GitLab CI (docker) でCentOSイメージを使う例（GitLab CI入門） ref: http://qiita.com/tnir/items/ff94ba31157f254a9783

file0.yml

before_script:
  - /bin/echo Testing... CentOS 6.6 x MySQL 5.6.17
  - /bin/echo Testing... CentOS 7 latest x MySQL 5.7 latest
variables:
  MYSQL_ROOT_PASSWORD: "1iEkou9luj4Etrie"

test:centos6xmysql56:
  image: centos:6.6
  services:
  - mysql:5.6.17
  script:
  - rpm -q centos-release
  - yum install -y mysql
  - mysql --version
  - mysql -h mysql -u root -p${MYSQL_ROOT_PASSWORD} -e 'SELECT VERSION()'

test:centos7xmysql57:
  image: centos:7
  services:
  - mysql:5.7
  script:
  - rpm -q centos-release
  - yum install -y mysql
  - mysql --version
  - mysql -h mysql -u root -p${MYSQL_ROOT_PASSWORD} -e 'SELECT VERSION()'

file1.txt

  - mysql -h mysql -u root -p${MYSQL_ROOT_PASSWORD} -e 'SELECT VERSION()'

file2.txt

  services:
  - mysql:5.7

file3.txt

variables:
  MYSQL_ROOT_PASSWORD: "1iEkou9luj4Etrie"

file4.txt

$ rpm -q centos-release
centos-release-7-2.1511.el7.centos.2.10.x86_64
$ yum install -y mysql
[...]
$ mysql --version
mysql  Ver 15.1 Distrib 5.5.44-MariaDB, for Linux (x86_64) using readline 5.1
$ mysql -h mysql -u root -p${MYSQL_ROOT_PASSWORD} -e 'SELECT VERSION()'
VERSION()
5.6.29