how to set ulimit / file descriptor on docker cont

Question

I need to set the file descriptor limit correctly on the docker container I connect to container with ssh (https://github.com/phusion/baseimage-docker)

Already tried:

• edit limits.conf the container ignore this file
• upstart procedure found at https://coderwall.com/p/myodcq but this docker image has different kind of init process. (runit)
• I tried to modify configuration of pam library in /etc/pam.d
• try to enabled pam for ssh in sshd_config

The output it always the same.

bash: ulimit: open files: cannot modify limit: Operation not permitted

Answer 1

The latest docker supports setting ulimits through the command line and the API. For instance, docker run takes --ulimit <type>=<soft>:<hard> and there can be as many of these as you like. So, for your nofile, an example would be --ulimit nofile=262144:262144

Answer 2

I have tried many options and unsure as to why a few solutions suggested above work on one machine and not on others.

A solution that works and that is simple and can work per container is:

docker run --ulimit memlock=819200000:819200000 -h <docker_host_name> --name=current -v /home/user_home:/user_home -i -d -t docker_user_name/image_name

Answer 3

After some searching I found this on a Google groups discussion:

docker currently inhibits this capability for enhanced safety.

That is because the ulimit settings of the host system apply to the docker container. It is regarded as a security risk that programs running in a container can change the ulimit settings for the host.

The good news is that you have two different solutions to choose from.

1. Remove sys_resource from lxc_template.go and recompile docker. Then you'll be able to set the ulimit as high as you like.

or

2. Stop the docker demon. Change the ulimit settings on the host. Start the docker demon. It now has your revised limits, and its child processes as well.

I applied the second method:

1. sudo service docker stop;

2. changed the limits in /etc/security/limits.conf

3. reboot the machine

4. run my container

5. run ulimit -a in the container to confirm the open files limit has been inherited.

See: https://groups.google.com/forum/#!searchin/docker-user/limits/docker-user/T45Kc9vD804/v8J_N4gLbacJ

Answer 4

Actually, I have tried the above answer, but it did not seem to work.

To get my containers to acknowledge the ulimit change, I had to update the docker.conf file before starting them:

$ sudo service docker stop
$ sudo bash -c "echo \"limit nofile 262144 262144\" >> /etc/init/docker.conf"
$ sudo service docker start

Answer 5

The docker run command has a --ulimit flag you can use this flag to set the open file limit in your docker container.

Run the following command when spinning up your container to set the open file limit.

docker run --ulimit nofile=<softlimit>:<hardlimit> the first value before the colon indicates the soft file limit and the value after the colon indicates the hard file limit. you can verify this by running your container in interactive mode and executing the following command in your containers shell ulimit -n

PS: check out this blog post for more clarity

Answer 6

For boot2docker, we can set it on /var/lib/boot2docker/profile, for instance:

ulimit -n 2018

Be warned not to set this limit too high as it will slow down apt-get! See bug #1332440. I had it with debian jessie.