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Deploy a CoreOS running Kubernetes environment. This particular guide is made to help those in an OFFLINE system, wither for testing a POC before the real deal, or you are restricted to be totally offline for your applications.

Prerequisites

  1. Installed CentOS 6 for PXE server
  2. At least two bare metal nodes to work with

High Level Design

  1. Manage the tftp directory
    • /tftpboot/(coreos)(centos)(RHEL)
    • /tftpboot/pxelinux.0/(MAC) -> linked to Linux image config file
  2. Update per install the link for pxelinux
  3. Update the DHCP config to reflect the host needing deployment
  4. Setup nodes to deploy CoreOS creating an etcd cluster.
  5. Have no access to the public etcd discovery tool.
  6. Installing the CoreOS slaves to become Kubernetes nodes.

This Guides variables

Node Description MAC IP
CoreOS/etcd/Kubernetes Master d0:00:67:13:0d:00 10.20.30.40
CoreOS Slave 1 d0:00:67:13:0d:01 10.20.30.41
CoreOS Slave 2 d0:00:67:13:0d:02 10.20.30.42

Setup PXELINUX CentOS

To setup CentOS PXELINUX environment there is a complete guide here. This section is the abbreviated version.

  1. Install packages needed on CentOS
sudo yum install tftp-server dhcp syslinux
  1. vi /etc/xinetd.d/tftp to enable tftp service and change disable to ‘no’
disable = no
  1. Copy over the syslinux images we will need.
su -
mkdir -p /tftpboot
cd /tftpboot
cp /usr/share/syslinux/pxelinux.0 /tftpboot
cp /usr/share/syslinux/menu.c32 /tftpboot
cp /usr/share/syslinux/memdisk /tftpboot
cp /usr/share/syslinux/mboot.c32 /tftpboot
cp /usr/share/syslinux/chain.c32 /tftpboot

/sbin/service dhcpd start
/sbin/service xinetd start
/sbin/chkconfig tftp on
  1. Setup default boot menu
mkdir /tftpboot/pxelinux.cfg
touch /tftpboot/pxelinux.cfg/default
  1. Edit the menu vi /tftpboot/pxelinux.cfg/default
default menu.c32
prompt 0
timeout 15
ONTIMEOUT local
display boot.msg

MENU TITLE Main Menu

LABEL local
        MENU LABEL Boot local hard drive
        LOCALBOOT 0

Now you should have a working PXELINUX setup to image CoreOS nodes. You can verify the services by using VirtualBox locally or with bare metal servers.

Adding CoreOS to PXE

This section describes how to setup the CoreOS images to live alongside a pre-existing PXELINUX environment.

  1. Find or create the TFTP root directory that everything will be based on.
    • For this document we will assume /tftpboot/ is our root directory.
  2. Once we know and have our tftp root directory we will create a new directory structure for our CoreOS images.
  3. Download the CoreOS PXE files provided by the CoreOS team.
MY_TFTPROOT_DIR=/tftpboot
mkdir -p $MY_TFTPROOT_DIR/images/coreos/
cd $MY_TFTPROOT_DIR/images/coreos/
wget http://stable.release.core-os.net/amd64-usr/current/coreos_production_pxe.vmlinuz
wget http://stable.release.core-os.net/amd64-usr/current/coreos_production_pxe.vmlinuz.sig
wget http://stable.release.core-os.net/amd64-usr/current/coreos_production_pxe_image.cpio.gz
wget http://stable.release.core-os.net/amd64-usr/current/coreos_production_pxe_image.cpio.gz.sig
gpg --verify coreos_production_pxe.vmlinuz.sig
gpg --verify coreos_production_pxe_image.cpio.gz.sig
  1. Edit the menu vi /tftpboot/pxelinux.cfg/default again
default menu.c32
prompt 0
timeout 300
ONTIMEOUT local
display boot.msg

MENU TITLE Main Menu

LABEL local
        MENU LABEL Boot local hard drive
        LOCALBOOT 0

MENU BEGIN CoreOS Menu

    LABEL coreos-master
        MENU LABEL CoreOS Master
        KERNEL images/coreos/coreos_production_pxe.vmlinuz
        APPEND initrd=images/coreos/coreos_production_pxe_image.cpio.gz cloud-config-url=http://<xxx.xxx.xxx.xxx>/pxe-cloud-config-single-master.yml

    LABEL coreos-slave
        MENU LABEL CoreOS Slave
        KERNEL images/coreos/coreos_production_pxe.vmlinuz
        APPEND initrd=images/coreos/coreos_production_pxe_image.cpio.gz cloud-config-url=http://<xxx.xxx.xxx.xxx>/pxe-cloud-config-slave.yml
MENU END

This configuration file will now boot from local drive but have the option to PXE image CoreOS.

