I'd like to install mysql server on a centos:6.6 container.
However, when I run docker run --name myDB -e MYSQL_ROOT_PASSWORD=my-secret-pw -d centos:6.6, I got docker: Error response from daemon: No command specified. error.
Checking the document from docker run --help, I found that the COMMAND seems to be an optional argument when executing docker run. This is because [COMMAND] is placed inside a pair of square brackets.
$ docker run --help
Usage: docker run [OPTIONS] IMAGE [COMMAND] [ARG...]
Run a command in a new container
I also find out that the official repository of mysql doesn't specify a command when starting a MySQL container:
Starting a MySQL instance is simple:
$ docker run --name some-mysql -e MYSQL_ROOT_PASSWORD=my-secret-pw -d mysql:tag
Why should I provide a command when running a centos:6.6 container, but not so when running a mysql container?
I'm guessing that maybe centos:6.6 is specially-configured so that the user must provide a command when running it.
if you use centos:6.6, you do need to provide a command when you issue "docker run" command.
The reason the officical repository of mysql does not specify a command is because it has CMD command in it's docker file: CMD ["mysqld"]. Check it's docker file here.
The CMD in docker file is the default command when run the container without a command.
You can read here to better understand what you can use in a docker file.
In your case, you can
Start your centos 6.6 container
Take official mysql docker file as reference, issue similar command (change apt-get to yum ( or sudo yum if you don't use the default root user)
Once you can successfully start mysql, you can put all your command in your docker file, just to make sure the first line is "From centos:6.6"
Build your image
Run a container with your image, then you don't need to provide a command in docker run
You can share your docker file in docker hub, so that other people can user yours.
good luck.
Related
I have created a docker image that includes some python code and a shell script that can execute it. It is going to process a bunch of images from the host system.
This command should create a new contaier and run it.
sudo docker run -v /host/folder:/container/folder opencv:latest bash /extract-embeddings.sh
At the end, the container exits. If I type the same command, then another container is created and exited at completion. But how is the correct usage of containers? Should I use restart, start or run (and then clean up exited containers after)? It just seems unnessary to create a new container each time.
I basically just want a docker image containing some code and 3-4 different commands I can execute whenever needed.
And the docker start command doesn't seem to accept "bash /extract-embeddings.sh" as parameters, instead things bash and extract-embeddings.sh are containers. So maybe I am misunderstanding the lifecycle of containers or the usage.
edit:
Got it to work with:
docker run -t -d --name opencv -v /host/folder:/container/folder
docker exec -it opencv bash /extract-embeddings.sh
You can write the Dockerfile to create your docker image and keep the scripts into it-
Dockerfile:
FROM opencv:latest
COPY ./your-script /some_folder
Create image:
docker build -t my_image .
Run your container:
docker run -d --name my_container
Run the script inside the container:
docker exec -it <container_id_or_name> bash /some_folder/your-script
Build your own docker image that starts with opencv:latest and give the command you run as the entrypoint. Dockerfile could be like
FROM opencv:latest
CMD ["/bin/bash", "/extract-embeddings.sh"]
Use docker create to create a named container.
sudo docker create --name=processmyimage -v /host/folder:/container/folder myopencv:latest
Then use docker start each time you want to run it.
sudo docker start processmyimage
This works well if there is only one command you want to run. If there is more than one command, I would take the approach of building an image that runs unrelated command forever (like a tail -f < /dev/null). Then you can use
sudo docker exec -d /bin/bash < cmd-to-run >
for each command
It's CentOS 7, already installed vi and vim in my CentOS and I can use them. I run docker in CentOS, when I excute this line below:
docker exec -it mysolr /bin/bash
I cannot use vi/vim in the solr container:
bash: vim: command not found
Why is that and how do I fix it so I can use vi/vim to edit file in docker container?
A typical Docker image contains a minimal set of libraries and utilities to run one specific program. Additionally, Docker container filesystems are not long-lived: it is extremely routine to delete and recreate a container, for instance to use a newer version of a base image.
The upshot of this is that you never want to directly edit files in a Docker container, and most images aren't set up with "rich" editing tools. (BusyBox contains a minimal vi and so most Alpine-based images will too.) If you make some change, it will be lost as soon as you delete the container. (Similarly, you usually can install vim or emacs or whatever, but it will get lost as soon as the container is deleted: installing software in a running container isn't usually a best practice.)
There are two good ways to deal with this, depending on what kind of file it is.
If the file is part of the application, like a source file, edit, debug, and test it outside of Docker space. Once you're convinced it's right (by running unit tests and by running the program locally), docker build a new image with it, and docker run a new container with the new image.
ed config.py
pytest
docker build -t imagename .
docker run -d -p ... --name containername imagename
...
ed config.py
pytest
docker build -t imagename .
docker stop containername
docker run -d -p ... --name containername imagename
If the file is configuration that needs to be injected when the application starts, the docker run -v option is a good way to push it in. You can directly edit the config file on your host, but you'll probably need to restart (or delete and recreate) the container for it to notice.
ed config.txt
docker run \
-v $PWD/config.txt:/etc/whatever/config.txt \
--name containername -p ... \
imagename
...
ed config.txt
docker stop containername
docker rm containername
docker run ... imagename
I started to experiment with the docker but have some questions regarding how to develop on it and regarding its use cases. If anyone could guide me through these questions, it will be much appreciated.
First,
As far as I understood, docker is used mainly for developing applications on custom environments, thus avoiding the tidious installation processes. This is initially my intention, why I'd like to use docker for.
