How to install/upgrade/downgrade kubectl in Linux (Ubuntu)?

To install the latest version:

curl -LO "https://dl.k8s.io/release/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl"
curl -LO "https://dl.k8s.io/$(curl -L -s https://dl.k8s.io/release/stable.txt)/bin/linux/amd64/kubectl.sha256"
echo "$(<kubectl.sha256) kubectl" | sha256sum --check
sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl
kubectl version --client
kubectl version

To install a specific (v1.19.0) version:

curl -LO "https://dl.k8s.io/release/v1.19.0/bin/linux/amd64/kubectl"
curl -LO "https://dl.k8s.io/v1.19.0/bin/linux/amd64/kubectl.sha256"
echo "$(<kubectl.sha256) kubectl" | sha256sum --check
sudo install -o root -g root -m 0755 kubectl /usr/local/bin/kubectl
kubectl version --client
kubectl version

This will install kubectl client. Run minikube start to install kubectl server.