I'm running a docker container of a db/2 luw image (custom image of a DB2ExpressC on RHEL). The container exposes the service to port 50000 and is available from the "outside". The user is db2inst1 and seems to be a standard username for the database.
I start the container with the following command:
docker run --rm -itd -e DB2INST1_PASSWORD=kvl -e DBNAME=BLA -p 50000:50000 -v db2luw:/home/db2inst1 db2:v11.1-7
When i look into the container there is a home-directory of the db2inst1 user wherein the db-instance places its data. I thought if i create a volume with the home-directory as mountpoint, it would cause my data to be persistet in it after a restart of the container.
Has anyone an idea what the problem could be? I cant find a wiki or useful documentation.
The solution was to create the volume with the correct target (mount-point). The db2-image uses
/home/db2inst1/data
as its data-directory.
Related
please bear in mind this is my first time posting here I might not know all the rules and stuff.
so I have just started working with dockers and images. I created a small .Net app and I used MsSQLServer docker image in my app. The app gets connected with the server and I am able to create database using CodeFirst approach (add-migration and update database works fine).
i am running my SQL container with -rm mode. Although it has a volume mounted to it but i have to create database every time i rerun the container.
I read that if we want our data not to get lost when we delete the container we have to mount volumes to our container. i had done the same thing using MongoDb docker image and it worked fine. my data is still present even when i stop and rerun my MongoContainer. but my MSSQL is unable to retain data.
here is the command i m using to run my docker image ( i know about docker-compose but i am avoiding using it for now)
docker run -d --rm --name mssqlserver -p 1433:1433 -e "ACCEPT_EULA=Y" -e MSSQL_SA_PASSWORD=********** -v sqlData:/data/db mcr.microsoft.com/mssql/server
Note: this says it will not delete named volume with --rm
https://docs.docker.com/engine/reference/run/#clean-up---rm
The path you mount the volume on is a Linux path, so you need to use forward slashes rather than back-slashes, like this
docker run -d --rm --name mssqlserver -p 1433:1433 -e "ACCEPT_EULA=Y" -e MSSQL_SA_PASSWORD=********** -v sqlData:/var/opt/mssql mcr.microsoft.com/mssql/server
Whenever I am using
docker run -i -t ae8c587afa40 /bin/bash command
it always creates a new container with a new ID. Can someone help me on how to save that particular container so that whenever I exit from that container my data doesn't get lost?
You can run the container in background by using the below option:
docker run -d --hostname=quickstart.cloudera --privileged=true -t -i -p 7180:7180 -p 8888:8888 -p 10000:10000 -p 8020:8020 -p 9092:9092 -p 9093:9093 -p 9393:9393 -p 9394:9394 -p 24042:24042 4239cd2958c6 /usr/bin/docker-quickstart
The -d option will help to run the container even if you exit from the terminal on which container was started. New container id will be created. The id present in the docker run command is the image id.
Can someone help me on how to save that particular container so that whenever I exit from that container my data doesn't get lost?
You should not rely on containers re usability. Instead of executing manually commands inside a container, build your own custom image including these commands. By doing this, you do not need to worry about starting a specific container cause all containers of that image will include the commands that you have defined when building the image.
Another advantage is that you can easily share your image via its Dockerfile or by pushing it to a repository.
I suggest that you read the docs to understand docker's concept.
A docker container goes into the stopped state when you exit from the container.
You can view all docker containers (running and stopped) by using docker ps -a.
In this listing you will see your old container.
If you need to restart it you can do this:
docker start -i <container_id>
This will restart the stopped container.
See - https://docs.docker.com/engine/reference/commandline/start/ for further details on the docker start command.
Note: Having data inside a docker container is not a good idea. You should use volumes or bind mounts to save your data. A good idea is to treat containers as being ephemeral and immutable.
Edit:
To Detach from a container without exiting the shell/process running in the container use the Key sequence Control + P Control + Q.
See https://docs.docker.com/engine/reference/commandline/attach/
I followed the standard Odoo container instructions on Docker to start the required postgres and odoo servers, and tried to pass host directories as persistent data storage for both as indicated in those instructions:
sudo mkdir /tmp/postgres /tmp/odoo
sudo docker run -d -v /tmp/postgres:/var/lib/postgresql/data/pgdata -e POSTGRES_USER=odoo -e POSTGRES_PASSWORD=odoo -e POSTGRES_DB=postgres --name db postgres:10
sudo docker run -v /tmp/odoo:/var/lib/odoo -p 8069:8069 --name odoo --link db:db -t odoo
The Odoo container shows messages that it starts up fine, but when I point my web browser at http://localhost:8069 I get no response from the server. By contrast, if I omit the -v argument from the Odoo docker run command, my web browser connects to the Odoo server fine, and everything works great.
