kata-containers/Developer-Guide.md

• Warning
• Assumptions
• Initial setup
• Requirements to build individual components
• Build and install the Kata Containers runtime
  • Check hardware requirements
  • Configure to use initrd or rootfs image
  • Enable full debug
• Build and install Kata proxy
• Build and install Kata shim
• Create and install rootfs and initrd image
  • Build a custom Kata agent - OPTIONAL
  • Get the osbuilder
  • Create a rootfs image
    • Create a local rootfs
    • Add a custom agent to the image - OPTIONAL
    • Build a rootfs image
    • Install the rootfs image
  • Create an initrd image - OPTIONAL
    • Create a local rootfs for initrd image
    • Build an initrd image
    • Install the initrd image
• Install guest kernel images
• Run Kata Containers with Docker
  • Update Docker configuration
  • Create a container using Kata
• Run Kata Containers with Kubernetes
  • Install a CRI implementation
    • CRI-O
    • CRI-containerd
  • Install Kubernetes
    • Configure for CRI-O
    • Configure for CRI-containerd
  • Run a Kubernetes pod with Kata Containers
• Troubleshoot Kata Containers
• Appendices
  • Checking Docker default runtime
  • Set up a debug console
    • Create a custom image containing a shell
    • Create a debug systemd service
    • Build the debug image
    • Configure runtime for custom debug image
    • Ensure debug options are valid
    • Create a container
    • Connect to the virtual machine using the debug console
    • Obtain details of the image

Warning

This document is written specifically for developers: it is not intended for end users.

Assumptions

• You are working on a non-critical test or development system.

Initial setup

The recommended way to create a development environment is to first install the packaged versions of the Kata Containers components to create a working system.

The installation guide instructions will install all required Kata Containers components, plus Docker*, the hypervisor, and the Kata Containers image and guest kernel.

Requirements to build individual components

You need to install the following to build Kata Containers components:

• golang version 1.8.3 or newer.

  To view the versions of go known to work, see the golang entry in the versions database.

• make.

• gcc (required for building the shim and runtime).

Build and install the Kata Containers runtime

$ go get -d -u github.com/kata-containers/runtime
$ cd $GOPATH/src/github.com/kata-containers/runtime
$ make && sudo -E PATH=$PATH make install

The build will create the following:

• runtime binary: /usr/local/bin/kata-runtime
• configuration file: /usr/share/defaults/kata-containers/configuration.toml

Check hardware requirements

You can check if your system is capable of creating a Kata Container by running the following:

$ sudo kata-runtime kata-check

If your system is not able to run Kata Containers, the previous command will error out and explain why.

Configure to use initrd or rootfs image

Kata containers can run with either an initrd image or a rootfs image.

If you want to test with initrd, make sure you have initrd = /usr/share/kata-containers/kata-containers-initrd.img in /usr/share/defaults/kata-containers/configuration.toml and comment out the image line with the following:

$ sudo sed -i 's/^\(image =.*\)/# \1/g' /usr/share/defaults/kata-containers/configuration.toml

You can create the initrd image as shown in the create an initrd image section.

If you want to test with a rootfs image, make sure you have image = /usr/share/kata-containers/kata-containers.img in /usr/share/defaults/kata-containers/configuration.toml and comment out the initrd line with the following:

$ sudo sed -i 's/^\(initrd =.*\)/# \1/g' /usr/share/defaults/kata-containers/configuration.toml

The rootfs image is created as shown in the create a rootfs image section.

One of the initrd and image options in kata runtime config file MUST be set but not both. The main difference between the options is that the size of initrd(10MB+) is significantly smaller than rootfs image(100MB+).

Enable full debug

Enable full debug as follows:

$ sudo sed -i -e 's/^# *\(enable_debug\).*=.*$/\1 = true/g' /usr/share/defaults/kata-containers/configuration.toml
$ sudo sed -i -e 's/^kernel_params = "\(.*\)"/kernel_params = "\1 agent.log=debug"/g' /usr/share/defaults/kata-containers/configuration.toml

Build and install Kata proxy

$ go get -d -u github.com/kata-containers/proxy
$ cd $GOPATH/src/github.com/kata-containers/proxy && make && sudo make install

Build and install Kata shim

$ go get -d -u github.com/kata-containers/shim
$ cd $GOPATH/src/github.com/kata-containers/shim && make && sudo make install

Create and install rootfs and initrd image

Build a custom Kata agent - OPTIONAL

Note:

• You should only do this step if you are testing with the latest version of the agent.

