block16.bash

$ kubectl rollout undo deployment/gs-spring-boot-docker-deployment --to-revision=2
deployment "gs-spring-boot-docker-deployment" rolled back

# 기존 Running Pod이 Terminating 되고, 신규 생성된 Pod이 Running 되었습니다.
$ kubectl get pod
NAME                                                READY     STATUS        RESTARTS   AGE
gs-spring-boot-docker-deployment-56fb494f67-g2lwr   1/1       Terminating   0          5h
gs-spring-boot-docker-deployment-56fb494f67-rfvnv   1/1       Terminating   0          6m
gs-spring-boot-docker-deployment-7fbf88754d-6grl7   1/1       Terminating   0          1h
gs-spring-boot-docker-deployment-7fbf88754d-7zx7s   1/1       Running       0          6s

# Revision #2에 해당하는 Replica Sets를 유지키시고 있었기 때문에, 새로 Replica Sets을 생성하지 않고 Rollback이 수행 됨을 알 수 있습니다.
$ kubectl get rs
NAME                                          DESIRED   CURRENT   READY     AGE
gs-spring-boot-docker-deployment-56fb494f67   0         0         0         5h
gs-spring-boot-docker-deployment-7fbf88754d   1         1         1         1h