DHCP configuration

This section covers configuring the DHCP server to hand out our new images. In this case we are assuming that there are other servers that will boot alongside other images.

  1. Add the filename to the host or subnet sections.
filename "/tftpboot/pxelinux.0";
  1. At this point we want to make pxelinux configuration files that will be the templates for the different CoreOS deployments.
subnet 10.20.30.0 netmask 255.255.255.0 {
        next-server 10.20.30.242;
        option broadcast-address 10.20.30.255;
        filename "<other default image>";

        ...
        # http://www.syslinux.org/wiki/index.php/PXELINUX
        host core_os_master {
                hardware ethernet d0:00:67:13:0d:00;
                option routers 10.20.30.1;
                fixed-address 10.20.30.40;
                option domain-name-servers 10.20.30.242;
                filename "/pxelinux.0";
        }
        host core_os_slave {
                hardware ethernet d0:00:67:13:0d:01;
                option routers 10.20.30.1;
                fixed-address 10.20.30.41;
                option domain-name-servers 10.20.30.242;
                filename "/pxelinux.0";
        }
        host core_os_slave2 {
                hardware ethernet d0:00:67:13:0d:02;
                option routers 10.20.30.1;
                fixed-address 10.20.30.42;
                option domain-name-servers 10.20.30.242;
                filename "/pxelinux.0";
        }
        ...
}

We will be specifying the node configuration later in the guide.

Kubernetes

To deploy our configuration we need to create an etcd master. To do so we want to pxe CoreOS with a specific cloud-config.yml. There are two options we have here. 1. Is to template the cloud config file and programmatically create new static configs for different cluster setups. 2. Have a service discovery protocol running in our stack to do auto discovery.

This demo we just make a static single etcd server to host our Kubernetes and etcd master servers.

Since we are OFFLINE here most of the helping processes in CoreOS and Kubernetes are then limited. To do our setup we will then have to download and serve up our binaries for Kubernetes in our local environment.

An easy solution is to host a small web server on the DHCP/TFTP host for all our binaries to make them available to the local CoreOS PXE machines.

To get this up and running we are going to setup a simple apache server to serve our binaries needed to bootstrap Kubernetes.

This is on the PXE server from the previous section:

rm /etc/httpd/conf.d/welcome.conf
cd /var/www/html/
wget -O kube-register  https://github.com/kelseyhightower/kube-register/releases/download/v0.0.2/kube-register-0.0.2-linux-amd64
wget -O setup-network-environment https://github.com/kelseyhightower/setup-network-environment/releases/download/v1.0.0/setup-network-environment
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kubernetes --no-check-certificate
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kube-apiserver --no-check-certificate
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kube-controller-manager --no-check-certificate
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kube-scheduler --no-check-certificate
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kubectl --no-check-certificate
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kubecfg --no-check-certificate
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kubelet --no-check-certificate
wget https://storage.googleapis.com/kubernetes-release/release/v0.15.0/bin/linux/amd64/kube-proxy --no-check-certificate
wget -O flanneld https://storage.googleapis.com/k8s/flanneld --no-check-certificate

This sets up our binaries we need to run Kubernetes. This would need to be enhanced to download from the Internet for updates in the future.

Now for the good stuff!

Cloud Configs

The following config files are tailored for the OFFLINE version of a Kubernetes deployment.

These are based on the work found here: master.yml, node.yml

To make the setup work, you need to replace a few placeholders:

master.yml

On the PXE server make and fill in the variables vi /var/www/html/coreos/pxe-cloud-config-master.yml.

