes
        TimeoutStartSec=0
        ExecStartPre=/usr/bin/mkdir -p /srv/datalink
        ExecStart=/opt/bin/mount.cifs -o vers=2.1,username=guest,password=,uid=1000,gid=1000 //server.path.com/share/path /srv/datalink/
        
        [Install]
        WantedBy=multi-user.target
        RequiredBy=docker.service
        
2. coreos-cloudinit -validate --from-file /var/lib/coreos-install/user_data
3. coreos-cloudinit --from-file /var/lib/coreos-install/user_data
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Good links

https://stackoverflow.com/questions/29086918/docker-compose-to-coreos

https://www.digitalocean.com/community/tutorials/understanding-systemd-units-and-unit-files

https://coreos.com/os/docs/latest/getting-started-with-docker.html

https://docs.docker.com/engine/faq