Log into your private registry manually from the shell:
docker login registry.research.example.com:5000 --username my_username --password my_password
# ex:
docker login https://registry.research.example.com --username abcd --password password
then grab this file:
cat ~/.docker/config.json
# the entire JSON string, and add it in Gitlab under your Group -> Settings -> CI/CD -> Variables, and add new variable:
# Key: DOCKER_AUTH_CONFIG
# Value: the JSON string from above.
Ex:
{
"auths": {
"registry.research.example.com": {
"auth": "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX="
}
},
"HttpHeaders": {
"User-Agent": "Docker-Client/19.03.1 (linux)"
}
}