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Host Preparation

Setting PATH

The PATH for the root user on each host must contain the following directories:

  • /bin

  • /sbin

  • /usr/bin

  • /usr/sbin

These should all be included by default in a fresh RHEL 7.x installation.

Operating System Requirements

A base installation of RHEL 7.3 (with the latest packages from the Extras channel) or RHEL Atomic Host 7.3.2 or later is required for master and node hosts. RHEL 7.2 is also supported using Docker 1.12 and its dependencies. See the following documentation for the respective installation instructions, if required:

Host Registration

Each host must be registered using Red Hat Subscription Manager (RHSM) and have an active OpenShift Container Platform subscription attached to access the required packages.

  1. On each host, register with RHSM:

    # subscription-manager register --username=<user_name> --password=<password>

  2. List the available subscriptions:

    # subscription-manager list --available --matches '*OpenShift*'

  3. In the output for the previous command, find the pool ID for an OpenShift Container Platform subscription and attach it:

    # subscription-manager attach --pool=<pool_id>

  4. Disable all yum repositories:

    1. Disable all the enabled RHSM repositories:

      # subscription-manager repos --disable="*"

    2. List the remaining yum repositories and note their names under repo id, if any:

      # yum repolist

    3. Use yum-config-manager to disable the remaining yum repositories:

      # yum-config-manager --disable <repo_id>

      Alternatively, disable all repositories:

       yum-config-manager --disable \*

      Note that this could take a few minutes if you have a large number of available repositories

  5. Enable only the repositories required by OpenShift Container Platform 3.5:

    # subscription-manager repos \
    --enable="rhel-7-server-rpms" \
    --enable="rhel-7-server-extras-rpms" \
    --enable="rhel-7-server-ose-3.5-rpms" \
    --enable="rhel-7-fast-datapath-rpms"

Installing Base Packages

For RHEL 7 systems:

  1. Install the following base packages:

    # yum install wget git net-tools bind-utils yum-utils iptables-services bridge-utils bash-completion kexec-tools sos psacct

  2. Update the system to the latest packages:

    # yum update

  3. Install the following package, which provides OpenShift Container Platform utilities and pulls in other tools required by the quick and advanced installation methods, such as Ansible and related configuration files:

    # yum install atomic-openshift-utils

  4. Install the following *-excluder packages on each RHEL 7 system, which helps ensure your systems stay on the correct versions of atomic-openshift and docker packages when you are not trying to upgrade, according to the OpenShift Container Platform version:

    # yum install atomic-openshift-excluder atomic-openshift-docker-excluder

  5. The *-excluder packages add entries to the exclude directive in the host’s /etc/yum.conf file when installed. Run the following command on each host to remove the atomic-openshift packages from the list for the duration of the installation.

    # atomic-openshift-excluder unexclude

For RHEL Atomic Host 7 systems:

  1. Ensure the host is up to date by upgrading to the latest Atomic tree if one is available:

    # atomic host upgrade

  2. After the upgrade is completed and prepared for the next boot, reboot the host:

    # systemctl reboot

Installing Docker

At this point, you should install Docker on all master and node hosts. This allows you to configure your Docker storage options before installing OpenShift Container Platform.

For RHEL 7 systems, install Docker 1.12:

On RHEL Atomic Host 7 systems, Docker should already be installed, configured, and running by default.

The atomic-openshift-docker-excluder package that was installed in Installing Base Packages should ensure that the correct version of Docker is installed in this step:

# yum install docker

After the package installation is complete, verify that version 1.12 was installed:

# docker version

The Advanced Installation method automatically changes /etc/sysconfig/docker.

The --insecure-registry option instructs the Docker daemon to trust any Docker registry on the indicated subnet, rather than requiring a certificate.

172.30.0.0/16 is the default value of the servicesSubnet variable in the master-config.yaml file. If this has changed, then the --insecure-registry value in the above step should be adjusted to match, as it is indicating the subnet for the registry to use. Note that the openshift_portal_net variable can be set in the Ansible inventory file and used during the advanced installation method to modify the servicesSubnet variable.

