Configure the system to use the Unbreakable Enterprise Kernel Release 5 (UEK R5) or later and boot the system with this kernel. If you are using an earlier Unbreakable Enterprise Kernel (UEK) release, or the Red Hat Compatible Kernel (RHCK), you must upgrade the kernel.

To install or update UEK:

1. If your system is registered with ULN, disable access to the ol7_x86_64_UEKR3 and ol7_x86_64_UEKR4 channels, and enable access to the ol7_x86_64_UEKR5 channel.

   Log into https://linux.oracle.com with your ULN user name and password and click on the Systems tab to select the system where you installing Oracle Container Runtime for Docker. Go to the Manage Subscriptions page and update the channel subscriptions for the system. Click on Save Subscriptions to save your changes.

2. If you use the Oracle Linux yum server, disable the ol7_UEKR3 and ol7_UEKR4 repositories and enable the ol7_UEKR5 repository. You can do this easily using yum-config-manager:

   sudo yum-config-manager --disable ol7_UEKR3 ol7_UEKR4
   sudo yum-config-manager --enable ol7_UEKR5                     

3. Run the following command to upgrade the system to the selected UEK release:

   sudo yum update                     

4. Reboot the system, selecting UEK if this is not the default boot kernel.

   sudo systemctl reboot                     

To access to the Oracle Container Runtime for Docker packages, you must enable the appropriate ULN channel or yum repositories.

If your system is registered with ULN, enable the ol7_x86_64_addons channel. Use the ULN web interface to subscribe the system to the appropriate channel:

1. Log in to https://linux.oracle.com with your ULN user name and password.

2. On the Systems tab, click the link named for the system in the list of registered machines.

3. On the System Details page, click Manage Subscriptions.

4. On the System Summary page, select each required channel from the list of available channels and click the right arrow to move the channel to the list of subscribed channels.

   Subscribe the system to the ol7_x86_64_addons channel.

5. Click Save Subscriptions.

If you use the Oracle Linux yum server, enable the ol7_addons channel. To enable a yum repository on your system, use the yum-config-manager command. For example, run:

sudo yum-config-manager --enable ol7_addons               

The latest Docker package is docker-engine, which conflicts with the older docker package. If you have the older docker package installed, you must remove it before you install Docker Engine. To check if you have the older docker package installed, run:

sudo rpm -qi docker               

If the older docker package is installed, stop the docker service and remove the package. To stop the docker service:

sudo systemctl stop docker               

Remove the docker package.

sudo yum remove docker               

You can now install the docker-engine package.

To install the docker-engine and docker-cli packages.

sudo yum install docker-engine docker-cli               

Start the docker service and configure it to start at boot time.

sudo systemctl enable --now docker               

To check that the docker service is running, use the following command:

sudo systemctl status docker               

You can also use the docker info command to display information about the configuration and version of the Docker Engine.

sudo docker info               

For more information, see the docker(1) manual page.

To configure web proxy networking options, create the drop-in file /etc/systemd/system/docker.service.d/http-proxy.conf that contains the following lines:

[Service]
Environment="HTTP_PROXY=proxy_URL:port"
Environment="HTTPS_PROXY=proxy_URL:port"

Replace proxy_URL and port with the appropriate URLs and port numbers for your web proxy.

After adding or modifying a systemd drop-in file while the docker service is running, you need to tell systemd to reload the configuration for the service.

sudo systemctl daemon-reload               

Restart the docker service for the configuration changes to take effect.

sudo systemctl restart docker               

With IPv6 enabled, Docker assigns the link-local IPv6 address fe80::1 to the bridge docker0.

For more information about configuring Docker networking, see:

https://docs.docker.com/engine/userguide/networking/

To configure IPv6 networking:

1. Create or edit /etc/docker/daemon.json.

   If you are creating this file from scratch, it should look like this:

   {
     "ipv6": true
   }

   If this file already exists and contains other entries, be careful that adding a line for the ipv6 configuration variable conforms with typical JSON formatting.

   If you want Docker to assign global IPv6 addresses to containers, additionally specify the IPv6 subnet for the fixed-cidr-v6 option, for example:

   {
     "ipv6": true,
     "fixed-cidr-v6": "2001:db8:1::/64"
   }

   Similarly, you can also configure the default IPv6 gateway that should be used by Docker, using the default-gateway-v6 parameter in this configuration file.

   For more information on the format and options for this configuration file, see:

   https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file

2. Check that the --ipv6, --fixed-cidr-v6 and default-gateway-v6 options are not being invoked as command line switches when starting the Docker engine daemon.

   You should check that these options do not appear in either the /etc/sysconfig/docker or /etc/sysconfig/docker-networking files. These files are deprecated and may be removed in future releases. If these files contain any other configuration parameters, consider whether you could move these into /etc/docker/daemon.json to future-proof your configuration.

   Also check that these options do not appear in any systemd drop-in files in /etc/systemd/system/docker.service.d/. While this is a supported configuration option, it is preferable to keep all Docker Engine configuration in the same place, where possible.

The Docker Engine is configured to use overlay2 as the default storage driver to manage Docker containers. This provides a performance and scalability improvement on earlier releases that used the device mapper as the default storage driver, but the technology is new and should be tested properly before use in production environments. For more information on overlay2, see:

https://docs.docker.com/engine/userguide/storagedriver/overlayfs-driver/

Overlay file systems can corrupt when used in conjunction with any file system that does not have dtype support enabled.

The Docker Engine installer checks the filesystem for dtype support, and if this is not enabled, the default storage driver is set to use devicemapper. This check is only performed on a fresh installation of Docker Engine. The configuration of an existing Docker installation is unaffected during upgrade.

This allows Docker to function on a default Oracle Linux 7 system without any additional configuration required, immediately after install. However, using the devicemapper is not recommended for production environments. Performance and scalability can be compromised by this configuration. Therefore, it is important to consider using dedicated storage for Docker, and to change the storage driver to use either btrfs or overlay2.

{
...
"storage-opts" : [ "dm.basesize=50G" ],
...
}

Oracle recommends using Btrfs as a more stable and mature technology than overlayfs.

In most cases, it is advisable to create a dedicated file system to manage Docker containers. This file system can be mounted at /var/lib/docker at boot time, before the Docker service is started.

Any unused block device that is large enough to store several containers is suitable. The suggested minimum size is 1GB but you might require more space to implement complex Docker applications. If the system is a virtual machine, Oracle recommends that you create, partition, and format a new virtual disk. Alternatively, convert an existing ext3 or ext4 file system to Btrfs. For information on converting file systems, see the Oracle^® Linux 7: Administrator's Guide.

If an LVM volume group has available space, you can create a new logical volume and format it as a Btrfs file system.

If you have installed the mlocate package, it is recommended that you modify the PRUNEPATHS entry in /etc/updatedb.conf to prevent updatedb from indexing directories below /var/lib/docker, for example:

PRUNEPATHS="/media /tmp /var/lib/docker /var/spool /var/tmp"

This entry prevents locate from reporting files that belong to Docker containers.