This page shows how to install the kubeadm
toolbox.
For information how to create a cluster with kubeadm once you have performed this installation process,
see the Using kubeadm to Create a Cluster page.
ip link
or ifconfig -a
sudo cat /sys/class/dmi/id/product_uuid
It is very likely that hardware devices will have unique addresses, although some virtual machines may have identical values. Kubernetes uses these values to uniquely identify the nodes in the cluster. If these values are not unique to each node, the installation process may fail.
If you have more than one network adapter, and your Kubernetes components are not reachable on the default route, we recommend you add IP route(s) so Kubernetes cluster addresses go via the appropriate adapter.
Protocol | Direction | Port Range | Purpose | Used By |
---|---|---|---|---|
TCP | Inbound | 6443* | Kubernetes API server | All |
TCP | Inbound | 2379-2380 | etcd server client API | kube-apiserver, etcd |
TCP | Inbound | 10250 | Kubelet API | Self, Control plane |
TCP | Inbound | 10251 | kube-scheduler | Self |
TCP | Inbound | 10252 | kube-controller-manager | Self |
Protocol | Direction | Port Range | Purpose | Used By |
---|---|---|---|---|
TCP | Inbound | 10250 | Kubelet API | Self, Control plane |
TCP | Inbound | 30000-32767 | NodePort Services** | All |
** Default port range for NodePort Services.
Any port numbers marked with * are overridable, so you will need to ensure any custom ports you provide are also open.
Although etcd ports are included in master nodes, you can also host your own etcd cluster externally or on custom ports.
The pod network plugin you use (see below) may also require certain ports to be open. Since this differs with each pod network plugin, please see the documentation for the plugins about what port(s) those need.
Since v1.6.0, Kubernetes has enabled the use of CRI, Container Runtime Interface, by default.
The container runtime used by default is Docker, which is enabled through the built-in
dockershim
CRI implementation inside of the kubelet
.
Other CRI-based runtimes include:
Refer to the CRI installation instructions for more information.
You will install these packages on all of your machines:
kubeadm
: the command to bootstrap the cluster.
kubelet
: the component that runs on all of the machines in your cluster
and does things like starting pods and containers.
kubectl
: the command line util to talk to your cluster.
kubeadm will not install or manage kubelet
or kubectl
for you, so you will
need to ensure they match the version of the Kubernetes control panel you want
kubeadm to install for you. If you do not, there is a risk of a version skew occurring that
can lead to unexpected, buggy behaviour. However, one minor version skew between the
kubelet and the control plane is supported, but the kubelet version may never exceed the API
server version. For example, kubelets running 1.7.0 should be fully compatible with a 1.8.0 API server,
but not vice versa.
Warning: These instructions exclude all Kubernetes packages from any system upgrades. This is because kubeadm and Kubernetes require special attention to upgrade.
For more information on version skews, please read our version skew policy.
apt-get update && apt-get install -y apt-transport-https curl
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF
apt-get update
apt-get install -y kubelet kubeadm kubectl
apt-mark hold kubelet kubeadm kubectl
cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=1
repo_gpgcheck=1
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
exclude=kube*
EOF
# Set SELinux in permissive mode (effectively disabling it)
setenforce 0
sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config
yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
systemctl enable kubelet && systemctl start kubelet
Note:
setenforce 0
and sed ...
effectively disables it.
This is required to allow containers to access the host filesystem, which is needed by pod networks for example.
You have to do this until SELinux support is improved in the kubelet.Some users on RHEL/CentOS 7 have reported issues with traffic being routed incorrectly due to iptables being bypassed. You should ensure
net.bridge.bridge-nf-call-iptables
is set to 1 in your sysctl
config, e.g.
cat <<EOF > /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system
Install CNI plugins (required for most pod network):
CNI_VERSION="v0.6.0"
mkdir -p /opt/cni/bin
curl -L "https://github.com/containernetworking/plugins/releases/download/${CNI_VERSION}/cni-plugins-amd64-${CNI_VERSION}.tgz" | tar -C /opt/cni/bin -xz
Install crictl (required for kubeadm / Kubelet Container Runtime Interface (CRI))
CRICTL_VERSION="v1.11.1"
mkdir -p /opt/bin
curl -L "https://github.com/kubernetes-incubator/cri-tools/releases/download/${CRICTL_VERSION}/crictl-${CRICTL_VERSION}-linux-amd64.tar.gz" | tar -C /opt/bin -xz
Install kubeadm
, kubelet
, kubectl
and add a kubelet
systemd service:
RELEASE="$(curl -sSL https://dl.k8s.io/release/stable.txt)"
mkdir -p /opt/bin
cd /opt/bin
curl -L --remote-name-all https://storage.googleapis.com/kubernetes-release/release/${RELEASE}/bin/linux/amd64/{kubeadm,kubelet,kubectl}
chmod +x {kubeadm,kubelet,kubectl}
curl -sSL "https://raw.githubusercontent.com/kubernetes/kubernetes/${RELEASE}/build/debs/kubelet.service" | sed "s:/usr/bin:/opt/bin:g" > /etc/systemd/system/kubelet.service
mkdir -p /etc/systemd/system/kubelet.service.d
curl -sSL "https://raw.githubusercontent.com/kubernetes/kubernetes/${RELEASE}/build/debs/10-kubeadm.conf" | sed "s:/usr/bin:/opt/bin:g" > /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
Enable and start kubelet
:
systemctl enable kubelet && systemctl start kubelet
The kubelet is now restarting every few seconds, as it waits in a crashloop for kubeadm to tell it what to do.
When using Docker, kubeadm will automatically detect the cgroup driver for the kubelet
and set it in the /var/lib/kubelet/kubeadm-flags.env
file during runtime.
If you are using a different CRI, you have to modify the file
/etc/default/kubelet
with your cgroup-driver
value, like so:
KUBELET_EXTRA_ARGS=--cgroup-driver=<value>
This file will be used by kubeadm init
and kubeadm join
to source extra
user defined arguments for the kubelet.
Please mind, that you only have to do that if the cgroup driver of your CRI
is not cgroupfs
, because that is the default value in the kubelet already.
Restarting the kubelet is required:
systemctl daemon-reload
systemctl restart kubelet
If you are running into difficulties with kubeadm, please consult our troubleshooting docs.
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