#cloud-config
---
write_files:
  - path: /opt/bin/waiter.sh
    owner: root
    content: |
      #! /usr/bin/bash
      until curl http://127.0.0.1:4001/v2/machines; do sleep 2; done
  - path: /opt/bin/kubernetes-download.sh
    owner: root
    permissions: 0755
    content: |
      #! /usr/bin/bash
      /usr/bin/wget -N -P "/opt/bin" "http://<PXE_SERVER_IP>/kubectl"
      /usr/bin/wget -N -P "/opt/bin" "http://<PXE_SERVER_IP>/kubernetes"
      /usr/bin/wget -N -P "/opt/bin" "http://<PXE_SERVER_IP>/kubecfg"
      chmod +x /opt/bin/*
  - path: /etc/profile.d/opt-path.sh
    owner: root
    permissions: 0755
    content: |
      #! /usr/bin/bash
      PATH=$PATH/opt/bin
coreos:
  units:
    - name: 10-eno1.network
      runtime: true
      content: |
        [Match]
        Name=eno1
        [Network]
        DHCP=yes
    - name: 20-nodhcp.network
      runtime: true
      content: |
        [Match]
        Name=en*
        [Network]
        DHCP=none
    - name: get-kube-tools.service
      runtime: true
      command: start
      content: |
        [Service]
        ExecStartPre=-/usr/bin/mkdir -p /opt/bin
        ExecStart=/opt/bin/kubernetes-download.sh
        RemainAfterExit=yes
        Type=oneshot
    - name: setup-network-environment.service
      command: start
      content: |
        [Unit]
        Description=Setup Network Environment
        Documentation=https://github.com/kelseyhightower/setup-network-environment
        Requires=network-online.target
        After=network-online.target
        [Service]
        ExecStartPre=-/usr/bin/mkdir -p /opt/bin
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/setup-network-environment
        ExecStartPre=/usr/bin/chmod +x /opt/bin/setup-network-environment
        ExecStart=/opt/bin/setup-network-environment
        RemainAfterExit=yes
        Type=oneshot
    - name: etcd.service
      command: start
      content: |
        [Unit]
        Description=etcd
        Requires=setup-network-environment.service
        After=setup-network-environment.service
        [Service]
        EnvironmentFile=/etc/network-environment
        User=etcd
        PermissionsStartOnly=true
        ExecStart=/usr/bin/etcd \
        --name ${DEFAULT_IPV4} \
        --addr ${DEFAULT_IPV4}:4001 \
        --bind-addr 0.0.0.0 \
        --cluster-active-size 1 \
        --data-dir /var/lib/etcd \
        --http-read-timeout 86400 \
        --peer-addr ${DEFAULT_IPV4}:7001 \
        --snapshot true
        Restart=always
        RestartSec=10s
    - name: fleet.socket
      command: start
      content: |
        [Socket]
        ListenStream=/var/run/fleet.sock
    - name: fleet.service
      command: start
      content: |
        [Unit]
        Description=fleet daemon
        Wants=etcd.service
        After=etcd.service
        Wants=fleet.socket
        After=fleet.socket
        [Service]
        Environment="FLEET_ETCD_SERVERS=http://127.0.0.1:4001"
        Environment="FLEET_METADATA=role=master"
        ExecStart=/usr/bin/fleetd
        Restart=always
        RestartSec=10s
    - name: etcd-waiter.service
      command: start
      content: |
        [Unit]
        Description=etcd waiter
        Wants=network-online.target
        Wants=etcd.service
        After=etcd.service
        After=network-online.target
        Before=flannel.service
        Before=setup-network-environment.service
        [Service]
        ExecStartPre=/usr/bin/chmod +x /opt/bin/waiter.sh
        ExecStart=/usr/bin/bash /opt/bin/waiter.sh
        RemainAfterExit=true
        Type=oneshot
    - name: flannel.service
      command: start
      content: |
        [Unit]
        Wants=etcd-waiter.service
        After=etcd-waiter.service
        Requires=etcd.service
        After=etcd.service
        After=network-online.target
        Wants=network-online.target
        Description=flannel is an etcd backed overlay network for containers
        [Service]
        Type=notify
        ExecStartPre=-/usr/bin/mkdir -p /opt/bin
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/flanneld
        ExecStartPre=/usr/bin/chmod +x /opt/bin/flanneld
        ExecStartPre=-/usr/bin/etcdctl mk /coreos.com/network/config '{"Network":"10.100.0.0/16", "Backend": {"Type": "vxlan"}}'
        ExecStart=/opt/bin/flanneld
    - name: kube-apiserver.service
      command: start
      content: |
        [Unit]
        Description=Kubernetes API Server
        Documentation=https://github.com/kubernetes/kubernetes
        Requires=etcd.service
        After=etcd.service
        [Service]
        ExecStartPre=-/usr/bin/mkdir -p /opt/bin
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/kube-apiserver
        ExecStartPre=/usr/bin/chmod +x /opt/bin/kube-apiserver
        ExecStart=/opt/bin/kube-apiserver \
        --address=0.0.0.0 \
        --port=8080 \
        --service-cluster-ip-range=10.100.0.0/16 \
        --etcd-servers=http://127.0.0.1:4001 \
        --logtostderr=true
        Restart=always
        RestartSec=10
    - name: kube-controller-manager.service
      command: start
      content: |
        [Unit]
        Description=Kubernetes Controller Manager
        Documentation=https://github.com/kubernetes/kubernetes
        Requires=kube-apiserver.service
        After=kube-apiserver.service
        [Service]
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/kube-controller-manager
        ExecStartPre=/usr/bin/chmod +x /opt/bin/kube-controller-manager
        ExecStart=/opt/bin/kube-controller-manager \
        --master=127.0.0.1:8080 \
        --logtostderr=true
        Restart=always
        RestartSec=10
    - name: kube-scheduler.service
      command: start
      content: |
        [Unit]
        Description=Kubernetes Scheduler
        Documentation=https://github.com/kubernetes/kubernetes
        Requires=kube-apiserver.service
        After=kube-apiserver.service
        [Service]
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/kube-scheduler
        ExecStartPre=/usr/bin/chmod +x /opt/bin/kube-scheduler
        ExecStart=/opt/bin/kube-scheduler --master=127.0.0.1:8080
        Restart=always
        RestartSec=10
    - name: kube-register.service
      command: start
      content: |
        [Unit]
        Description=Kubernetes Registration Service
        Documentation=https://github.com/kelseyhightower/kube-register
        Requires=kube-apiserver.service
        After=kube-apiserver.service
        Requires=fleet.service
        After=fleet.service
        [Service]
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/kube-register
        ExecStartPre=/usr/bin/chmod +x /opt/bin/kube-register
        ExecStart=/opt/bin/kube-register \
        --metadata=role=node \
        --fleet-endpoint=unix:///var/run/fleet.sock \
        --healthz-port=10248 \
        --api-endpoint=http://127.0.0.1:8080
        Restart=always
        RestartSec=10
  update:
    group: stable
    reboot-strategy: off
ssh_authorized_keys:
  - ssh-rsa AAAAB3NzaC1yc2EAAAAD...