I've created a docker file which builds successfuly, and which has basic C++ development tools based upon library/gcc. I want to be able to develop in this docker container as you would do on your terminal.
What I did is I created a docker image from a Dockerfile. (I can observe that it is successfully created)
docker build -t mydockerimage .
Then run the docker in detached mode.
docker run -d mydockerimage
At this point, I am notified with the ID of the docker container. However docker container does not seem to be running when I check the output of:
docker container ls
Here comes the first question, why is my docker container not running?
To my understanding, simplest way to interact with the docker container is as follows:
docker exec -it <container_id_or_name> echo "Hello from container!"
Is this true? Is this a use case of docker in which I simply can start the container and exec some Linux command on it?
Moreover, I get a permission denied on /var/lib/docker.sock when I try to execute docker commands without sudo. What am I missing here?
Thank you in advance.
Do you provide an entrypoint or CMD in your dockerfile? This will be executed inside your container and keeps the container running. You can find some details here.
In short. Docker has a default entrypoint: /bin/sh -c, but no default CMD.
Check the dockerfile of ubuntu. This has bash as CMD so it's executing /bin/sh -c bash.
$ docker run -it ubuntu bash
root#9855e779cab2:/#
This will result in an interactive shell in which you can execute commands like on an ubuntu. If you exit the container the container will stop running.
To keep a container running you can use the -d option. It will run the container in the background as a daemon:
$ docker run -d -it ubuntu bash
2606ad8e095baa0237cc30e599a26a4d727d99d47392d779fb83cd50f1a39614
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2606ad8e095b ubuntu "bash" 18 seconds ago Up 17 seconds cranky_johnson
Now you can exec inside the container to "go inside" the container and execute ubuntu commands.
$ docker exec -it 2606ad8e095b bash
root#2606ad8e095b:/#
When you exit the container it remains running in the background.
Now we can execute your command too:
$ docker exec -it 2606ad8e095b echo "Hello from container!"
Hello from container!
This will open a bash session in your container and echo the string.
I think it's important in your case you define some entrypoint (which can also be a script) or a CMD. Probably you need something very similar to Ubuntu when you just want to use bash inside your container.
Moreover, I get a permission denied on /var/lib/docker.sock when I try to execute docker commands without sudo. What am I missing here?
This is normal. The Docker daemon currently requires root privileges. So you have to use docker with your root user or users which have root priviledges and you have to add sudo every time. You can add your user to a docker group. Every time the daemon starts, it makes the ownership of the Unix socket read/writable by the docker group. This means you can use docker without using sudo everytime when that user is inside your docker group.
To add your user to the docker group:
$ sudo groupadd docker
$ sudo usermod -aG docker $USER
$ exit
ssh back or open new shell
Dockerfile contains
FROM java:8
Iam running this by mounting my host directory into docker by following command
docker run -it -p 8585:9090 -v ~/Docker/:/data d23bdf5b1b1b /data/bin/script.sh
I am able to run this successfully but the problem is when i try to access it from browser i am not able to see anything because of port conflicting
,2 services are running on same port ..
How to solve this ?
Your problem is that you are trying to run a script in a new container and that container then exists. It has nothing to with any existing container that is running.
Also when your specify a command to be run with docker it would not run the CMD command that you had defined while building the Dockerfile.
So what you need to do is below.
docker run -d -p 8585:9090 -v ~/Docker/:/data d23bdf5b1b1b
After the above container is run it will print the ID of the new container. Now you want to execute your command in this new container
docker exec -it <containerid> /data/bin/script.sh
I am using nodeBB to start a server you can run ./nodebb start to stop you can do ./nodebb stop. Now that I have dockerized it http://nodebb-francais.readthedocs.org/projects/nodebb/en/latest/installing/docker/nodebb-redis.html I am not sure how I can interact with it.
I have followed the steps "Using docker-machine mac os x"
docker run --name my-forum-redis -d -p 6379:6379 nodebb/docker:ubuntu-redis
Then
docker run --name my-forum-nodebb --link my-forum-redis:redis -p 80:80 -p 443:443 -p 4567:4567 -P -t -i nodebb/docker:ubuntu
Then
docker start my-forum-nodebb
I had an issue with redis address in use, so I want to fix that and restart but I am not sure how? Also I would like to issue the command grunt in the project directory, again not sure how?
My question is how can I interact with an app inside a docker container as if I had direct access to the project folder itself? Am I missing something?
All code in this answer is untested, as I'm currently at a computer without docker.
See whether the containers are still running
docker ps
Stop misconfigured containers
docker stop my-forum-redis
docker stop my-forum-nodebb
Remove misconfigured containers and their volumes
(The docker images they are based on will be retained.)
docker rm --volumes --force stop my-forum-nodebb
docker rm --volumes --force my-forum-redis
Start again
Then, issue your 3 commands again, now with the correct ports.
Execute arbitrary commands inside container
Also I would like to issue the command grunt in the project directory, again not sure how?
You probably want to do the following after the docker run --name my-forum-nodebb ... command but before docker start my-forum-nodebb.
docker run accepts a command to execute instead of the container's default command. Let's first use this to find out where in the container we'd land:
docker run my-forum-nodebb pwd
If that is the directory where you want to run grunt, just go forward with it:
docker run my-forum-nodebb grunt
If not, you'll have to stuff several commands into a single one. You can do that by invoking a shell:
docker run my-forum-nodebb bash -c 'cd /path/to/project/dir; grunt'
where /path/to/project/dir is to be replaced by where you want to run grunt.