GitLab CI/CD Pipeline Configuration Reference：三 [Parameter details: script before_script and after_script stage]

job:
  script: "bundle exec rspec"

YAML anchors for script

Introduced in GitLab 12.5.

You can use YAML anchors with scripts, which makes it possible to
include a predefined list of commands in multiple jobs.
For example:

.something: &something
- echo ‘something‘

job_name:
  script:
    - *something
    - echo ‘this is the script‘

YAML anchors for variables
YAML anchors can be used with variables, to easily repeat assignment of variables across multiple jobs. It can also enable more flexibility when a job requires a specific variables 
block that would otherwise override the global variables.

In the example below, we will override the GIT_STRATEGY variable without affecting the use of the SAMPLE_VARIABLE variable:
# global variables
variables: &global-variables
  SAMPLE_VARIABLE: sample_variable_value

# a job that needs to set the GIT_STRATEGY variable, yet depend on global variables
job_no_git_strategy:
  stage: cleanup
  variables:
    <<: *global-variables
    GIT_STRATEGY: none
  script: echo $SAMPLE_VARIABLE

Hide jobs

Introduced in GitLab 8.6 and GitLab Runner v1.1.1.

If you want to temporarily ‘disable‘ a job, rather than commenting out all the
lines where the job is defined:
#hidden_job:
#  script:
#    - run test
you can instead start its name with a dot (.) and it won‘t be processed by
GitLab CI/CD. In the following example, .hidden_job will be ignored:
.hidden_job:
  script:
    - run test
Use this feature to ignore jobs, or use the
special YAML features and transform the hidden jobs
into templates.

Skip Pipeline
If your commit message contains [ci skip] or [skip ci], using any
capitalization, the commit will be created but the pipeline will be skipped.
Alternatively, one can pass the ci.skip Git push option
if using Git 2.10 or newer.

job:
  script:
    - uname -a
    - bundle exec rspec

job:
  script:
    - false || exit_code=$?
    - if [ $exit_code -ne 0 ]; then echo "Previous command failed"; fi;

default:
  before_script:
    - global before script

job:
  before_script:
    - execute this instead of global before script
  script:
    - my command
  after_script:
    - execute this after my script

stages:
  - build
  - test
  - deploy

job 0:
  stage: .pre
  script: make something useful before build stage

job 1:
  stage: build
  script: make build dependencies

job 2:
  stage: build
  script: make build artifacts

job 3:
  stage: test
  script: make test

job 4:
  stage: deploy
  script: make deploy

job 5:
  stage: .post
  script: make something useful at the end of pipeline

###

.pre and .post

Introduced in GitLab 12.4.

The following stages are available to every pipeline:

• .pre, which is guaranteed to always be the first stage in a pipeline.
• .post, which is guaranteed to always be the last stage in a pipeline.

User-defined stages are executed after .pre and before .post.

The order of .pre and .post can‘t be changed, even if defined out of order in .gitlab-ci.yml. For example, the following are equivalent configuration:

• Configured in order:

  stages:
    - .pre
    - a
    - b
    - .post

• Configured out of order:

  stages:
    - a
    - .pre
    - b
    - .post

• Not explicitly configured:

  stages:
    - a
    - b

NOTE: Note: A pipeline won‘t be created if it only contains jobs in .pre or .post stages.

[root@worker01 ~]# docker exec -it gitlab-runner cat /etc/gitlab-runner/config.toml
concurrent = 1
check_interval = 0

[session_server]
  session_timeout = 1800

[[runners]]
  name = "opstest"
  url = "http://10.197.236.131:9800/"
  token = "F_b9oZ1Riijo_W4TqxfA"
  executor = "shell"
  [runners.custom_build_dir]
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]

Advanced configuration

GitLab Runner configuration uses the TOML format.

The file to be edited can be found in:

    /etc/gitlab-runner/config.toml on *nix systems when GitLab Runner is executed as root (this is also path for service configuration)   ## root用户使用的config.toml
    ~/.gitlab-runner/config.toml on *nix systems when GitLab Runner is executed as non-root  ## 非root用户使用的config.toml
    ./config.toml on other systems  ## 其它

The global section

This defines global settings of GitLab Runner.
Setting        Description
concurrent     limits how many jobs globally can be run concurrently. The most upper limit of jobs using all defined runners. 0 does not mean unlimited
log_level      Log level (options: debug, info, warn, error, fatal, panic). Note that this setting has lower priority than level set by command line argument --debug, -l, or --log-level
log_format     Log format (options: runner, text, json). Note that this setting has lower priority than format set by command line argument --log-format The default value is runner.
check_interval     defines the interval length, in seconds, between new jobs check. The default value is 3; if set to 0 or lower, the default value will be used.
sentry_dsn     enable tracking of all system level errors to Sentry
listen_address     address (<host>:<port>) on which the Prometheus metrics HTTP server should be listening

Configuration example:

concurrent = 4
log_level = "warning"

log_format examples (truncated)

runner

Runtime platform                                    arch=amd64 os=darwin pid=37300 revision=HEAD version=development version
Starting multi-runner from /etc/gitlab-runner/config.toml...  builds=0
WARNING: Running in user-mode.
WARNING: Use sudo for system-mode:
WARNING: $ sudo gitlab-runner...

Configuration loaded                                builds=0
listen_address not defined, metrics & debug endpoints disabled  builds=0
[session_server].listen_address not defined, session endpoints disabled  builds=0

text

INFO[0000] Runtime platform                              arch=amd64 os=darwin pid=37773 revision=HEAD version="development version"
INFO[0000] Starting multi-runner from /etc/gitlab-runner/config.toml...  builds=0
WARN[0000] Running in user-mode.
WARN[0000] Use sudo for system-mode:
WARN[0000] $ sudo gitlab-runner...
INFO[0000]
INFO[0000] Configuration loaded                          builds=0
INFO[0000] listen_address not defined, metrics & debug endpoints disabled  builds=0
INFO[0000] [session_server].listen_address not defined, session endpoints disabled  builds=0

json

{"arch":"amd64","level":"info","msg":"Runtime platform","os":"darwin","pid":38229,"revision":"HEAD","time":"2020-06-05T15:57:35+02:00","version":"development version"}
{"builds":0,"level":"info","msg":"Starting multi-runner from /etc/gitlab-runner/config.toml...","time":"2020-06-05T15:57:35+02:00"}
{"level":"warning","msg":"Running in user-mode.","time":"2020-06-05T15:57:35+02:00"}
{"level":"warning","msg":"Use sudo for system-mode:","time":"2020-06-05T15:57:35+02:00"}
{"level":"warning","msg":"$ sudo gitlab-runner...","time":"2020-06-05T15:57:35+02:00"}
{"level":"info","msg":"","time":"2020-06-05T15:57:35+02:00"}
{"builds":0,"level":"info","msg":"Configuration loaded","time":"2020-06-05T15:57:35+02:00"}
{"builds":0,"level":"info","msg":"listen_address not defined, metrics \u0026 debug endpoints disabled","time":"2020-06-05T15:57:35+02:00"}
{"builds":0,"level":"info","msg":"[session_server].listen_address not defined, session endpoints disabled","time":"2020-06-05T15:57:35+02:00"}