Run job in GitLab runner only in specific hostname

I want to run one job when a user pushes a commit only if the runner that started the pipeline is running in a specific machine (e.g myciserver).

This is my gitlab-ci.yml:

stages:
  - build

pull-docker-image:
  stage: build
  script:
    - docker pull ubuntu:20.04

So far, I tried to use the keyword only together with variables using the predefined variable $CI_SERVER_NAME:

stages:
  - build

pull-docker-image:
  stage: build
  script:
    - docker pull ubuntu:20.04
  only:
    variables:
      - $CI_SERVER_NAME == "myciserver"

However, the predefined GiLab variable $CI_SERVER_NAME is not the host name of the machine where the job is being executed, instead it always returns the string "GitLab".

How could I accomplish this? Thanks in advance.

Solution

There is the option to tag different runners with labels and you can specify which labels should apply to a runner to be executed.

eg. you label your runner with my-ci your job will look like this

pull-docker-image:
  stage: build
  tags:
    - my-ci
  script:
    - docker pull ubuntu:20.04

but be aware that the job will now only run if there is a runner with those labels available.

Further documentation can be found here: https://docs.gitlab.com/ee/ci/yaml/#tags