I would like to stop my running docker container after a specific time, let's say 2 hrs after startup. So far my research has led to the following solutions. I just wanted to know if there were better ways to do it.
Use a cron job to stop the container by calling the docker stop command.
Use an entry point like sleep 5000, but this does not suit my use case.
Using --stop-timeout in the docker run command ; I believe this is just the maximum timeout given for the container to gracefully shutdown. Am I missing something
here?
You can use the timeout command that's part of the coreutils package which is already installed in the debian images (and probably many others).
This will run the container for 30 seconds and then stop
docker run debian timeout 30 tail -f /dev/null
Basically, add timeout 7200 in front of the command you want to run in the container, and it'll be killed after 2 hours.
I have a docker container that internally starts a server. (I don't own this. I am just reusing it)
Once the server starts, I am running some curl commands that hit this server.
I am running the above steps in a script. Here's the issue:
the docker container starts but internally I think it is taking some time to actually start the server in it.
Before that server is up and running, it looks like the curl commands start executing and give an error that server could not be found. If I manually run this a few seconds later, it works fine though.
Please let me know if there is a way to solve this. I don't think using entry point or CMD will work for similar reasons.
Also, if that matters, the server I am using is kong.
thanks, Om.
The general answer to this is to perform some sort of health check; once you've verified that the server is healthy you can start making live requests to it. As you've noticed, the container existing or the server process running on its own isn't enough to guarantee that the container can handle requests.
A typical approach to this is to make some request to the server that will fail until the server is ready. You don't need to modify the container to do this. In some environments like Kubernetes, you can specify health checks or probes as part of the deployment configuration, but for a simple shell script, you can just run curl in a loop:
docker run -p 8080:8080 -d ...
RUNNING=false
for i in $(seq 30); do
# Try GET / and see if it succeeds
if curl -s http://localhost:8080/
then
echo Server is running
RUNNING=true
break
else
echo Server not running, waiting
sleep 1
fi
done
if [ "$RUNNING" = false ]; then
echo Server did not start within 30s
# docker stop ... && docker rm ...
exit 1
fi
If you just need to know the port is up, this simple script is very handy:
https://github.com/vishnubob/wait-for-it
How would you run a daemon or background process in Docker? I've seen some suggestions, like this answer that launches supervisor from CMD.
However, I'm trying to test a server configuration tool that connects via SSH. So I need to launch the SSH daemon in the background, and then run my tool.sh to test connecting via SSH to its own container. I need to monitor my tool's output in order to verify it's working. What's the best way to accomplish this?
Is there any way to make a RUN command run in the background, like RUN /usr/sbin/sshd -D & or would I have to have some wrapper script launched from CMD that does something like this?
#!/bin/bash
/usr/sbin/sshd -D
tool.sh
You can run a daemon inside a docker container the same as you would on a bare metal linux machine. The only hard part is getting it to start without the nice runlevel scripts to help.
How about this:
#!/bin/sh
function run_script() {
ssh_pids=0
while [ ${ssh_pids} -lt 1 ]; do
sleep 5
ssh_pids=$(pgrep sshd | wc -l)
done
test.sh
}
run_script &
sshd -D > /dev/null 2>&1
I've used this trick before to do what you describe, and it's worked OK. It will just background the call to run_script and proceed to start SSHD in non-daemon mode, piping it to /dev/null. Meanwhile, run_script polls for sshd; when it finds it, it quits polling and runs test.sh, which should still have the terminal as it's stdout. you'll probably need to use some external kill signal to stop the whole thing, once test.sh is done.
If you don't like this tomfoolery, the other option would be to do as you described: write a wrapper script to use as the CMD/ENTRYPOINT, and have it start SSHD without the debug flag, and then start test.sh.
The advantage of doing it with the script I posted is that the container will stick around after test.sh is finished, so you can log in and poke around, while also making your script wait until the daemon is running.
I'm benchmarking a tool that monitors docker containers. To do that I need to launch several dummy containers with an orchestration tool such Kubernetes. The containers should be lightweight and shouldn't take any of the machine resources (e.g. ports), since the idea is to run 15 or more of these dummy containers in each machine of a cluster. I don't care about what the container does as long as it keeps running as a daemon and I can monitor it for a long period of time.
Is there any Docker image that meets these requirements and that I can use straight out of the box?.
You can just run an alpine container with a sleep command.
Something like this:
docker run -d alpine sh -c 'while sleep 3600; do :; done'
I know it is more than a year old but I found this (source) from luca3m that may help others.
I've seen a bunch of tutorials that seem do the same thing I'm trying to do, but for some reason my Docker containers exit. Basically, I'm setting up a web-server and a few daemons inside a Docker container. I do the final parts of this through a bash script called run-all.sh that I run through CMD in my Dockerfile. run-all.sh looks like this:
service supervisor start
service nginx start
And I start it inside of my Dockerfile as follows:
CMD ["sh", "/root/credentialize_and_run.sh"]
I can see that the services all start up correctly when I run things manually (i.e. getting on to the image with -i -t /bin/bash), and everything looks like it runs correctly when I run the image, but it exits once it finishes starting up my processes. I'd like the processes to run indefinitely, and as far as I understand, the container has to keep running for this to happen. Nevertheless, when I run docker ps -a, I see:
➜ docker_test docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c7706edc4189 some_name/some_repo:blah "sh /root/run-all.sh 8 minutes ago Exited (0) 8 minutes ago grave_jones
What gives? Why is it exiting? I know I could just put a while loop at the end of my bash script to keep it up, but what's the right way to keep it from exiting?
If you are using a Dockerfile, try:
ENTRYPOINT ["tail", "-f", "/dev/null"]
(Obviously this is for dev purposes only, you shouldn't need to keep a container alive unless it's running a process eg. nginx...)