After the initial OpenShift Container Platform installation is complete, you can choose to secure the integrated Docker registry, which involves adjusting the --insecure-registry option accordingly.

Configuring Docker Storage

Containers and the images they are created from are stored in Docker’s storage back end. This storage is ephemeral and separate from any persistent storage allocated to meet the needs of your applications.

For RHEL Atomic Host

The default storage back end for Docker on RHEL Atomic Host is a thin pool logical volume, which is supported for production environments. You must ensure that enough space is allocated for this volume per the Docker storage requirements mentioned in System Requirements.

If you do not have enough allocated, see Managing Storage with Docker Formatted Containers for details on using docker-storage-setup and basic instructions on storage management in RHEL Atomic Host.

For RHEL

The default storage back end for Docker on RHEL 7 is a thin pool on loopback devices, which is not supported for production use and only appropriate for proof of concept environments. For production environments, you must create a thin pool logical volume and re-configure Docker to use that volume.

You can use the docker-storage-setup script included with Docker to create a thin pool device and configure Docker’s storage driver. This can be done after installing Docker and should be done before creating images or containers. The script reads configuration options from the /etc/sysconfig/docker-storage-setup file and supports three options for creating the logical volume:

  • Option A) Use an additional block device.

  • Option B) Use an existing, specified volume group.

  • Option C) Use the remaining free space from the volume group where your root file system is located.

Option A is the most robust option, however it requires adding an additional block device to your host before configuring Docker storage. Options B and C both require leaving free space available when provisioning your host. Option C is known to cause issues with some applications, for example Red Hat Mobile Application Platform (RHMAP).

  1. Create the docker-pool volume using one of the following three options:

    • Option A) Use an additional block device.

      In /etc/sysconfig/docker-storage-setup, set DEVS to the path of the block device you wish to use. Set VG to the volume group name you wish to create; docker-vg is a reasonable choice. For example:

      # cat <<EOF > /etc/sysconfig/docker-storage-setup
DEVS=/dev/vdc
VG=docker-vg
EOF

      Then run docker-storage-setup and review the output to ensure the docker-pool volume was created:

      # docker-storage-setup                                                                                                                                                                                                                                [5/1868]
0
Checking that no-one is using this disk right now ...
OK

Disk /dev/vdc: 31207 cylinders, 16 heads, 63 sectors/track
sfdisk:  /dev/vdc: unrecognized partition table type

Old situation:
sfdisk: No partitions found

New situation:
Units: sectors of 512 bytes, counting from 0

   Device Boot    Start       End   #sectors  Id  System
/dev/vdc1          2048  31457279   31455232  8e  Linux LVM
/dev/vdc2             0         -          0   0  Empty
/dev/vdc3             0         -          0   0  Empty
/dev/vdc4             0         -          0   0  Empty
Warning: partition 1 does not start at a cylinder boundary
Warning: partition 1 does not end at a cylinder boundary
Warning: no primary partition is marked bootable (active)
This does not matter for LILO, but the DOS MBR will not boot this disk.
Successfully wrote the new partition table

Re-reading the partition table ...

If you created or changed a DOS partition, /dev/foo7, say, then use dd(1)
to zero the first 512 bytes:  dd if=/dev/zero of=/dev/foo7 bs=512 count=1
(See fdisk(8).)
  Physical volume "/dev/vdc1" successfully created
  Volume group "docker-vg" successfully created
  Rounding up size to full physical extent 16.00 MiB
  Logical volume "docker-poolmeta" created.
  Logical volume "docker-pool" created.
  WARNING: Converting logical volume docker-vg/docker-pool and docker-vg/docker-poolmeta to pool's data and metadata volumes.
  THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)
  Converted docker-vg/docker-pool to thin pool.
  Logical volume "docker-pool" changed.

    • Option B) Use an existing, specified volume group.

