Understanding what host means in Docker - docker

I was just trying to experiment around with some docker commands, particularly the -v command. I see the below command in the documentation for docker.
$ docker run -d -P --name web -v /src/webapp:/opt/webapp training/webapp python app.py
The following explanation is provided:
This will mount the host directory, /src/webapp, into the container at
/opt/webapp.
I fail to understand the initial part , I.E. This will mount the host directory, /src/webapp, , what does host mean in this scenario/context ? can somebody explain ? I am having a real hard time understanding what host mean , can anybody explain ?
The Documentation can be found HERE

"Host" generally means "the physical computer on which you are running Docker" (or other virtualization service).
In your example, -v /src/webapp:/opt/webapp will expose the /src/webapp directory on the computer running Docker inside the web container as the directory /opt/webapp.

Related

Docker Windows Bind Mount not Copying and Refreshing Data

I'm using Docker on Windows. Versions are engine: 20.10.14, desktop: 4.7.0. In my current director, I have a DockerFile (unimportant for now) and an index.html file.
I created an nginx docker container with a bind mount to copy these files into the container: docker container run -d --name nginx_cust -p 80:80 -v %cd%:/usr/share/nginx/html nginx.
When I access localhost:80, I don't see my index.html file reflected, and when I enter the running container with bash docker container exec -it nginx_cust bash and check the mounted directory, it's empty:
Inspecting the container, I see that the bind mount does look correct,
and I don't see anything in the container log about this. Any ideas why this is not working?
After a lot of playing around, I realized that this got fixed when I moved the input files to different directory - one that was less-deeply nested. I strongly suspect there was some long filename constraint being violated silently.

Mounting host directory to container

I am launching a container for my application. But my app needs few config files to login. Files are stored in host directory. How can I mount the host filepath to container?
host directory : /opt/myApp/config
Docker command used currently :
sudo docker run container -d --name myApp-container -p 8090:8080 myApp-image
Please suggest the changes in docker command to achieve this.
You need to use -v/--volume key in such way:
-v <host dir>:<container dir>:ro
In your case it will be:
-v /opt/myApp/config:/opt/myApp/config:ro
You can use this key multiple times. You can also drop :ro part if you want directory to be writable.
See Docker documentation on volumes.

When using docker option --mount the target folder is seen as not absolute, while there is no issue when using -v

I am playing around with docker and ran into an issue when mounting docker volumes with --mount instead of -v. It appears to me that the error popping up is not valid, but probably I am missing a small detail here.
The path to which I want bind the created image in the container is seen as not absolute in the --mount scenario.
I am running Docker on a windows 10 machine
I pulled the jenkins/jenkins:lts image and want to spin up 2 containers that use the same configuration. As said before I use this just to play around with docker, and am exploring how the volume system works.
What i did is create a docker volume that is used to share the configuarion.
docker volume create jenkins_cfg
Then I tried to run 2 containers. The first container started with:
docker run -d -p 8081:8080 --name jenkins2 -v jenkins_cfg:/var/jenkins_home jenkins/jenkins:lts
Which works fine..
The second container started with:
docker run -d -p 8085:8080 --name jenkin5 --mount source=jenkins_cfg,target=var/jenkins_home jenkins/jenkins:lts
This results in the error
"C:\Program Files\Docker\Docker\Resources\bin\docker.exe: Error response from daemon: invalid mount config for type "volume": invalid mount path: 'var/jenkins_home' mount path must be absolute.
See 'C:\Program Files\Docker\Docker\Resources\bin\docker.exe run --help'."
Also /var/jenkins_home is not working properly.
While the -v also asks for the same target folder , i would assume that this folder would also work in the target option of --mount. Probably, I am overlooking something here ...
I figured out that the target folder should be preceeded by //
so the docker command would look like
docker run -d -p 8085:8080 --name jenkin5 --mount source=jenkins_cfg,target=//var/jenkins_home jenkins/jenkins:lts
Still no clue why // has to be added, maybe someone can clarify on that one
Actually mount binds are like mounting a part of physical disk volume to the containers. But volumes are like virtual memory you can't access them independently without containers but bind mounts can be accessed independently
Your mount binds should be an absolute path in your host
Hope this helps your cause

How to debug persistent data volume mount for Docker Odoo container?

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.

