Passing Docker container's run parameters in Kubernetes - docker

Question

I have two containers (GitLab and PostgreSQL) running on RancherOS v1.0.3. I would like to make them part of Kubernetes cluster.
[rancher#rancher-agent-1 ~]$ cat postgresql.sh
docker run --name gitlab-postgresql -d \
--env 'POSTGRES_DB=gitlabhq_production' \
--env 'POSTGRES_USER=gitlab' --env 'POSTGRES_PASSWORD=password' \
--volume /srv/docker/gitlab/postgresql:/var/lib/postgresql \
postgres:9.6-2
[rancher#rancher-agent-1 ~]$ cat gitlab.sh
docker run --name gitlab -d \
--link gitlab-postgresql:postgresql \
--publish 443:443 --publish 80:80 \
--env 'GITLAB_PORT=80' --env 'GITLAB_SSH_PORT=10022' \
--env 'GITLAB_SECRETS_DB_KEY_BASE=64-char-key-A' \
--env 'GITLAB_SECRETS_SECRET_KEY_BASE=64-char-key-B' \
--env 'GITLAB_SECRETS_OTP_KEY_BASE=64-char-key-C' \
--volume /srv/docker/gitlab/gitlab:/home/git/data \
sameersbn/gitlab:9.4.5
Queries:
1) I have some idea about how to use YAML files to provision pods, replication controller etc. but i am not sure how to pass the above docker run parameters to Kubernetes so that it can apply the same to image(s) correctly.
2) I'm not sure whether --link argument (used in gitlab.sh above) also need to be passed in Kubernetes. Although i am currently deploying both containers on single host but will be creating cluster of each (PostgreSQL and GitLab) later, so just wanted to confirm whether inter-host communication will automatically be taken care of by Kubernetes. If not, then what options can be explored?

Answer 1

You should first try to represent your run statements into a docker-compose.yml file. Which is quite easy and it would turn something like below
version: '3'
services:
postgresql:
image: postgres:9.6-2
environment:
- "POSTGRES_DB=gitlabhq_production"
- "POSTGRES_USER=gitlab"
- "POSTGRES_PASSWORD=password"
volumes:
- /srv/docker/gitlab/postgresql:/var/lib/postgresql
gitlab:
image: sameersbn/gitlab:9.4.5
ports:
- "443:443"
- "80:80"
environment:
- "GITLAB_PORT=80"
- "GITLAB_SSH_PORT=10022"
- "GITLAB_SECRETS_DB_KEY_BASE=64-char-key-A"
- "GITLAB_SECRETS_SECRET_KEY_BASE=64-char-key-B"
- "GITLAB_SECRETS_OTP_KEY_BASE=64-char-key-C"
volumes:
- /srv/docker/gitlab/gitlab:/home/git/data
Now there is a amazing tool name kompose from kompose.io which does the conversion part for you. If you convert the above you will get the related files
$ kompose convert -f docker-compose.yml
WARN Volume mount on the host "/srv/docker/gitlab/gitlab" isn't supported - ignoring path on the host
WARN Volume mount on the host "/srv/docker/gitlab/postgresql" isn't supported - ignoring path on the host
INFO Kubernetes file "gitlab-service.yaml" created
INFO Kubernetes file "postgresql-service.yaml" created
INFO Kubernetes file "gitlab-deployment.yaml" created
INFO Kubernetes file "gitlab-claim0-persistentvolumeclaim.yaml" created
INFO Kubernetes file "postgresql-deployment.yaml" created
INFO Kubernetes file "postgresql-claim0-persistentvolumeclaim.yaml" created
Now you have to fix the volume mount part as per kubernetes. This completes 80% of the work and you just need figure out the rest 20%
Here is a cat of all the generate files, so that you can just see what kind of files are generated
==> gitlab-claim0-persistentvolumeclaim.yaml <==
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
creationTimestamp: null
labels:
io.kompose.service: gitlab-claim0
name: gitlab-claim0
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 100Mi
status: {}
==> gitlab-deployment.yaml <==
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
creationTimestamp: null
labels:
io.kompose.service: gitlab
name: gitlab
spec:
replicas: 1
strategy:
type: Recreate
template:
metadata:
creationTimestamp: null
labels:
io.kompose.service: gitlab
spec:
containers:
- env:
- name: GITLAB_PORT
value: "80"
- name: GITLAB_SECRETS_DB_KEY_BASE
value: 64-char-key-A
- name: GITLAB_SECRETS_OTP_KEY_BASE
value: 64-char-key-C
- name: GITLAB_SECRETS_SECRET_KEY_BASE
value: 64-char-key-B
- name: GITLAB_SSH_PORT
value: "10022"
image: sameersbn/gitlab:9.4.5
name: gitlab
ports:
- containerPort: 443
- containerPort: 80
resources: {}
volumeMounts:
- mountPath: /home/git/data
name: gitlab-claim0
restartPolicy: Always
volumes:
- name: gitlab-claim0
persistentVolumeClaim:
claimName: gitlab-claim0
status: {}
==> gitlab-service.yaml <==
apiVersion: v1
kind: Service
metadata:
creationTimestamp: null
labels:
io.kompose.service: gitlab
name: gitlab
spec:
ports:
- name: "443"
port: 443
targetPort: 443
- name: "80"
port: 80
targetPort: 80
selector:
io.kompose.service: gitlab
status:
loadBalancer: {}
==> postgresql-claim0-persistentvolumeclaim.yaml <==
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
creationTimestamp: null
labels:
io.kompose.service: postgresql-claim0
name: postgresql-claim0
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 100Mi
status: {}
==> postgresql-deployment.yaml <==
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
creationTimestamp: null
labels:
io.kompose.service: postgresql
name: postgresql
spec:
replicas: 1
strategy:
type: Recreate
template:
metadata:
creationTimestamp: null
labels:
io.kompose.service: postgresql
spec:
containers:
- env:
- name: POSTGRES_DB
value: gitlabhq_production
- name: POSTGRES_PASSWORD
value: password
- name: POSTGRES_USER
value: gitlab
image: postgres:9.6-2
name: postgresql
resources: {}
volumeMounts:
- mountPath: /var/lib/postgresql
name: postgresql-claim0
restartPolicy: Always
volumes:
- name: postgresql-claim0
persistentVolumeClaim:
claimName: postgresql-claim0
status: {}
==> postgresql-service.yaml <==
apiVersion: v1
kind: Service
metadata:
creationTimestamp: null
labels:
io.kompose.service: postgresql
name: postgresql
spec:
clusterIP: None
ports:
- name: headless
port: 55555
targetPort: 0
selector:
io.kompose.service: postgresql
status:
loadBalancer: {}