$ go get -d -u github.com/kata-containers/agent
$ cd $GOPATH/src/github.com/kata-containers/agent && make

Get the osbuilder

$ go get -d -u github.com/kata-containers/osbuilder

Create a rootfs image

Create a local rootfs

As a prerequisite, you need to install Docker. Otherwise, you will not be able to run the rootfs.sh script with USE_DOCKER=true as expected in the following example.

$ export ROOTFS_DIR=${GOPATH}/src/github.com/kata-containers/osbuilder/rootfs-builder/rootfs
$ sudo rm -rf ${ROOTFS_DIR}
$ cd $GOPATH/src/github.com/kata-containers/osbuilder/rootfs-builder
$ script -fec 'sudo -E GOPATH=$GOPATH USE_DOCKER=true ./rootfs.sh ${distro}'

You MUST choose one of alpine, centos, clearlinux, euleros, and fedora for ${distro}.

Note:

• You must ensure that the default Docker runtime is runc to make use of the USE_DOCKER variable. If that is not the case, remove the variable from the previous command. See Checking Docker default runtime.

Add a custom agent to the image - OPTIONAL

Note:

• You should only do this step if you are testing with the latest version of the agent.

$ sudo install -o root -g root -m 0550 -t ${ROOTFS_DIR}/bin ../../agent/kata-agent
$ sudo install -o root -g root -m 0440 ../../agent/kata-agent.service ${ROOTFS_DIR}/usr/lib/systemd/system/
$ sudo install -o root -g root -m 0440 ../../agent/kata-containers.target ${ROOTFS_DIR}/usr/lib/systemd/system/

Build a rootfs image

$ cd $GOPATH/src/github.com/kata-containers/osbuilder/image-builder
$ script -fec 'sudo -E USE_DOCKER=true ./image_builder.sh ${ROOTFS_DIR}'

Notes:

• You must ensure that the default Docker runtime is runc to make use of the USE_DOCKER variable. If that is not the case, remove the variable from the previous command. See Checking Docker default runtime.
• If you do not wish to build under Docker, remove the USE_DOCKER variable in the previous command and ensure the qemu-img command is available on your system.

Install the rootfs image

$ commit=$(git log --format=%h -1 HEAD)
$ date=$(date +%Y-%m-%d-%T.%N%z)
$ image="kata-containers-${date}-${commit}"
$ sudo install -o root -g root -m 0640 -D kata-containers.img "/usr/share/kata-containers/${image}"
$ (cd /usr/share/kata-containers && sudo ln -sf "$image" kata-containers.img)

Create an initrd image - OPTIONAL

Create a local rootfs for initrd image

$ export ROOTFS_DIR="${GOPATH}/src/github.com/kata-containers/osbuilder/rootfs-builder/rootfs"
$ sudo rm -rf ${ROOTFS_DIR}
$ cd $GOPATH/src/github.com/kata-containers/osbuilder/rootfs-builder
$ script -fec 'sudo -E GOPATH=$GOPATH AGENT_INIT=yes USE_DOCKER=true ./rootfs.sh ${distro}'

AGENT_INIT controls if the guest image uses kata agent as the guest init process. When you create an initrd image, always set AGENT_INIT to yes.

You MUST choose one of alpine, centos, clearlinux, euleros, and fedora for ${distro}.

Optionally, add your custom agent binary to the rootfs with the following:

$ sudo install -o root -g root -m 0550 -T ../../agent/kata-agent ${ROOTFS_DIR}/sbin/init

Build an initrd image

$ cd $GOPATH/src/github.com/kata-containers/osbuilder/initrd-builder
$ script -fec 'sudo -E AGENT_INIT=yes USE_DOCKER=true ./initrd_builder.sh ${ROOTFS_DIR}'

Install the initrd image

$ commit=$(git log --format=%h -1 HEAD)
$ date=$(date +%Y-%m-%d-%T.%N%z)
$ image="kata-containers-initrd-${date}-${commit}"
$ sudo install -o root -g root -m 0640 -D kata-containers-initrd.img "/usr/share/kata-containers/${image}"
$ (cd /usr/share/kata-containers && sudo ln -sf "$image" kata-containers-initrd.img)

Install guest kernel images

As a prerequisite, you need to install libelf-dev and bc. Otherwise, you will not be able to build the kernel from sources.