How do I start tensorflow docker jupyter notebook

I've installed the tensorflow docker container on an ubuntu machine. The tensorflow docker setup instructions specify:
docker run -it b.gcr.io/tensorflow/tensorflow
This puts me into the docker container terminal, and I can run python and execute the Hello World example. I can also manually run .\run_jupyter.sh to start the jupyter notebook. However, I can't reach the notebook from host.
How do I start the jupyter notebook such that I can use the notebook from the host machine? Ideally I would like to use docker to launch the container and start jupyter in a single command.
For a Linux host Robert Graves answer will work, but for Mac OS X or Windows there is more to be done because docker runs in a virtual machine.
So to begin launch the docker shell (or any shell if you are using Linux) and run the following command to launch a new TensorFlow container:
docker run -p 8888:8888 -p 6006:6006 b.gcr.io/tensorflow/tensorflow ./run_jupyter.sh
Then for Mac OS X and Windows you need to do the following only once:
Open VirtualBox
Click on the docker vm (mine was automatically named "default")
Open the settings by clicking settings
In the network settings open the port forwarding dialog
Click the + symbol to add another port and connect a port from your mac to the VM by filling in the dialog as shown below. In this example I chose port 8810 because I run other notebooks using port 8888.
then open a browser and connect to http://localhost:8810 (or whichever port you set in the host port section
Make your fancy pants machine learning app!
My simple yet efficient workflow:
TL;DR version:
Open Docker Quickstart Terminal. If it is already open, run $ cd
Run this once: $ docker run -it -p 8888:8888 -p 6006:6006 -v /$(pwd)/tensorflow:/notebooks --name tf b.gcr.io/tensorflow/tensorflow
To start every time: $ docker start -i tf
If you are not on windows, you should probably change /$(pwd) to $(pwd)
You will get an empty folder named tensorflow in your home directory for use as a persistent storage of project files such as Ipython Notebooks and datasets.
Explanation:
cd for making sure you are in your home directory.
params:
-it stands for interactive, so you can interact with the container in the terminal environment.
-v host_folder:container_folder enables sharing a folder between the host and the container. The host folder should be inside your home directory. /$(pwd) translates to //c/Users/YOUR_USER_DIR in Windows 10. This folder is seen as notebooks directory in the container which is used by Ipython/Jupyter Notebook.
--name tf assigns the name tf to the container.
-p 8888:8888 -p 6006:6006 mapping ports of container to host, first pair for Jupyter notebook, the second one for Tensorboard
-i stands for interactive
Running TensorFlow on the cloud
After further reading of docker documentation I have a solution that works for me:
docker run -p 8888:8888 -p 6006:6006 b.gcr.io/tensorflow/tensorflow ./run_jupyter.sh
The -p 8888:8888 and -p 6006:6006 expose the container ports to the host on the same port number. If you just use -p 8888, a random port on the host will be assigned.
The ./run_jupyter.sh tells docker what to execute within the container.
With this command, I can use a browser on the host machine to connect to http://localhost:8888/ and access the jupyter notebook.
UPDATE:
After wrestling with docker on windows I switched back to a Ubuntu machine with docker. My notebook was being erased between docker sessions which makes sense after reading more docker documentation. Here is an updated command which also mounts a host directory within the container and starts jupyter pointing to that mounted directory. Now my notebook is saved on the host and will be available next time start up tensorflow.
docker run -p 8888:8888 -p 6006:6006 -v /home/rob/notebook:/notebook b.gcr.io/tensorflow/tensorflow sh -c "jupyter notebook /notebook"
Jupyter now has a ready to run Docker image for TensorFlow:
docker run -d -v $(pwd):/home/jovyan/work -p 8888:8888 jupyter/tensorflow-notebook
These steps worked for me if you are a total docker noob using a windows machine.
Versions: Windows 8.1, docker 1.10.3, tensorflow r0.7
Run Docker Quickstart Terminal
After it is loaded, note the ip address. If you can't find it use this docker-machine ip and make a note. Lets call it 'ip address'. Will look something like this: 192.168.99.104 (I made up this ip address)
Paste this command on the docker terminal:
docker run -p 8888:8888 -p 6006:6006 b.gcr.io/tensorflow/tensorflow.
If you are running this for the first time, it will download and install the image on this light weight vm. Then it should say 'The Jupyter notebook is running at ....' -> This is a good sign!
Open your browser at: <your ip address (see above)>:8888. Eg. 192.168.99.104:8888/
Hopefully you can see your ipython files.
To get this to run under hyper-v. Perform the following steps:
1) Create a docker virtual machine using https://blogs.msdn.microsoft.com/scicoria/2014/10/09/getting-docker-running-on-hyper-v-8-1-2012-r2/ this will get you a working docker container. You can connect to it via the console or via ssh. I'd put at least 8gb of memory since I'm sure this will use a lot of memory.
2) run "ifconfig" to determine the IP address of the Docker VM
3) On the docker shell prompt type:
docker run -p 8888:8888 -p 6006:6006 -it b.gcr.io/tensorflow/tensorflow
4) Connect to the Jupyter Workbench using http:/[ifconfig address]:8888/
To tidy up the things a little bit, I want to give some additional explanations because I also suffered a lot setting up docker with tensorflow. For this I refer to this video which is unfortunately not selfexplanatory in all cases.
I assume you already installed docker. The really interesting general part of the video starts at minute 0:44 where he finally started docker. Until there he only downloads the tensorflow repo into the folder, that he then mounts into the container. You can of course put anything else into the container and access it later in the docker VM.
First he runs the long docker command docker run –dit -v /c/Users/Jay/:/media/disk –p 8000 –p 8888 –p 6006 b.gcr.io/tensorflow/tensorflow. The “run” command starts containers. In this case it starts the container “b.gcr.io/tensorflow/tensorflow”, whose address is provided within the tensorflow docker installation tutorial. The container will be downloaded by docker if not already locally available.
Then he gives two additional kinds of arguments: He mounts a folder of the hostsystem at the given path to the container. DO NOT forget to give the partition in the beginning (eg. "/c/").
Additionally he declares ports being available later from the host machine with the params -p.
From all this command you get back the [CONTAINER_ID] of this container execution!
You can always see the currently running containers by running “docker ps” in the docker console. Your container created above should appear in this list with the same id.
Next Step: With your container running, you now want to execute something in it. In our case jupyter notebook or tensorflow or whatever: To do this you make docker execute the bash on the newly created container: docker exec –ti [CONTAINER_ID] bash. This command now starts a bash shell on your container. You see this because the “$” now changed to root#[CONTAINER_ID]:. From here is no way back. If you want to get back to the docker terminal, you have to start another fresh docker console like he is doing in minute 1:10. Now with a bash shell running in the container you can do whatever you want and execute Jupiter or tensorflow or whatever. The folder of the host system, you gave in the run command, should be available now under “/media/disk”.
Last step accessing the VM output. It still did not want to work out for me and I could not access my notebook. You still have to find the correct IP and Port to access the launched notebook, tensorboard session or whatever. First find out the main IP by using docker-machine –ls. In this list you get the URL. (If it is your only container it is called default.) You can leave away the port given here. Then from docker ps you get the list of forwarded ports. When there is written 0.0.0.32776->6006/tcp in the list, you can access it from the hostmachine by using the port given in the first place (Awkyard). So in my case the executed tensorboard in the container said “launched on port 6006”. Then from my hostmachine I needed to enter http://192.168.99.100:32776/ to access it.
-> And that’s it! It ran for me like this!
It gives you the terminal prompt:
FOR /f "tokens=*" %i IN ('docker-machine env --shell cmd vdocker') DO %i
docker run -it tensorflow/tensorflow:r0.9-devel
or
FOR /f "tokens=*" %i IN ('docker-machine env --shell cmd vdocker') DO %i
docker run -it b.gcr.io/tensorflow/tensorflow:latest-devel
You should have 'vdocker' or change vdocker to 'default'.
For some reason I ran into one additional problem that I needed to overcome beyond the examples provided, using the --ip flag:
nvidia-docker run --rm \
-p 8888:8888 -p 6006:6006 \
-v `pwd`:/root \
-it tensorflow/tensorflow:latest-devel-gpu-py3 sh -c "jupyter notebook --ip 0.0.0.0 ."
And then I can access via http://localhost:8888 from my machine. In some ways this makes sense; within the container you bind to 0.0.0.0 which represents all available addresses. But whether I need to do this seems to vary (e.g I've started notebooks using jupyter/scipy-notebook without having to do this).
In any case, the above command works for me, might be of use to others.
As an alternative to the official TensorFlow image, you can also use the ML Workspace Docker image. The ML Workspace is an open-source web IDE that combines Jupyter, VS Code, TensorFlow, and many other tools & libraries into one convenient Docker image. Deploying a single workspace instance is as simple as:
docker run -p 8080:8080 mltooling/ml-workspace:latest
All tools are accessible from the same port and integrated into the Jupyter UI. You can find the documentation here.

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