I have a Docker container within a Tomcat server. I would like to access to the conf files of the server from the host.
In this way, i tried to run my container with these options :
docker run -v /home/empty_dir:/usr/local/tomcat/conf test
The /conf directory is well created on the host but is empty and thus the server cannot start...
So, I'm looking for a solution to populate my dir with the default conf file of the server in the container.
Related
I am using Docker to run four containers to run a backend web application. The backend web application uses buildout to assemble the software.
However, the frontend, which is installed and runs on the host machine (that is, not using Docker), needs to access the buildout directory inside one of the four docker containers.
Moreover, the frontend uses an environment variable called NTI_BUILDOUT_PATH that is defined on the host machine. NTI_BUILDOUT_PATH must point to the buildout directory, which is inside the aforementioned container.
My problem is that I do not know how to define NTI_BUILDOUT_PATH such that it contains a directory that points towards the buildout directory that is needed by the front end for SSL certificates and other purposes.
I have researched around the web and read about volumes and bind mounts but I do not think they can help me in my case.
One way you can do that is by copying your buildout folder into the host machine using docker cp
docker cp <backend-container-id>:<path-to-buildout> <path-to-host-folder>
For Example if your backend's container_id is d1b5365c5bca and your buildout folder is in /app/buildout inside the container. You can use the following command to copy it to the host.
docker cp d1b5365c5bca:/app/buildout /home/mahmoud/app/buildout
After that you docker rm all your containers and recreate new ones with a bind mount to the buildout folder in the host. So following the previous example we'll have
docker run -v /home/mahmoud/app/buildout:/app/buildout your-backend-image
docker run -v /home/mahmoud/app/buildout:/app/buildout -e NTI_BUILDOUT_PATH=/app/buildout your-frontend-image
I have an application in my local host.
The application use files from directory on remote host as data base.
I should docker this application
How can I use this directory?
I tried to use it as volume but it didn't work
the files of the directory are inside container, but the application doesn't recognize it
If you somehow map remote directory into your local host, why not using the same technique inside docker?
If for some reasons you cant (lets say, you don't want to install additional drivers in your container), you still can use volumes:
Lets say on your local host your directory (which is somehow synchronized with remote endpoint) is called /home/sync_folder. Then you start docker in following manner:
docker run -it -v /home/sync_folder:/shares ubuntu ls /shares
I've written ubuntu just as an example. ls /shares illustrates ow to access directory inside container
I am trying to edit cassandra.yaml which is inside docker container at /etc/cassandra/cassandra.yaml, I can edit it from logging inside the container, but how can i do it from host?
Multiple ways to achieve this from host to container. You can simple use COPY or RUN in Dockerfile or with basic linux commands as sed, cat, etc. to place your configuration into the container. Another way you can pass environment variables while running your cassandra image which will pass those environment variables to the spawning container. Also, can use the docker volume mount it from host to container and you can map the configuration you want into the cassandra.yaml as shown below,
$ docker container run -v ~/home/MyWorkspace/cassandra.yaml:/etc/cassandra/cassandra.yaml your_cassandra_image_name
If you are using Docker Swarm then you can use Docker configs to externally store the configuration files(Even other external services can be used as etcd or consul). Hope this helps.
To edit cassandra.yaml :
1) Copy your file from your Docker container to your system
From command line :
docker ps
(To get your container id)
Then :
docker cp your_container_id:\etc\cassandra\cassandra.yaml C:\Users\your_destination
Once the file copied you should be able to see it in your_destination folder
2) Open it and make the changes you want
3) Copy your file back into your Docker container
docker cp C:\Users\your_destination\cassandra.yaml your_container_id:\etc\cassandra
4) Restart your container for the changes to be effective
I am running a docker container on Jenkins. I can't install anything on jenkins, so I did some processing on docker and want to get the results out to the host. If I set an environment variable in the docker container, how do I extract it to my jenkins host?
I can see that I can write the env variable to a file and copy it to the host, but is there another way ?
When running the container, you can mount a file or a folder into the container. Inside your container, you can write to this file and have the changed reflected on the host file on the machine.
To do that create a file result.txt on the host machine and when running the container, specify the -v option to mount the file.
docker run -v ./result.txt:/result.txt ...
And let the jenkins job write the results into this file.
Assume that i have an application with this simple Dockerfile:
//...
RUN configure.sh --logmyfiles /var/lib/myapp
ENTRYPOINT ["starter.sh"]
CMD ["run"]
EXPOSE 8080
VOLUME ["/var/lib/myapp"]
And I run a container from that:
sudo docker run -d --name myapp -p 8080:8080 myapp:latest
So it works properly and stores some logs in /var/lib/myapp of docker container.
My question
I need these log files to automatically saved in host too, So how can i mount the /var/lib/myapp from the container to the /var/lib/myapp in host server (without removing current container) ?
Edit
I also see Docker - Mount Directory From Container to Host, but it doesn't solve my problem i need a way to backup my files from docker to host.
First, a little information about Docker volumes. Volume mounts occur only at container creation time. That means you cannot change volume mounts after you've started the container. Also, volume mounts are one-way only: From the host to the container, and not vice-versa. When you specify a host directory mounted as a volume in your container (for example something like: docker run -d --name="foo" -v "/path/on/host:/path/on/container" ubuntu), it is a "regular ole" linux mount --bind, which means that the host directory will temporarily "override" the container directory. Nothing is actually deleted or overwritten on the destination directory, but because of the nature of containers, that effectively means it will be overridden for the lifetime of the container.
So, you're left with two options (maybe three). You could mount a host directory into your container and then copy those files in your startup script (or if you bring cron into your container, you could use a cron to periodically copy those files to that host directory volume mount).
You could also use docker cp to move files from your container to your host. Now that is kinda hacky and definitely not something you should use in your infrastructure automation. But it does work very well for that exact purpose. One-off or debugging is a great situation for that.
You could also possibly set up a network transfer, but that's pretty involved for what you're doing. However, if you want to do this regularly for your log files (or whatever), you could look into using something like rsyslog to move those files off your container.
So how can i mount the /var/lib/myapp from the container to the /var/lib/myapp in host server
That is the opposite: you can mount an host folder to your container on docker run.
(without removing current container)
I don't think so.
Right now, you can check docker inspect <containername> and see if you see your log in the /var/lib/docker/volumes/... associated to the volume from your container.
Or you can redirect the result of docker logs <containername> to an host file.
For more example, see this gist.
The alternative would be to mount a host directory as the log folder and then access the log files directly on the host.
me#host~$ docker run -d -p 80:80 -v <sites-enabled-dir>:/etc/nginx/sites-enabled -v <certs-dir>:/etc/nginx/certs -v <log-dir>:/var/log/nginx dockerfile/nginx
me#host~$ ls <log-dir>
(again, that apply to a container that you start, not an existing running one)