$ go get github.com/kata-containers/tests
$ cd $GOPATH/src/github.com/kata-containers/tests/.ci
$ kernel_arch="$(./kata-arch.sh)"
$ kernel_dir="$(./kata-arch.sh --kernel)"
$ tmpdir="$(mktemp -d)"
$ pushd "$tmpdir"
$ curl -L https://raw.githubusercontent.com/kata-containers/packaging/master/kernel/configs/${kernel_arch}_kata_kvm_4.14.x -o .config
$ kernel_version=$(grep "Linux/[${kernel_arch}]*" .config | cut -d' ' -f3 | tail -1)
$ kernel_tar_file="linux-${kernel_version}.tar.xz"
$ kernel_url="https://cdn.kernel.org/pub/linux/kernel/v$(echo $kernel_version | cut -f1 -d.).x/${kernel_tar_file}"
$ curl -LOk ${kernel_url}
$ tar -xf ${kernel_tar_file}
$ mv .config "linux-${kernel_version}"
$ pushd "linux-${kernel_version}"
$ curl -L https://raw.githubusercontent.com/kata-containers/packaging/master/kernel/patches/0001-NO-UPSTREAM-9P-always-use-cached-inode-to-fill-in-v9.patch | patch -p1
$ make ARCH=${kernel_dir} -j$(nproc)
$ kata_kernel_dir="/usr/share/kata-containers"
$ kata_vmlinuz="${kata_kernel_dir}/kata-vmlinuz-${kernel_version}.container"
$ [ $kernel_arch = ppc64le ] && kernel_file="$(realpath ./vmlinux)" || kernel_file="$(realpath arch/${kernel_arch}/boot/bzImage)"
$ sudo install -o root -g root -m 0755 -D "${kernel_file}" "${kata_vmlinuz}"
$ sudo ln -sf "${kata_vmlinuz}" "${kata_kernel_dir}/vmlinuz.container"
$ kata_vmlinux="${kata_kernel_dir}/kata-vmlinux-${kernel_version}"
$ sudo install -o root -g root -m 0755 -D "$(realpath vmlinux)" "${kata_vmlinux}"
$ sudo ln -sf "${kata_vmlinux}" "${kata_kernel_dir}/vmlinux.container"
$ popd
$ popd
$ rm -rf "${tmpdir}"

Run Kata Containers with Docker

Update Docker configuration

$ dir=/etc/systemd/system/docker.service.d
$ file="$dir/kata-containers.conf"
$ sudo mkdir -p "$dir"
$ sudo test -e "$file" || echo -e "[Service]\nType=simple\nExecStart=\nExecStart=/usr/bin/dockerd -D --default-runtime runc" | sudo tee "$file"
$ sudo grep -q "kata-runtime=" $file || sudo sed -i 's!^\(ExecStart=[^$].*$\)!\1 --add-runtime kata-runtime=/usr/local/bin/kata-runtime!g' "$file"
$ sudo systemctl daemon-reload
$ sudo systemctl restart docker

Create a container using Kata

$ sudo docker run -ti --runtime kata-runtime busybox sh

Run Kata Containers with Kubernetes

Now that Kata Containers is installed on your system, you need some extra components to make this work with Kubernetes.

Install a CRI implementation

Kata Containers runtime is an OCI compatible runtime and cannot directly interact with the CRI API level. For this reason we rely on a CRI implementation to translate CRI into OCI. There are two supported ways called CRI-O and CRI-containerd. It is up to you to choose the one that you want, but you have to pick one. After choosing either CRI-O or CRI-containerd, you must make the appropriate changes to ensure it relies on the Kata Containers runtime.

CRI-O

If you select CRI-O, follow the "CRI-O Tutorial" instructions here to properly install it.

Once you have installed CRI-O, you need to modify the CRI-O configuration with information about different container runtimes. By default, we choose runc, but in this case we also specify Kata Containers runtime to run untrusted workloads. In other words, this defines an alternative runtime to be used when the workload cannot be trusted and a higher level of security is required. An additional flag can be used to let CRI-O know if a workload should be considered trusted or untrusted by default. For further details, see the documentation here.