node.yml

On the PXE server make and fill in the variables vi /var/www/html/coreos/pxe-cloud-config-slave.yml.

#cloud-config
---
write_files:
  - path: /etc/default/docker
    content: |
      DOCKER_EXTRA_OPTS='--insecure-registry="rdocker.example.com:5000"'
coreos:
  units:
    - name: 10-eno1.network
      runtime: true
      content: |
        [Match]
        Name=eno1
        [Network]
        DHCP=yes
    - name: 20-nodhcp.network
      runtime: true
      content: |
        [Match]
        Name=en*
        [Network]
        DHCP=none
    - name: etcd.service
      mask: true
    - name: docker.service
      drop-ins:
        - name: 50-insecure-registry.conf
          content: |
            [Service]
            Environment="HTTP_PROXY=http://rproxy.example.com:3128/" "NO_PROXY=localhost,127.0.0.0/8,rdocker.example.com"
    - name: fleet.service
      command: start
      content: |
        [Unit]
        Description=fleet daemon
        Wants=fleet.socket
        After=fleet.socket
        [Service]
        Environment="FLEET_ETCD_SERVERS=http://<MASTER_SERVER_IP>:4001"
        Environment="FLEET_METADATA=role=node"
        ExecStart=/usr/bin/fleetd
        Restart=always
        RestartSec=10s
    - name: flannel.service
      command: start
      content: |
        [Unit]
        After=network-online.target
        Wants=network-online.target
        Description=flannel is an etcd backed overlay network for containers
        [Service]
        Type=notify
        ExecStartPre=-/usr/bin/mkdir -p /opt/bin
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/flanneld
        ExecStartPre=/usr/bin/chmod +x /opt/bin/flanneld
        ExecStart=/opt/bin/flanneld -etcd-endpoints http://<MASTER_SERVER_IP>:4001
    - name: docker.service
      command: start
      content: |
        [Unit]
        After=flannel.service
        Wants=flannel.service
        Description=Docker Application Container Engine
        Documentation=http://docs.docker.io
        [Service]
        EnvironmentFile=-/etc/default/docker
        EnvironmentFile=/run/flannel/subnet.env
        ExecStartPre=/bin/mount --make-rprivate /
        ExecStart=/usr/bin/docker -d --bip=${FLANNEL_SUBNET} --mtu=${FLANNEL_MTU} -s=overlay -H fd:// ${DOCKER_EXTRA_OPTS}
        [Install]
        WantedBy=multi-user.target
    - name: setup-network-environment.service
      command: start
      content: |
        [Unit]
        Description=Setup Network Environment
        Documentation=https://github.com/kelseyhightower/setup-network-environment
        Requires=network-online.target
        After=network-online.target
        [Service]
        ExecStartPre=-/usr/bin/mkdir -p /opt/bin
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/setup-network-environment
        ExecStartPre=/usr/bin/chmod +x /opt/bin/setup-network-environment
        ExecStart=/opt/bin/setup-network-environment
        RemainAfterExit=yes
        Type=oneshot
    - name: kube-proxy.service
      command: start
      content: |
        [Unit]
        Description=Kubernetes Proxy
        Documentation=https://github.com/kubernetes/kubernetes
        Requires=setup-network-environment.service
        After=setup-network-environment.service
        [Service]
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/kube-proxy
        ExecStartPre=/usr/bin/chmod +x /opt/bin/kube-proxy
        ExecStart=/opt/bin/kube-proxy \
        --etcd-servers=http://<MASTER_SERVER_IP>:4001 \
        --logtostderr=true
        Restart=always
        RestartSec=10
    - name: kube-kubelet.service
      command: start
      content: |
        [Unit]
        Description=Kubernetes Kubelet
        Documentation=https://github.com/kubernetes/kubernetes
        Requires=setup-network-environment.service
        After=setup-network-environment.service
        [Service]
        EnvironmentFile=/etc/network-environment
        ExecStartPre=/usr/bin/wget -N -P /opt/bin http://<PXE_SERVER_IP>/kubelet
        ExecStartPre=/usr/bin/chmod +x /opt/bin/kubelet
        ExecStart=/opt/bin/kubelet \
        --address=0.0.0.0 \
        --port=10250 \
        --hostname-override=${DEFAULT_IPV4} \
        --api-servers=<MASTER_SERVER_IP>:8080 \
        --healthz-bind-address=0.0.0.0 \
        --healthz-port=10248 \
        --logtostderr=true
        Restart=always
        RestartSec=10
  update:
    group: stable
    reboot-strategy: off
ssh_authorized_keys:
  - ssh-rsa AAAAB3NzaC1yc2EAAAAD...

