I am trying to deploy a mongodb cluster on docker swarm mode, all the mongod daemon are in the same overlay network.
I need to configure the mongodb cluster, i am trying to find a command that works like docker run -it ubuntu in docke rswarm mode so i can log in, any ideas?
Or is there any other way to access the overlay network.
SOLUTION:
First ssh to the node that runs the container, then find out the container id using docker ps and simply use docker exec -it $(id) bash to log on to the container.
Related
When I deploy Apache Airflow with docker-compose, and run it via docker-compose run -d, the CLI Container stops automatically, and I have no Chance to exec into it. I am using the standard docker-compose file, I only deletet the profiles: debug option where the cli is defined.
I first run: docker-compose run
Then: docker exec -it airflow-airflow-cli-1 bash
It then says: Container is Not Running.
Why has it stopped and how can I stop this behaviour?
Are you following the steps in the official guide?
Using the following steps from the guide:
Do curl -LfO 'https://airflow.apache.org/docs/apache-airflow/2.5.0/docker-compose.yaml'
In that folder docker compose up airflow-init
docker-compose up
docker exec -it <FOLDER_NAME>-airflow-scheduler-1 /bin/bash
I end up in the scheduler container where you can use the Airflow CLI. (I ran airflow tasks test example_bash_operator runme_0 '2023-01-01' to test)
I'm trying to docker-containerize PostgreSQL server and this container will have many other applications as well. The need is that, PostgreSQL server data should be mapped to the host volume so that when container is stopped, we won't lose the data. Also that, the next time when we start the container, the same directory can be mapped again and postgres can use the old data. Below is the DOCKERFILE. Note that I'm using ubuntu 22.04 on the host.
FROM ubuntu:22.04
ENV DEBIAN_FRONTEND noninteractive
RUN apt install -y postgresql
ENTRYPOINT ["tail", "-f", "/dev/null"]
Docker image is built using the command
docker build -t pg_test .
and the container is run using the command
docker run --name test -v /home/me/data:/var/lib/postgresql/14/main pg_test
'/home/me/data' is the host directory which is empty where I want to map the postgres server data. '/var/lib/postgresql/14/main' is the directory inside the docker container where the postgres is supposed to store the data.
Once the docker container starts, I enter the docker container using the command
docker exec -it test bash
and once I'm inside, I'm trying to start the PostgreSQL service. But PostgreSQL fails to start as there is no data in '/var/lib/postgresql/14/main' directory. I understand that since I have mapped an empty host directory to '/var/lib/postgresql/14/main' directory, postgres doesn't have the files required to start.
I understand that I'm doing it the wrong way, but I couldn't find a way around it. Can anyone please help me to do this the right way, if there is one?
Any help would be appreciable.
You should use the postgres docker image, it will set up the db for you when you start the container, you can find instructions on https://hub.docker.com/_/postgres
If you must use a custom image, you will need to initialize the db yourself, usually by running initdb or whatever your system provides.
But really you should use the appropriate docker image, and if you need more services you start them in their own container and connect them to the postgres one
Currently i created a docker image by using build command in the minikube itself. But i need to know is there any way to copy the docker image in my system docker daemon to minikube docker daemon environment. I don't need to use Dockerhub.
Yes, you can point your terminal to use the docker daemon inside minikube by running this,
$ eval $(minikube docker-env)
Then you can build your own image,
docker build -t my_image .
For more info, see https://minikube.sigs.k8s.io/docs/handbook/pushing/
I am using the mssql docker image (Linux) for sql server 2019. The default user is not root but mssql.
I need to perform some operations as root inside the container:
docker exec -it sql bash
mssql#7f5a78a63728:/$ sudo <command>
bash: sudo: command not found
Then I start the shell as root:
docker exec -it --user=root sql bash
root#7f5a78a63728:/# <command>
...
This works.
Now I need to do this in a container deployed in an AKS cluster
kubectl exec -it rms-sql-1-sql-server-deployment-86cc45dc5c-tgtm2 -- bash
mssql#rms-sql-1-sql-server-host:/$ sudo <command>
bash: sudo: command not found
as expected. But then:
kubectl exec -it --user=root rms-sql-1-sql-server-deployment-86cc45dc5c-tgtm2 -- bash
error: auth info "root" does not exist
So when the container is in an AKS cluster, starting a shell as root doesn't work.