Additionally, we need CRI-O to perform the network namespace management. Otherwise, when the VM starts the network will not be available.

The following is an example of how to modify the /etc/crio/crio.conf file in order to apply the previous explanations, and therefore get Kata Containers runtime to invoke by CRI-O.

# The "crio.runtime" table contains settings pertaining to the OCI
# runtime used and options for how to set up and manage the OCI runtime.
[crio.runtime]
manage_network_ns_lifecycle = true

# runtime is the OCI compatible runtime used for trusted container workloads.
# This is a mandatory setting as this runtime will be the default one
# and will also be used for untrusted container workloads if
# runtime_untrusted_workload is not set.
runtime = "/usr/bin/runc"

# runtime_untrusted_workload is the OCI compatible runtime used for untrusted
# container workloads. This is an optional setting, except if
# default_container_trust is set to "untrusted".
runtime_untrusted_workload = "/usr/bin/kata-runtime"

# default_workload_trust is the default level of trust crio puts in container
# workloads. It can either be "trusted" or "untrusted", and the default
# is "trusted".
# Containers can be run through different container runtimes, depending on
# the trust hints we receive from kubelet:
# - If kubelet tags a container workload as untrusted, crio will try first to
# run it through the untrusted container workload runtime. If it is not set,
# crio will use the trusted runtime.
# - If kubelet does not provide any information about the container workload trust
# level, the selected runtime will depend on the default_container_trust setting.
# If it is set to "untrusted", then all containers except for the host privileged
# ones, will be run by the runtime_untrusted_workload runtime. Host privileged
# containers are by definition trusted and will always use the trusted container
# runtime. If default_container_trust is set to "trusted", crio will use the trusted
# container runtime for all containers.
default_workload_trust = "untrusted"

Restart CRI-O to take changes into account

$ sudo systemctl restart crio

CRI-containerd

If you select CRI-containerd, follow the "Getting Started for Developers" instructions here to properly install it.

To customize CRI-containerd to select Kata Containers runtime, follow our "Configure containerd to use Kata Containers" internal documentation here.

Install Kubernetes

Depending on what your needs are and what you expect to do with Kubernetes, please refer to the following documentation to install it correctly.

Kubernetes talks with CRI implementations through a container-runtime-endpoint, also called CRI socket. This socket path is different depending on which CRI implementation you chose, and the kubelet service has to be updated accordingly.

Configure for CRI-O

/etc/systemd/system/kubelet.service.d/0-crio.conf

[Service]                                                 
Environment="KUBELET_EXTRA_ARGS=--container-runtime=remote --runtime-request-timeout=15m --container-runtime-endpoint=unix:///var/run/crio/crio.sock"

Configure for CRI-containerd

/etc/systemd/system/kubelet.service.d/0-cri-containerd.conf

[Service]                                                 
Environment="KUBELET_EXTRA_ARGS=--container-runtime=remote --runtime-request-timeout=15m --container-runtime-endpoint=unix:///run/containerd/containerd.sock"

For more information about CRI-containerd see the "Configure Kubelet to use containerd" documentation here.

Run a Kubernetes pod with Kata Containers

After you update your kubelet service based on the CRI implementation you are using, reload and restart kubelet. Then, start your cluster:

$ sudo systemctl daemon-reload
$ sudo systemctl restart kubelet

# If using CRI-O
$ sudo kubeadm init --skip-preflight-checks --cri-socket /var/run/crio/crio.sock --pod-network-cidr=10.244.0.0/16

# If using CRI-containerd
$ sudo kubeadm init --skip-preflight-checks --cri-socket /run/containerd/containerd.sock --pod-network-cidr=10.244.0.0/16

$ export KUBECONFIG=/etc/kubernetes/admin.conf

You can force kubelet to use Kata Containers by adding some untrusted annotation to your pod configuration. In our case, this ensures Kata Containers is the selected runtime to run the described workload.

nginx-untrusted.yaml

apiVersion: v1
kind: Pod
metadata:
  name: nginx-untrusted
  annotations:
    io.kubernetes.cri.untrusted-workload: "true"
spec:
  containers:
    name: nginx
    image: nginx

Next, you run your pod:

$ sudo -E kubectl apply -f nginx-untrusted.yaml

Troubleshoot Kata Containers

If you are unable to create a Kata Container first ensure you have enabled full debug before attempting to create a container. Then run the kata-collect-data.sh script and paste its output directly into a github issue.