I just had the same problem and I found out that if you are running your container with the -t and -d flag, it keeps running.
docker run -td <image>
Here is what the flags do (according to docker run --help):
-d, --detach=false Run container in background and print container ID
-t, --tty=false Allocate a pseudo-TTY
The most important one is the -t flag. -d just lets you run the container in the background.
This is not really how you should design your Docker containers.
When designing a Docker container, you're supposed to build it such that there is only one process running (i.e. you should have one container for Nginx, and one for supervisord or the app it's running); additionally, that process should run in the foreground.
The container will "exit" when the process itself exits (in your case, that process is your bash script).
However, if you really need (or want) to run multiple service in your Docker container, consider starting from "Docker Base Image", which uses runit as a pseudo-init process (runit will stay online while Nginx and Supervisor run), which will stay in the foreground while your other processes do their thing.
They have substantial docs, so you should be able to achieve what you're trying to do reasonably easily.
you can run plain cat without any arguments as mentioned by bro #Sa'ad to simply keep the container working [actually doing nothing but waiting for user input] (Jenkins' Docker plugin does the same thing)
The reason it exits is because the shell script is run first as PID 1 and when that's complete, PID 1 is gone, and docker only runs while PID 1 is.
You can use supervisor to do everything, if run with the "-n" flag it's told not to daemonize, so it will stay as the first process:
CMD ["/usr/bin/supervisord", "-n"]
And your supervisord.conf:
[supervisord]
nodaemon=true
[program:startup]
priority=1
command=/root/credentialize_and_run.sh
stdout_logfile=/var/log/supervisor/%(program_name)s.log
stderr_logfile=/var/log/supervisor/%(program_name)s.log
autorestart=false
startsecs=0
[program:nginx]
priority=10
command=nginx -g "daemon off;"
stdout_logfile=/var/log/supervisor/nginx.log
stderr_logfile=/var/log/supervisor/nginx.log
autorestart=true
Then you can have as many other processes as you want and supervisor will handle the restarting of them if needed.
That way you could use supervisord in cases where you might need nginx and php5-fpm and it doesn't make much sense to have them apart.
Motivation:
There is nothing wrong in running multiple processes inside of a docker container. If one likes to use docker as a light weight VM - so be it. Others like to split their applications into micro services. Me thinks: A LAMP stack in one container? Just great.
The answer:
Stick with a good base image like the phusion base image. There may be others. Please comment.
And this is yet just another plead for supervisor. Because the phusion base image is providing supervisor besides of some other things like cron and locale setup. Stuff you like to have setup when running such a light weight VM. For what it's worth it also provides ssh connections into the container.
The phusion image itself will just start and keep running if you issue this basic docker run statement:
moin#stretchDEV:~$ docker run -d phusion/baseimage
521e8a12f6ff844fb142d0e2587ed33cdc82b70aa64cce07ed6c0226d857b367
moin#stretchDEV:~$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS
521e8a12f6ff phusion/baseimage "/sbin/my_init" 12 seconds ago Up 11 seconds
Or dead simple:
If a base image is not for you... For the quick CMD to keep it running I would suppose something like this for bash:
CMD exec /bin/bash -c "trap : TERM INT; sleep infinity & wait"
Or this for busybox:
CMD exec /bin/sh -c "trap : TERM INT; (while true; do sleep 1000; done) & wait"
This is nice, because it will exit immediately on a docker stop.
Just plain sleep or cat will take a few seconds before the container is forcefully killed by docker.
Updates
As response to Charles Desbiens concerning running multiple processes in one container:
This is an opinion. And the docs are pointing in this direction. A quote: "It’s ok to have multiple processes, but to get the most benefit out of Docker, avoid one container being responsible for multiple aspects of your overall application." For sure it obviously much more powerful to devide your complex service into multiple containers. But there are situations where it can be beneficial to go the one container route. Especially for appliances. The GitLab Docker image is my favourite example of a multi process container. It makes deployment of this complex system easy. There is no way for mis-configuration. GitLab retains all control over their appliance. Win-Win.
Make sure that you add daemon off; to you nginx.conf or run it with CMD ["nginx", "-g", "daemon off;"] as per the official nginx image
Then use the following to run both supervisor as service and nginx as foreground process that will prevent the container from exiting
service supervisor start && nginx
In some cases you will need to have more than one process in your container, so forcing the container to have exactly one process won't work and can create more problems in deployment.
So you need to understand the trade-offs and make your decision accordingly.
Since docker engine v1.25 there is an option called init.
Docker-compose included this command as of version 3.7.
So my current CMD when running a container that should run into infinity:
CMD ["sleep", "infinity"]
and then run it using:
docker build
docker run --rm --init app
crf.:
rm docs and init docs
Capture the PID of the ngnix process in a variable (for example $NGNIX_PID) and at the end of the entrypoint file do
wait $NGNIX_PID
In that way, your container should run until ngnix is alive, when ngnix stops, the container stops as well
Along with having something along the lines of : ENTRYPOINT ["tail", "-f", "/dev/null"] in your docker file, you should also run the docker container with -td option. This is particularly useful when the container runs on a remote m/c. Think of it more like you have ssh'ed into a remote m/c having the image and started the container. In this case, when you exit the ssh session, the container will get killed unless it's started with -td option. Sample command for running your image would be: docker run -td <any other additional options> <image name>
This holds good for docker version 20.10.2
There are some cases during development when there is no service yet but you want to simulate it and keep the container alive.
It is very easy to write a bash placeholder that simulates a running service:
while true; do
sleep 100
done
You replace this by something more serious as the development progress.
How about using the supervise form of service if available?
service YOUR_SERVICE supervise
Once supervise is successfully running, it will not exit unless it is
killed or specifically asked to exit.
Saves having to create a supervisord.conf