Services

You cannot memorise a Pod that will be recreated. A Service fixes an address in front of them, keeping callers stable while pods churn. One address in front of many A Deployment gives you multiple, interchangeable pods, and each one has its own IP that will soon be recreated. A Service is the stable home in front of them: you declare a name and a selector, and the platform hands the Service a virtual cluster IP plus a DNS name that stay fixed. Cluster DNS resolves that name, so components (other pods, an Ingress, a load balancer) refer to the Service, never to an individual pod address. That is the point of the abstraction, the address is durable even though everything standing behind it is disposable. ...

Linger changes when an account’s systemd user manager is kept available. With lingering enabled, logind can start that manager at boot and retain it after the account’s login sessions end. This supports unattended work owned by a normal account. The flag controls manager lifetime; individual services still have their own activation, failure, shutdown, and installation rules. ...