      In /etc/sysconfig/docker-storage-setup, set VG to the desired volume group. For example:

      # cat <<EOF > /etc/sysconfig/docker-storage-setup
VG=docker-vg
EOF

      Then run docker-storage-setup and review the output to ensure the docker-pool volume was created:

      # docker-storage-setup
  Rounding up size to full physical extent 16.00 MiB
  Logical volume "docker-poolmeta" created.
  Logical volume "docker-pool" created.
  WARNING: Converting logical volume docker-vg/docker-pool and docker-vg/docker-poolmeta to pool's data and metadata volumes.
  THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)
  Converted docker-vg/docker-pool to thin pool.
  Logical volume "docker-pool" changed.

    • Option C) Use the remaining free space from the volume group where your root file system is located.

      Verify that the volume group where your root file system resides has the desired free space, then run docker-storage-setup and review the output to ensure the docker-pool volume was created:

      # docker-storage-setup
  Rounding up size to full physical extent 32.00 MiB
  Logical volume "docker-poolmeta" created.
  Logical volume "docker-pool" created.
  WARNING: Converting logical volume rhel/docker-pool and rhel/docker-poolmeta to pool's data and metadata volumes.
  THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)
  Converted rhel/docker-pool to thin pool.
  Logical volume "docker-pool" changed.

  2. Verify your configuration. You should have a dm.thinpooldev value in the /etc/sysconfig/docker-storage file and a docker-pool logical volume:

    # cat /etc/sysconfig/docker-storage
DOCKER_STORAGE_OPTIONS=--storage-opt dm.fs=xfs --storage-opt
dm.thinpooldev=/dev/mapper/docker--vg-docker--pool

# lvs
  LV          VG   Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  docker-pool rhel twi-a-t---  9.29g             0.00   0.12

    Before using Docker or OpenShift Container Platform, verify that the docker-pool logical volume is large enough to meet your needs. The docker-pool volume should be 60% of the available volume group and will grow to fill the volume group via LVM monitoring.

  3. Check if Docker is running:

    # systemctl is-active docker

  4. If Docker has not yet been started on the host, enable and start the service:

    # systemctl enable docker
# systemctl start docker

    If Docker is already running, re-initialize Docker:

    This will destroy any containers or images currently on the host.

    		 
    # systemctl stop docker
# rm -rf /var/lib/docker/*
# systemctl restart docker

    If there is any content in /var/lib/docker/, it must be deleted. Files will be present if Docker has been used prior to the installation of OpenShift Container Platform.

Reconfiguring Docker Storage

Should you need to reconfigure Docker storage after having created the docker-pool, you should first remove the docker-pool logical volume. If you are using a dedicated volume group, you should also remove the volume group and any associated physical volumes before reconfiguring docker-storage-setup according to the instructions above.

See Logical Volume Manager Administration for more detailed information on LVM management.

Managing Container Logs

Sometimes a container’s log file (the /var/lib/docker/containers/<hash>/<hash>-json.log file on the node where the container is running) can increase to a problematic size. You can manage this by configuring Docker’s json-file logging driver to restrict the size and number of log files.

Aggregated logging is only supported using the journald driver in Docker. See Updating Fluentd’s Log Source After a Docker Log Driver Update for more information.
Option Purpose

--log-opt max-size

Sets the size at which a new log file is created.

--log-opt max-file

Sets the file on each host to configure the options.

For example, to set the maximum file size to 1MB and always keep the last three log files, edit the /etc/sysconfig/docker file to configure max-size=1M and max-file=3:

OPTIONS='--insecure-registry=172.30.0.0/16 --selinux-enabled --log-opt max-size=1M --log-opt max-file=3'

Next, restart the Docker service:

# systemctl restart docker

Viewing Available Container Logs

Container logs are stored in the /var/lib/docker/containers/<hash>/ directory on the node where the container is running. For example:

# ls -lh /var/lib/docker/containers/f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8/
total 2.6M
-rw-r--r--. 1 root root 5.6K Nov 24 00:12 config.json
-rw-r--r--. 1 root root 649K Nov 24 00:15 f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8-json.log
-rw-r--r--. 1 root root 977K Nov 24 00:15 f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8-json.log.1
-rw-r--r--. 1 root root 977K Nov 24 00:15 f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8-json.log.2
-rw-r--r--. 1 root root 1.3K Nov 24 00:12 hostconfig.json
drwx------. 2 root root    6 Nov 24 00:12 secrets

See Docker’s documentation for additional information on how to configure logging drivers.

