Page Comparison

...

Docker defines a container as a "standard unit of software".  Container images package an application and all of its dependencies enabling it to run quickly and reliably across platforms.  A container is isolated from other processes and other containers running on the same platform unless interfaces are explicitly defined.  Docker containers provide a standard, lightweight and secure virtualization solution when a full hypervisor is overkill.  Unlike hypervisors that virtualize the hardware, containers are lightweight because only the OS is virtualized.  Containers rely on kernel features such as namespaces, cgroups and unionfs.

Docker provides:

• Docker Engine for running containerscontainer runtime
• Docker tools for creating, deploying and managing containers
• Docker Hub repository for hosting container images

This wiki assumes you have a working knowledge of Yocto.  It will walk you through how to build and deploy Docker on Zynq Ultrascale+ with a Yocto flow .  Docker has been tested on the ZCU102.in the following four configurations:

• systemd on a flash filesystem
• systemd on a ramdisk
• sysvinit on a flash filesystem
• sysvinit on a ramdisk

Requirements

1. ZCU102 Eval Board
2. Linux host machine or VM
   1. Install Yocto dependencies or CROPS/Poky-container
   2. Clone Xilinx Yocto and checkout release version
3. Internet access

Testing

...

Releases

rel-v2018.3 (Rocko)

Platforms

ZCU102

meta-virtualization Layer

The Docker recipe is included in the meta-virtualization layer.  The Xilinx Yocto manifest instructs repo to automatically clone meta-virtualization, so there is no need to clone it manually unless you are using a Xilinx an unsupported Yocto flow.  You can verify that the virtualization layer is installed in the sources directory and that it's included in the bblayers.conf.  From this layer we will be building and installing the docker and docker-contrib packages.  We will add this to a Docker machine configuration later.

...

Linux Configuration

The default zcu102 ZCU102 kernel configuration does not have all the required CONFIG options for Docker, so we will need to turn them on through a configuration fragment.  If you don't already have a kernel recipe directory in your layer, create the directory structure as shown below in your custom layer.

...

Next edit the linux-xlnx_%.bbappend file as shown below and add the docker.cfg.  Note the wildcard , "%, is " is used to match any kernel version.

FILESEXTRAPATHS_prepend := "${THISDIR}/cfg:"

SRC_URI_append = " file://docker.cfg"

Add a docker.cfg file in a the cfg directory and add the CONFIG requirements shown in the listing below.  The script from the Moby Project was used to determine these (more on this later).

...

In order to simplify the network manager on an embedded systemssystem, connman is recommended to manage the NICnetwork adapter.  This is completely optional.  Without connman, you will need to setup the networkd service unit configuration files .  You may add connamn using your local.conf or your <machine>.conf.  which is beyond the scope of this wiki.  Last the loglevel was downgraded to level 6 and audit turned off from the kernel command line to reduce console chatter.

# Inherit all the properties from the zcu102-zynqmp machine
require conf/machine/zcu102-zynqmp.conf

# Reuse the fdt for the zcu102 bsp
YAML_DT_BOARD_FLAGS_pn-device-tree = "{BOARD zcu102-rev1.0}"

# Downgrade the loglevel to reduce console chatter and disable audit
KERNEL_BOOTARGS_append_pn-u-boot-zynq-uenv = " loglevel=6 audit=0"

# Include docker and docker-contrib in the image
IMAGE_INSTALL_append = " docker docker-contrib"

# Comment these out to use the default sysvinit
DISTRO = "petalinux-systemd"
IMAGE_INSTALL_append = " connman"

If you want to boot with an initramfs, add the variables in the listing below to your <machine>.conf or local.conf and observe the Ramdisk ramdisk info note below when running Docker.

# Remove wic because it causes circular dependencies with bundled initramfs
IMAGE_FSTYPES_remove = "wic.qemu-sd"
INITRAMFS_IMAGE = "petalinux-image-minimal"
INITRAMFS_IMAGE_BUNDLE = "1"

Distro Configuration (systemd)

...

HDF

...

The bitbake command below assumes you are building a docker-systemd-zcu102-zynqmp.conf machine which includes the configurations for Docker on a ZCU102.  If you are making setting the configurations in your local.conf, then you may target any machine such as zcu102-zynqmp.

...

If you want to build Docker with sysvinit, then you can may create another machine docker-zcu102-zynqmp.conf and comment out the systemd lines as noted in the docker-systemd-zcu102-zynqmp.conf listing above.

...

Docker expects to run from a non-RAM based root filesystem since it uses pivot_root to jail the container.  For that reason it's recommended that you setup an SD card with VFAT and Ext4 partitions.  Once your SD card is partitioned, copy the boot images to the VFAT partition and extract the rootfs to the Ext4 partition.  These images are available in the deploy/images directory of the machine you built.  Copy the images as shown below noting that the VFAT partition is mounted on boot and the Ext4 partition is mounted on rootfs.  This example is using the dtb that is built from the kernel tree.  If you are using a custom HDF, you will want to use the dtb compiled from the DTG and so make sure that uEnv.txt is using the correct dtb.

...