New pxelinux.cfg file

Create a pxelinux target file for a slave node: vi /tftpboot/pxelinux.cfg/coreos-node-slave

default coreos
prompt 1
timeout 15

display boot.msg

label coreos
    menu default
    kernel images/coreos/coreos_production_pxe.vmlinuz
    append initrd=images/coreos/coreos_production_pxe_image.cpio.gz cloud-config-url=http://<pxe-host-ip>/coreos/pxe-cloud-config-slave.yml console=tty0 console=ttyS0 coreos.autologin=tty1 coreos.autologin=ttyS0

And one for the master node: vi /tftpboot/pxelinux.cfg/coreos-node-master

default coreos
prompt 1
timeout 15

display boot.msg

label coreos
    menu default
    kernel images/coreos/coreos_production_pxe.vmlinuz
    append initrd=images/coreos/coreos_production_pxe_image.cpio.gz cloud-config-url=http://<pxe-host-ip>/coreos/pxe-cloud-config-master.yml console=tty0 console=ttyS0 coreos.autologin=tty1 coreos.autologin=ttyS0

Specify the pxelinux targets

Now that we have our new targets setup for master and slave we want to configure the specific hosts to those targets. We will do this by using the pxelinux mechanism of setting a specific MAC addresses to a specific pxelinux.cfg file.

Refer to the MAC address table in the beginning of this guide. Documentation for more details can be found here.

cd /tftpboot/pxelinux.cfg
ln -s coreos-node-master 01-d0-00-67-13-0d-00
ln -s coreos-node-slave 01-d0-00-67-13-0d-01
ln -s coreos-node-slave 01-d0-00-67-13-0d-02

Reboot these servers to get the images PXEd and ready for running containers!

Creating test pod

Now that the CoreOS with Kubernetes installed is up and running lets spin up some Kubernetes pods to demonstrate the system.

See a simple nginx example to try out your new cluster.

For more complete applications, please look in the examples directory.

Helping commands for debugging

List all keys in etcd:

etcdctl ls --recursive

List fleet machines

fleetctl list-machines

Check system status of services on master:

systemctl status kube-apiserver
systemctl status kube-controller-manager
systemctl status kube-scheduler
systemctl status kube-register

Check system status of services on a node:

systemctl status kube-kubelet
systemctl status docker.service

List Kubernetes

kubectl get pods
kubectl get nodes

Kill all pods:

for i in `kubectl get pods | awk '{print $1}'`; do kubectl delete pod $i; done

Support Level

IaaS Provider Config. Mgmt OS Networking Docs Conforms Support Level
Bare-metal (Offline) CoreOS CoreOS flannel docs   Community (@jeffbean)

For support level information on all solutions, see the Table of solutions chart.

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