Write command args in kubernetes deployment

Question

Can anyone help with this, please?

I have a mongo pod assigned with its service. I need to execute some commands while starting the container in the pod.

I found a small examples like this:

command: ["printenv"]
    args: ["HOSTNAME", "KUBERNETES_PORT"]

But I want to execute these commands while starting the pod:

use ParkInDB
db.roles.insertMany( [ {name :"ROLE_USER"}, {name:"ROLE_MODERATOR"}, {name:"ROLE_ADMIN"} ])

Do you want to run those commands every time the pod (re)starts, even if it gets moved between nodes? Do you want to run those commands instead of the main mongod process, or after it's already started up? A separate Job might be easier to manage. — David Maze, Dec 05 '20 at 02:57
hello thank you for your answer , i want to run these commands , everytime the pod restarts and no i don't want it instead of the main mongodb process , i want them when its already started up — benhsouna chaima, Dec 05 '20 at 10:52

score 1 · Answer 1 · answered Dec 07 '20 at 12:10

you need to choice one solution :

1- use init-container to deployment for change and execute some command or file

2- use command and args in deployment yaml

for init-container visit this page and use.

for comnad and args use this model in your deployment yaml file:

- image:
  name:
  command: ["/bin/sh"]
  args: ["-c" , "PUT_YOUR_COMMAND_HERE"]

score 0 · Answer 2 · answered Dec 04 '20 at 18:23

0

if you are looking forward to run the command before the container start or container stop you can use the container life cycle hooks.

https://kubernetes.io/docs/concepts/containers/container-lifecycle-hooks/

however, if you can add a command in the shell script file and edit MongoDB image as per requirement

command:  ["/bin/sh", "-c", "/usr/src/script.sh"]

you also edit the yaml with

args:
  - '-c'
  - |
    ls
    rm -rf sql_scripts

answered Dec 04 '20 at 18:23

Harsh Manvar

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i want to execute these command in mongo mode when the container is first launched in the pod because the backend cannot interact with the mongo unless the db is created and roles collections are created two – benhsouna chaima Dec 05 '20 at 11:23

score 0 · Answer 3 · edited Jul 13 '21 at 09:46

When you use the official Mongo image, you can specify scripts to use on container startup. The answer accepted here provides you with some information on how this work.

Kubernetes

When it comes to Kubernetes, there are some pre-work you need to do.

What you can do is to write a script like my-script.sh that creates a userDB and insert an item into the users collection:

mongo userDB --eval 'db.users.insertOne({username: "admin", password: "12345"})'

and then write a Dockerfile based on the official mongo image, to copy your script into the folder where custom scripts are run on database initialization.

FROM mongo:latest

COPY my-script.sh /docker-entrypoint-initdb.d/

CMD ["mongod"]

Within the same directory containing your script and dockerfile, build the docker image with

docker build -t dockerhub-username/custom-mongo .

Push the image to docker hub or any repository of your choice, and use it in your deployment yaml.

deployment.yaml

...
spec:
  containers:
    - name: mongodb-standalone
      image: dockerhub-username/custom-mongo
      ports:
        - containerPort: 27017

Verify by going to your pod and check the logs. You will be able to see that mongo has initialized the db that you have specified in your script in the directory /docker-entrypoint-initdb.d/.

Write command args in kubernetes deployment

3 Answers3

Kubernetes

deployment.yaml