Install PowerShell in Debian 9

To install Microsoft PowerShell in Debian 9, run

apt-get update
apt-get install curl gnupg apt-transport-https

Install GPG keys

curl https://packages.microsoft.com/keys/microsoft.asc | apt-key add -

Add repository

echo "deb [arch=amd64] https://packages.microsoft.com/repos/microsoft-debian-stretch-prod stretch main" > /etc/apt/sources.list.d/microsoft.list

Install powershell

apt-get update && apt-get install -y powershell

To start powershell, run

pwsh