I searched and see other people also struggling with getting the details of persistent data volumes working, e.g. Odoo development on Docker, Encountered errors while bringing up the project
This seems like a significant gap in Docker's standard use-case that users need better info on how to debug:
How to debug why the host volume mounting doesn't work for the odoo container, whereas it clearly does work for the postgres container? I'm not getting any insight from the log messages.
In particular, how to debug whether the container requires the host data volume to be pre-configured in some specific way, in order to work? For example, the fact that I can get the container to work without the -v option seems like it ought to be helpful, but also rather opaque. How can I use that success to inspect what those requirements actually are?
Docker is supposed to help you get a useful service running without needing to know the guts of its internals, e.g. how to set up its internal data directory. Mounting a persistent data volume from the host is a key part of that, e.g. so that users can snapshot, backup and restore their data using tools they already know.
I figured out some good debugging methods that both solved this problem and seem generally useful for figuring out Docker persistent data volume issues.
Test 1: can the container work with an empty Docker volume?
This is a really easy test: just create a new Docker volume and pass that in your -v argument (instead of a host directory absolute path):
sudo docker volume create hello
sudo docker run -v hello:/var/lib/odoo -p 8069:8069 --name odoo --link db:db -t odoo
The odoo container immediately worked successfully this way (i.e. my web browswer was able to connect to the Odoo server). This showed that it could work fine with an (initially) empty data directory. The obvious question then is why it didn't work with an empty host-directory volume. I had read that Docker containers can be persnickety about UID/GID ownership, so my next question was how do I figure out what it expects.
Test 2: inspect the running container's file system
I used docker exec to get an interactive bash shell in the running container:
sudo docker exec -ti odoo bash
Inside this shell I then looked at the data directory ownership, to get numeric UID and GID values:
ls -dn /var/lib/odoo
This showed me the UID/GID values were 101:101. (You can exit from this shell by just typing Control-D)
Test 3: re-run container with matching host-directory UID:GID
I then changed the ownership of my host directory to 101:101 and re-ran the odoo container with my host-directory mount:
sudo chown 101:101 /tmp/odoo
sudo docker stop odoo
sudo docker rm odoo
sudo docker run -v /tmp/odoo:/var/lib/odoo -p 8069:8069 --name odoo --link db:db -t odoo
Success! Finally the odoo container worked properly with a host-directory mount. While it's annoying the Odoo docker docs don't mention anything about this, it's easy to debug if you know how to use these basic tests.
To start I built a docker container from the MariaDB docker image.
After that I loaded a database dumpfile in the running container.
[MariaDB status][1]
Everything goes fine.
When I want to run/link the Drupal image:
docker run --name drupaldocker --link mariadbdocker:mariadb -p 8089:80 -d drupal
I can reach the drupal installation page, but when I want to load the database I always have the same errors:
-host, pass or dbname is wrong.
But I'm pretty sure my credentials are right.
It seems that my drupal container can't find the mariadb image.
Docker links is a deprecated feature and should be avoided: https://docs.docker.com/engine/userguide/networking/default_network/dockerlinks/
I assume you have a container named mariadbdocker running.
If you gain bash access inside drupaldocker container, you should be able to ping mariadb alias like this:
docker run --name drupaldocker --link mariadbdocker:mariadb -p 8089:80 -it drupal /bin/bash
If ping succeeds then you probably still have credentials issue.
For logging purposes I want to know the name of the Docker instance that my program is running under.
For example if I start it as:
docker run -d --name my-docker-name some/image
how can i find the actual docker name (my-docker-name, in this example) from a program running in it?
TL;DR: --hostname option.
Issue
Container's program cannot access its container's name.
Solution a) -dirty and not easy-
https://stackoverflow.com/a/36068029/5321002
Solution b)
Add the option -h|--hostname="" matching the same name as the docker container name. Then you just need to query the hostname from the program and you're done.
edit
Solution c)
Provide, as you suggested, a env-variable with the name. The overall command would look like as follow:
$name="custom-uniq-name"
$docker run -h $name --name $name -e NAME=$name image-to-run
if you add
-v /var/run/docker.sock:/var/run/docker.sock
to your
docker run
command, you expose docker socket to the container, and you will be able to launch docker commands, such as
docker ps --filter
Keep in mind that this is potentially dangerous, now your container has a privileged access to the host.