Gitlab Pipeline Remote SSH To Server Staging Auto Deploy & Production Manual Deploy

.gitlab-ci.yaml

#Pipeline Created by Taufiq - 2022
image: alpine:latest
stages:
  - build-server-stg
  - deploy-server-stg
  - build-server-prd
  - deploy-server-prd

################################################
#Staging pipeline configuration : Auto Deployment
################################################

build-server-stg:
  stage: build-server-stg
  before_script:  
  - 'which ssh-agent || ( apk update && apk add openssh )'
  - mkdir -p ~/.ssh
  - eval $(ssh-agent -s)
  - '[[ -f /.dockerenv ]] && echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config'
  script:
    - ssh-add <(echo "$SECRET_KEY_base64_STAGING" | base64 -d)
    - ssh -o StrictHostKeyChecking=no $SSH_USER_STAGING@$SSH_HOST_STAGING -p $SSH_PORT_STAGING "linux_command_here"
  only:
    refs:
    - staging #Run only for branches
    changes:
    - "server/**/*" #Run only changes folder in repository for triggering pipeline

deploy-server-stg:
  stage: deploy-server-stg
  before_script:  
  - 'which ssh-agent || ( apk update && apk add openssh )'
  - mkdir -p ~/.ssh
  - eval $(ssh-agent -s)
  - '[[ -f /.dockerenv ]] && echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config'
  script:
    - ssh-add <(echo "$SECRET_KEY_base64_STAGING" | base64 -d)
    - ssh -o StrictHostKeyChecking=no $SSH_USER_STAGING@$SSH_HOST_STAGING -p $SSH_PORT_STAGING "linux_command_here"
  only:
    refs:
    - staging
    changes:
    - "server/**/*" #Define changes in repository for triggering pipeline

################################################
#Production pipeline configuration: Manual Deployment
################################################

build-server-prd:
    stage: build-server-prd
    before_script:  
    - 'which ssh-agent || ( apk update && apk add openssh )'
    - mkdir -p ~/.ssh
    - eval $(ssh-agent -s)
    - '[[ -f /.dockerenv ]] && echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config'
    script:
      - ssh-add <(echo "$SECRET_KEY_base64_PRODUCTION" | base64 -d)
      - ssh -o StrictHostKeyChecking=no $SSH_USER_STAGING@$SSH_HOST_PRODUCTION -p $SSH_PORT_PRODCUTION "linux_command_here"
    only:
      refs:
      - main #Run only for branches
      changes:
      - "server/**/*" #Define changes in repository for triggering pipeline
  
deploy-server-prd:
  stage: deploy-server-prd
  before_script:  
  - 'which ssh-agent || ( apk update && apk add openssh )'
  - mkdir -p ~/.ssh
  - eval $(ssh-agent -s)
  - '[[ -f /.dockerenv ]] && echo -e "Host *\n\tStrictHostKeyChecking no\n\n" > ~/.ssh/config'
  script:
    - ssh-add <(echo "$SECRET_KEY_base64_PRODUCTION" | base64 -d)
    - ssh -o StrictHostKeyChecking=no $SSH_USER_PRODUCTION@$SSH_HOST_STAGING -p $SSH_PORT_PRODUCTION "linux_command_here"
  only:
    refs:
    - main #Run only for branches
    changes:
    - "server/**/*" #Define changes in repository for triggering pipeline
  when: manual #Deploy manually

README

##Setup the variable on gitlab 
$SECRET_KEY_base64
$SSH_USER*
$SSH_HOST*
$SSH_PORT*

Notes: Checklist protected variable for running pipeline only on it and configure the protected branch in 
       Repository > Settings > General > Protected Branhces

##Generate the secret key
ssh-keygen -t rsa

###Add public key to authorized_keys
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys 

###Encode private key with base64 encoding
cat ~/.ssh/id_rsa | base64

Early I used ubuntu:latest for the base image but its slow, I suggest to use alpine:latest instead

ubuntu:latest 00:03:38
alpine:latest 00:02:14