I have a node docker container on which i'm running a dev server.
In my docker-compose.yml file, the entry command is :
...
command: start-dev-server
...
Where start-dev-server points to a script that starts the server after a vendor install :
// /usr/local/bin/start-dev-server
#!/usr/bin/env bash
# install node modules if missing
npm i
# start the dev server
npm run start
So when I start my container, the server will also start.
I know that I can access my container in bash via the following command :
docker exec -it my-container bash
But there I can't stop or restart my server.
Is there a way to access the ssh with the started command ? (to see the server logs for example, or to stop & restart it).
Maybe I take it by the wrong path here because the entry command isn't supposed to be stopped ? So in this case, would anyone has a solution that could allow me to start my server & control it in a more flexible way ?
The best practices says that you should see the container as your server. If you want to stop it, stop the container (docker stop my-container), if you want to restart it, restart the container (docker restart my-container). Your server should log to stdout, so you can see the logs using docker logs -f my-container. So, you're right, the command isn't supposed to be stopped, as it will stop the container.
Related
I have a docker service/image I'm using which restarts as soon as starts.
I'm unable to fix the issue by getting into the container using
docker exec -it CONTAIER_NAME
since it restarts/terminates as soon as it boots.
Is there anyway I can pause it directly? I can't rebuild the image as I don't have access to the internet on the server. (Yes I'm sure the rebuild or build--no-cache will fix the issue)
The issue should be easily fixable if I modify permissions for a certain folder, but I'm not sure how to do this inside the container when I can't access it. The image doesn't have a docker file and is used directly from the docker hub.
If we do not get any information from the container's logs, we have the option to start the process "manually". For this, we start the container with an interactive terminal (-it, -i to keep STDIN open, -t to open a pseudo-TTY) and override the entrypoint to be a shell, e.g. bash. For good measure, we want the container to be removed when it terminates (i.e. when we exit the termainal, --rm):
docker run ... -it --rm --entrypoint /bin/bash
Once inside the container, we can start the process that would have normally started through the entrypoint from the container's terminal and extract error information from here.
I'm pretty green regarding docker and find myself facing the following problem:
I'm trying to create a dockerfile to generate an image with my companie software on it. During the installation of that software the install process check if ssh is running with the following command:
if [ $(pgrep sshd | wc -l) -eq 0 ]; then
I probably need to precise that I'm installing and starting open-ssh during that same process.
Can you at all check that a service is running during the image creation ?
I cannot ignore that step has it is executed as part of a self extracting mechanism.
Any clue toward the right direction would be appreciated.
An image cannot run services. You are just creating all the necessary things needed for your container to run, like installing databases, servers, or copying some config files etc in the Dockerfile. The last step in the Dockerfile is where you can give instructions on what to do when you issue a docker run command. A script or command can be specified using CMD or ENTRYPOINT in the Dockerfile.
To answer your question, during the image creation process, you cannot check whether a service is running or not. When the container is started, docker will execute the script or command that you can specify in the CMD or ENTRYPOINT. You can use that script to check if your services are running or not and take necessary action after that.
It is possible to run services during image creation. All processes are killed once a RUN command completes. A service will not keep running between RUN commands. However, each RUN command can start services and use them.
If an image creation command needs a service, start the service and then run the command that depends on the service, all in one RUN command.
RUN sudo service ssh start \
&& ssh localhost echo ok \
&& ./install
The first line starts the ssh server and succeeds with the server running.
The second line tests if the ssh server is up.
The third line is a placeholder: the 'install' command can use the localhost ssh server.
In case the service fails to start, the docker build command will fail.
I spent the weekend pouring over the Docker docs and playing around with the toy applications and example projects. I'm now trying to write a super-simple web service of my own and run it from inside a container. In the container, I want my app (a Spring Boot app under the hood) -- called bootup -- to have the following directory structure:
/opt/
bootup/
bin/
bootup.jar ==> the app
logs/
bootup.log ==> log file; GETS CREATED BY THE APP # STARTUP
config/
application.yml ==> app config file
logback.groovy ==> log config file
It's very important to note that when I run my app locally on my host machine - outside of Docker - everything works perfectly fine, including the creation of log files to my host's /opt/bootup/logs directory. The app endpoints serve up the correct content, etc. All is well and dandy.
So I created the following Dockerfile:
FROM openjdk:8
RUN mkdir /opt/bootup
RUN mkdir /opt/bootup/logs
RUN mkdir /opt/bootup/config
RUN mkdir /opt/bootup/bin
ADD build/libs/bootup.jar /opt/bootup/bin
ADD application.yml /opt/bootup/config
ADD logback.groovy /opt/bootup/config
WORKDIR /opt/bootup/bin
EXPOSE 9200
ENTRYPOINT java -Dspring.config=/opt/bootup/config -jar bootup.jar
I then build my image via:
docker build -t bootup .
