How to run a specific job in gitlab CI

Simply add a when: manual to the jobs you don't want to run.

These jobs will still appear in your pipeline but won't be run, unless someone "manually" starts them through the web interface, hence the name.

Here's more info about this: https://docs.gitlab.com/ce/ci/yaml/README.html#when

If you're looking for something more "programmable", let's say run either job1 or job2 depending on a branch name or a tag, then you should have a look at the only and except keywords: https://docs.gitlab.com/ce/ci/yaml/README.html#only-and-except

You can use a gitlab variable expression with only/except like below and then pass the variable into the pipeline execution as needed.

This example defaults to running both jobs, but if passed 'true' for "firstJobOnly" it only runs the first job.

Old Approach -- (still valid as of gitlab 13.8) - only/except

variables:
  firstJobOnly: 'false'

before_script:
  - docker info

job1:
  script:
    - do something

job2:
  script:
    - do something
  except:
    variables:
      - $firstJobOnly =~ /true/i

Updated Approach - rules

While the above still works, the best way to accomplish this now would be using the rules syntax. A simple example similar to my original reply is below.

If you explore the options in the rules syntax, depending on the specific project constraints there are many ways this could be achieved.

variables:
  firstJobOnly: 'false'

job1:
  script: 
    - do something

job2:
  script: 
    - do something
  rules:
    - if: '$firstJobOnly == "true"'
      when: never
    - when: always

We faced the same problem in the past and I'm sharing with you our solution.

#Remark#

• I read the answer of Jawad and I found it good and we have tried it when we faced the issue.
• My remark is that adding when: manual will always show ALL your jobs in the pipeline.
• So if you work in a large team, you can't prevent other collaborators to click by error or by mistake on the job you don't want to be launched.

#What I'm supposing before continuing#

• Let's say that you have 4 jobs.
• You need to always run (manually or automatically) job 1, job 2 and job 4 but NOT job3.
• You want to only run job 3 in a specific case or just when you decide to run it.

#The idea is#

• We launch the 3rd job only for tags which match a regular expression.

• In the example below, it's launched for tags like helloTag.1, helloTag.2, helloTag.3... etc.

• If we are in develop or master (or other branch), we will have 3 stages (stage 1, stage 2, stage 4)

  Note how the 3rd job is not present in the pipeline

  

• Go to "Repository" --> "Tags" --> "New tag"

  Give the tag a name which much your regular expression

  

• If we are in a tag having a name which starts with "helloTag.", we will have 1 stage (stage 3)

  Note how other stages are not present here

  

#Example of .gitlab-ci file#

stages:
    - myStage1
    - myStage2
    - myStage3
    - myStage4

This is my first stage:
    stage: myStage1
    before_script:
        - echo "my stage 1 before script"
    script:
         - echo "my stage 1 script"
    except:
        - /^helloTag.*$/

This is my second stage:
    stage: myStage2
    before_script:
        - echo "my stage 2 before script"
    script:
         - echo "my stage 2 script"
    except:
        - /^helloTag.*$/

This is my third stage:
    stage: myStage3
    before_script:
        - echo "my stage 3 before script"
    script:
         - echo "my stage 3 script"
    only:
        - /^helloTag.*$/

This is my fourth stage:
    stage: myStage4
    before_script:
        - echo "my stage 4 before script"
    script:
         - echo "my stage 4 script"
    except:
        - /^helloTag.*$/

Hope that this helps you.