$(uname -a) returning the same in docker host or any docker container

linux-kernel docker dockerfile uname
Leo Gallucci picture Leo Gallucci · Jun 23, 2015 · Viewed 11.4k times · Source

Why $(uname -a) returns the same Linux kernel than the host machine inside a docker container?

uname -a
#=> Linux leo 3.13.0-55-generic #94-Ubuntu SMP Thu Jun 18 00:27:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

docker run -ti --rm ubuntu:vivid-20150611 uname -a
#=> Linux 147c3aff216b 3.13.0-55-generic #94-Ubuntu SMP Thu Jun 18 00:27:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

Even though my host machine is Ubuntu 14.04 (trusty) while the container is Ubuntu 15.04 (vivid) and should have kernel 3.19

Answer

user4793675 picture user4793675 · Jun 23, 2015

Docker uses the host operating system kernel, there is no custom or additional kernel inside the container. All containers running on the machine are sharing this "host" kernel.

See for more information this question on SuperUser.

Related questions

Privileged containers and capabilities

If I am running a container in privileged mode, does it have all the Kernel capabilities or do I need to add them separately?

Read More
Running docker on Android

With Android 4.4 KitKat, Google is upgrading linux kernel to version 3.8 which is the required kernel version for Docker. I don't know the AUFS part but will there be a way to run docker containers on android with this update?

Read More
Memory Limit and CPU Limit in Docker Container

UPDATE: found a lot of questions and discussions on stackoverflow about this topic. And although they are marked as accepted answered and started by thousands of users, they do not seem to be the right answer here. I ran a …

Read More