I then run my container:
docker run -it -p 9200:9200 -d --name bootup bootup
I run docker ps:
CONTAINER ID IMAGE COMMAND ...
3f1492790397 bootup "/bin/sh -c 'java ..."
So far, so good!
My app should then be serving a simple web page at localhost:9200, so I open my browser to http://localhost:9200 and I get nothing.
When I use docker exec -it 3f1492790397 bash to "ssh" into my container, I see everything looks fine, except the /opt/bootup/logs directory, which should have a bootup.log file in it -- created at startup -- is instead empty.
I tried using docker attach 3f1492790397 and then hitting http://localhost:9200 in my browser, to see if that would generated some standard output (my app logs both to /opt/bootup/logs/bootup.log as well as the console) but that doesn't yield any output.
So I think what's happening is that my app (for some reason) doesn't have permission to create its own log file when the container starts up, and puts the app in a weird state, or even prevents it from starting up altogether.
So I ask:
Is there a way to see what user my app is starting up as?; or
Is there a way to tail standard output while the container is starting? Attaching after startup doesn't help me because I think by the time I run the docker attach command the app has already choked
Thanks in advance!
I don't know why your app isn't working, but can answer your questions-
Is there a way to see what user my app is starting up as?; or
A: Docker containers run as root unless otherwise specified.
Is there a way to tail standard output while the container is starting? Attaching after startup doesn't help me because I think by the time I run the docker attach command the app has already choked
A: Docker containers dump stdout/stderr to the Docker logs by default. There are two ways to see these- 1 is to run the container with the flag -it instead of -d to get an interactive session that will list the stdout from your container. The other is to use the docker logs *container_name* command on a running or stopped container.
docker attach 3f1492790397
This doesn't do what you are hoping for. What you want is docker exec (probably docker exec -it bootup bash), which will give you a shell in the scope of the container which will let you check for your log files or try and hit the app using curl from inside the container.
Why do I get no output?
Hard to say without the info from the earlier commands. Is your app listening on 0.0.0.0 or on localhost (your laptop browser will look like an external machine to the container)? Does your app require a supervisor process that isn't running? Does it require some other JAR files that are on the CLASSPATH on your laptop but not in the container? Are you running docker using Docker-Machine (in which case localhost is probably not the name of the container)?
I am new to docker and I tried to run the linuxconfig/lemp-php7 image. Everything worked fine and I could access the nginx web server installed on the container. To run this image I used this command:
sudo docker run linuxconfig/lemp-php7
When I tried to run the image with the following command to gain access over the container through bash I couldn't connect to nginx and I got the connection refused error message. Command: sudo docker run -ti linuxconfig/lemp-php7 bash
I tried this several times so I'm pretty sure it's not any kind of coincidence.
Why does this happen? Is this a problem specific to this particular image or is this a general problem. And how can I gain access to the shell of the container and access the web server at the same time?
I'd really like to understand this behavior to improve my general understanding of docker.
docker run runs the specified command instead of what that container would normally run. In your case, it appears to be supervisord, which presumably in turn runs the web server. So you're preventing any of that from happening.
My preferred method (except in cases where I'm trying to debug cases where the container won't even start properly) is to do the following after running the container normally:
docker exec -i -t $CONTAINER_ID /bin/bash
I have a docker image that runs play web application. In dockerfile there is CMD which starts the server and it waits until you hit Ctrl+D to exit. If I do:
docker run -d -i -v
It works correctly - starts the server and waits for ctrl+D.
This is however not the case when i start the container:
docker start -i
Instead the server automatically stops:
--- (Running the application, auto-reloading is enabled) ---
[info] p.c.s.NettyServer - Listening for HTTP on /0:0:0:0:0:0:0:0:9000
(Server started, use Ctrl+D to stop and go back to the console...)
[success] Total time: 1 s, completed Jul 27, 2016 11:54:13 AM <--- this indicates that the server was stopped.
How can I force docker start to not stop server?
A docker container exits when its main process finishes. Without having an insight into your docker-file (I have no experience with the play framework), you need to make sure that at least one process stays alive.
You have a couple of options:
Docker Way
Try using -it like docker run -it <your framework image> bash to get into the container you are starting. This should keep your window open and allow you to run commands in the container.
Docker "debug" way
Try using the docker inspect <your container> (use docker ps -a to find your container) command to investigate why the container exited. In case you have a start script like start.sh you can try to add while true; do sleep 1000; done to keep the container up to investigate on what it was doing before it exited.
Try using the one of the published docker images like - https://hub.docker.com/r/ingensi/play-framework/
P.S. I can not loose the feeling that you are new to docker and are mixing the docker start and the docker run command.