Note:

The kata-collect-data.sh script is built from the runtime repository.

To perform analysis on Kata logs, use the kata-log-parser tool, which can convert the logs into formats (e.g. JSON, TOML, XML, and YAML).

To obtain a full backtrace for the agent, proxy, runtime, or shim send the SIGUSR1 signal to the process ID of the component. The component will send a backtrace to the system log on the host system and continue to run without interruption.

For example, to obtain a backtrace for kata-proxy:

$ sudo kill -USR1 $kata_proxy_pid
$ sudo journalctl -t kata-proxy

See Set up a debug console.

Appendices

Checking Docker default runtime

$ sudo docker info 2>/dev/null | grep -i "default runtime" | cut -d: -f2- | grep -q runc  && echo "SUCCESS" || echo "ERROR: Incorrect default Docker runtime"

Set up a debug console

By default you cannot login to a virtual machine since this can be sensitive from a security perspective. Also allowing logins would require additional packages in the rootfs, which would increase the size of the image used to boot the virtual machine.

If you want to login to a virtual machine that hosts your containers, complete the following steps, which assume a rootfs image.

Create a custom image containing a shell

To login to a virtual machine, you must create a custom rootfs containing a shell such as bash(1).

For example using CentOS:

$ cd $GOPATH/src/github.com/kata-containers/osbuilder/rootfs-builder
$ export ROOTFS_DIR=${GOPATH}/src/github.com/kata-containers/osbuilder/rootfs-builder/rootfs
$ script -fec 'sudo -E GOPATH=$GOPATH USE_DOCKER=true EXTRA_PKGS="bash" ./rootfs.sh centos'

Create a debug systemd service

Create the service file that starts the shell in the rootfs directory:

$ cat <<EOT | sudo tee ${ROOTFS_DIR}/lib/systemd/system/kata-debug.service
[Unit]
Description=Kata Containers debug console

[Service]
Environment=PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
StandardInput=tty
StandardOutput=tty
PrivateDevices=yes
Type=simple
ExecStart=/usr/bin/bash
Restart=always
EOT

Note: You might need to adjust the ExecStart= path.

Add a dependency to start the debug console:

$ sudo sed -i '$a Requires=kata-debug.service' ${ROOTFS_DIR}/lib/systemd/system/kata-containers.target

Build the debug image

Follow the instructions in the Build a rootfs image section.

Configure runtime for custom debug image

Install the image:

$ name="kata-containers-centos-with-debug-console.img"
$ sudo install -o root -g root -m 0640 kata-containers.img "/usr/share/kata-containers/${name}"

Next, modify the image= values in the [hypervisor.qemu] section of the configuration file to specify the full path to the image name specified in the previous code section. Alternatively, recreate the symbolic link so it points to the new debug image:

$ (cd /usr/share/kata-containers && sudo ln -sf "$name" kata-containers.img)

Note: You should take care to undo this change after you finish debugging to avoid all subsequently created containers from using the debug image.

Ensure debug options are valid

For the debug console to work, you must ensure that proxy debug is disabled in the configuration file. If proxy debug is enabled, you will not see any output when you connect to the virtual machine:

$ sudo awk '{if (/^\[proxy\.kata\]/) {got=1}; if (got == 1 && /^.*enable_debug/) {print "#enable_debug = true"; got=0; next; } else {print}}' /usr/share/defaults/kata-containers/configuration.toml > /tmp/configuration.toml
$ sudo install -o root -g root -m 0640 /tmp/configuration.toml /usr/share/defaults/kata-containers/configuration.toml

Create a container

Create a container as normal. For example using Docker:

$ sudo docker run -ti busybox sh

Connect to the virtual machine using the debug console

$ id=$(sudo docker ps -q --no-trunc)
$ console="/var/run/vc/sbs/${id}/console.sock"
$ sudo socat "stdin,raw,echo=0,escape=0x11" "unix-connect:${console}"

Note: You need to press the RETURN key to see the shell prompt.

To disconnect from the virtual machine, type CONTROL+q (hold down the CONTROL key and press q).

Obtain details of the image

If the image is created using osbuilder, the following YAML file exists and contains details of the image and how it was created:

$ cat /var/lib/osbuilder/osbuilder.yaml