I then try to ssh into the node and use docker from inside:
kubectl debug node/aks-agentpool-30797540-vmss000000 -it --image=mcr.microsoft.com/aks/fundamental/base-ubuntu:v0.0.11
Creating debugging pod node-debugger-aks-agentpool-30797540-vmss000000-xfrsq with container debugger on node aks-agentpool-30797540-vmss000000.
If you don't see a command prompt, try pressing enter.
root#aks-agentpool-30797540-vmss000000:/# docker ...
bash: docker: command not found
Looks like a Kubernetes cluster node doesn't have docker installed!
Any clues?
EDIT
The image I used locally and in Kubernetes is exactly the same,
mcr.microsoft.com/mssql/server:2019-latest untouched
David Maze has well mentioned in the comment:
Any change you make in this environment will be lost as soon as the Kubernetes pod is deleted, including if you need to update the underlying image or if its node goes away outside of your control. Would building a custom image with your changes be a more maintainable solution?
Generally, if you want to change something permanently you have to create a new image. Everything you described behaved exactly as it was supposed to. First you have exec the container in docker, then logged in as root. However, in k8s it is a completely different container. Perhaps a different image is used. Second, even if you made a change, it would exist until the container dies. If you want to modify something permanently, you have to create your new image with all the components and the configuration you need. For more information look at pod lifecycle.
I'm very new to using docker and I've created a postgres container using
docker run --name mytrainingdb -e POSTGRES_PASSWORD=mysecretpassword -d postgres. Then I connected to it with docker exec -it <container-id> bash and then psql.
Then I stop the container.
My query is, what do I do reconnect to the same database? I tried to run same docker run command, but it says the name 'mytrainingdb' is used, which means it is trying to create it afresh, which is not what I want. Hope my expectation is right, as in when I restart my laptop or resume work I can just restart the same container and my data/config would be preserved?
The documentation also mentions that we can link a host directory to volume of pg container to have the stored data accessible to us, but I'm ok with docker managing my storage for that database.
You will have error when you try to re-run the same command, because docker is trying to create a new container with same name as the previous one "mytrainingdb". If you close docker and reopen it you will still find your container , but its not running , you can start it again with docker start mytrainingdb or you can remove it with docker rm mytrainingdb .
However , dont restart docker because you want to create a new container with the same name! If you want to start a new container with the same name and your container is still running you can first stop it with docker stop mytrainingdb and docker rm mytrainingdb or you can just do docker rm -f mytrainingdb (this will remove you running container with force ) and then create a new container..
As for the volumes ,you just created one by default which is named is kind of hash , and its found at volumes/var/lib/docker/volumes/ .Because generally containers such PostgreSQL, or databases in general persists volumes. The volume gets created when running the container and is handy to save persistent data, whether you start the container with -v or not.
The volume you talked about in your question , is called mounted volume , is when you basically just bind a certain directory or file from the host (outside) to inside the container
docker run -v /hostdir:/containerdir in your case docker run -v /hostdir:/var/lib/postgresql/data
If you restart docker or your computer running containers won't be automatically restarted. You can start your container again with docker start mytrainingdb (related question), then connect with your docker exec command.
(one tip: instead of running bash, then psql, you can directly run psql, e.g. docker exec -it mytrainingdb psql --user postgres)
Your understanding of data persistence is correct, docker will manage the data and it will still be around.
From the postgres image documentation
There are several ways to store data used by applications that run in Docker containers. We encourage users of the postgres images to familiarize themselves with the options available, including:
Let Docker manage the storage of your database data by writing the database files to disk on the host system using its own internal volume management. This is the default and is easy and fairly transparent to the user. The downside is that the files may be hard to locate for tools and applications that run directly on the host system, i.e. outside containers.
You can add --rm argument so that whenever you stop the container manually, or container stops for any reasons (his task is done or it fails), it will remove that container.
In your case, you can use this:
docker run --name mytrainingdb --rm -e POSTGRES_PASSWORD=mysecretpassword -d postgres