I'm running an Application in tomcat. It generate some application's temp files during the process. And when we shutdown the tomcat using shutdown.sh or stop tomcat from IntelliJ then temp files will be converted to csv. This is inbuilt feature of my Application.
Now when I run the same Application in Docker, then temp is not converting to csv format as I expect it to.
I can see ENTERYPOINT in Docker configuration file that indicates the startup script for the docker. I don't know how docker stop internally works and what it trigger when we execute docker stop <container Name>, or where I should define the script for docker stop.
I also tried docker stop -t 10 <container Name>, with the thought in my mind that it might be tomcat, taking time to shutdown hence docker might be killing the tomcat process. So I tried docker stop with 10 second time also. But no luck.
I think docker is killing the tomcat when I execute docker stop
Any guidance will be appreciated.
First check this reference for process with pid 1.
Step to perform in your system.
Step 1 :- in entrypoint check your script file.
Step 2 :- update your script line entry.sh, find some line where you're starting your tomcat.
Step 3 :- for start tomcat use "exec sh catalina.sh run".
Step 4 :- check your ps with "docker exec ps -ef" it must be run on pid 1
Step 5 :- rebuild docker image.
Step 6 :- docker stop will send shutdown signal to tomcat and works.
For observe logs use docker logs -f <container_name>
Related
I created Dockerfile with the following content,
FROM node:16.4.2-alpine3.14
WORKDIR /app
COPY package.json .
COPY . /app
then I created image,
docker build -t app:0.1 .
and then started the container by running,
docker run -it app:0.1
It opened the node shell.
I then closed it.
Doing docker ps -a gives the following output,
Now,
I want to restart the same container and with node shell. How can it be done?
It shows as exited since there is no process running. To start it again , you can use the docker start command with -i flag.
https://docs.docker.com/engine/reference/commandline/start/ for more options
docker rm the existing container and docker run a new one. Consider using the docker run --rm option so the container deletes itself when it's done.
There's nothing special or valuable about a container; it's just a wrapper around a single process (in your case the Node REPL), and creating a new one isn't especially expensive. In the same way that you can't restart the REPL once you've exited it but need to re-run node, you generally will want to delete and recreate containers once their process has finished. With longer-running processes this also helps ensure the process's filesystem is exactly what you expect: if something exits unexpectedly, deleting the container will also remove any temporary files or lock files it's left behind, so restarting the container will run successfully.
use the following sequence of commands:
docker container start magical_merkle
docker attach magical_merkle
Explanation: the first command restarts your exited container, but in detached mode, it means it's running in the background and you can't see it's output. now for you to reattach to the container you run attach command of docker (second command) which attaches the std io of your host terminal to the std io of the running container.
you may notice the magical_merkle in the commands. this is the name of your container as found in the container ls output you provided. when you run the run command, docker will name the container with a auto generated name if you don't provide one for it.
I'm fairly new to Docker. I have a long Dockerfile that I inherited from a previous developer, which has many errors and I'm trying to get it back to a working point. I commented out most of the file except for just the first line:
FROM ubuntu:14.04
I did the following:
docker build -t pm . to build the image - this works because I can see the image when I execute docker images
docker run <image-id> returns without error or any message. Now I'm expecting the container to be created from the image and started. But when I do a docker ps -a it shows the container exited:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b05f9727f516 f216cfb59484 "/bin/bash" About a
minute ago Exited (0) About a minute ago
lucid_shirley
Not sure why can't I get a running container and why does it keep stopping after the docker run command.
executing docker logs <container_id> displays nothing - it just returns without any output.
Your Docker image doesn’t actually do anything, container stop when finish its job. Since here no foreground process running it will start and then immediately stop.
To confirm your container have no issues, try to put below code into a docker-compose.yml(in same folder as the Dockerfile) and run docker-compose up, now you will see your container is running without exiting.
version: '3'
services:
my-service:
build: .
tty: true
Please have a look here Docker official tutorial it will guide you to how to work with docker.
try
docker run -it <image> /bin/bash
to run a shell inside the container.
That won't do much for you, but that'll show you what is happening: as soon as you exit the shell, it will exit the container too.
Your container basically doesn't do anything: it has an image of Ubuntu but doesn't have an ENTRYPOINT or a CMD command to run 'something'
Containers are ephemeral when ran: they run a single command and exit when the command finishes.
Docker container categorized following way.
Task Based : When container start it will start processing and it complete the process then exited.
Background container : It will wait for some request.
As you not provided your docker file so I assume that you have only one statement.
FROM ubuntu:14.04
your build statement create image with name pm.
Now you run
docker run pm
It will start container and stop as you did not provide any entry point.
Now try this
This is one command prompt or terminal.
docker run -it pm /bin/bash
Open another terminal or command prompt.
docker ps ( Now you will see there is one container).
If you want to see container that is continuously running then use following image.
(This is just a example)
docker run -d -p 8099:80 nginx
Above line run one container with Nginx image and when you open your browser http://localhost:8099 you can see the response.
Docker Containers are closely related to the process they are running. This process is specified by the "CMD" part on the Dockerfile. This process has the PID "1". If you kill it, your container is killed. If you haven't one, your container will stop instantly. In your case, you have to "override" your CMD. You can do it with a simple : "docker run -it ubuntu:18.04 bash". "-it" is mandatory since it allows the stdin to be attached to your container.
Have fun with docker.
Each instruction of Dockerfile is a layer within a container which perform some task. In your docker file It's just the loading the ubuntu which is completed when you run the docker within a fraction of seconds and exit since process finished. So if want to have your container running all the time then there should be a foreground process running in your docker.
For testing if you run
docker run <imageid> echo hi it will return the output means your container is fine.
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.
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.
I am trying to create docker container using dockerfile where script-entry.sh is to be executed when the containers starts and script-exit.sh to be executed when the container stops.
ENTRYPOINT helped to accomplish the first part of the problem where script-entry.sh runs on startup.
How will i make sure the script-exit.sh is executed on docker exit/stop ?
docker stop sends a SIGTERM signal to the main process running inside the Docker container (the entry script). So you need a way to catch the signal and then trigger the exit script.
See This link for explanation on signal trapping and an example (near the end of the page)
Create a script, and save it as a bash file, that contains that following:
$CONTAINER_NAME="someNameHere"
docker exec -it $CONTAINER_NAME bash -c "sh script-exit.sh"
docker stop $CONTAINER_NAME
Run that file instead of running docker stop, and that should do the trick. You can setup an alias for that as well.
As for automating it inside of Docker itself, I've never seen it done before. Good luck figuring it out, if that's the road you want to take.