Blocking Local Volume Usage

When a volume is provisioned using the VOLUME instruction in a Dockerfile or using the docker run -v <volumename> command, a host’s storage space is used. Using this storage can lead to an unexpected out of space issue and could bring down the host.

In OpenShift Container Platform, users trying to run their own images risk filling the entire storage space on a node host. One solution to this issue is to prevent users from running images with volumes. This way, the only storage a user has access to can be limited, and the cluster administrator can assign storage quota.

Using docker-novolume-plugin solves this issue by disallowing starting a container with local volumes defined. In particular, the plug-in blocks docker run commands that contain:

  • The --volumes-from option

  • Images that have VOLUME(s) defined

  • References to existing volumes that were provisioned with the docker volume command

The plug-in does not block references to bind mounts.

To enable docker-novolume-plugin, perform the following steps on each node host:

  1. Install the docker-novolume-plugin package:

    $ yum install docker-novolume-plugin

  2. Enable and start the docker-novolume-plugin service:

    $ systemctl enable docker-novolume-plugin
$ systemctl start docker-novolume-plugin

  3. Edit the /etc/sysconfig/docker file and append the following to the OPTIONS list:

    --authorization-plugin=docker-novolume-plugin

  4. Restart the docker service:

    $ systemctl restart docker

After you enable this plug-in, containers with local volumes defined fail to start and show the following error message:

runContainer: API error (500): authorization denied by plugin
docker-novolume-plugin: volumes are not allowed

Ensuring Host Access

The quick and advanced installation methods require a user that has access to all hosts. If you want to run the installer as a non-root user, passwordless sudo rights must be configured on each destination host.

For example, you can generate an SSH key on the host where you will invoke the installation process:

# ssh-keygen

Do not use a password.

An easy way to distribute your SSH keys is by using a bash loop:

# for host in master.example.com \
    node1.example.com \
    node2.example.com; \
    do ssh-copy-id -i ~/.ssh/id_rsa.pub $host; \
    done

Modify the host names in the above command according to your configuration.

Setting Global Proxy Values

The OpenShift Container Platform installer uses the proxy settings in the _/etc/environment _ file.

Ensure the following domain suffixes and IP addresses are in the /etc/environment file in the no_proxy parameter:

  • Master and node host names (domain suffix).

  • Other internal host names (domain suffix).

  • Etcd IP addresses (must be IP addresses and not host names, as etcd access is done by IP address).

  • Docker registry IP address.

  • Kubernetes IP address, by default 172.30.0.1. Must be the value set in the openshift_portal_net parameter in the Ansible inventory file, by default /etc/ansible/hosts.

  • Kubernetes internal domain suffix: cluster.local.

  • Kubernetes internal domain suffix: .svc.

The following example assumes http_proxy and https_proxy values are set:

no_proxy=.internal.example.com,10.0.0.1,10.0.0.2,10.0.0.3,.cluster.local,.svc,localhost,127.0.0.1,172.30.0.1

Because noproxy does not support CIDR, you can use domain suffixes.

What’s Next?

If you are interested in installing OpenShift Container Platform using the containerized method (optional for RHEL but required for RHEL Atomic Host), see Installing on Containerized Hosts to prepare your hosts.

When you are ready to proceed, you can install OpenShift Container Platform using the quick installation or advanced installation method.

If you are installing a stand-alone registry, continue with Installing a Stand-alone Registry.