What does COMMAND label means in docker container list?

Question

I am just starting with docker and I have a silly question. When you list all the containers, you'll see an output like this:

CONTAINER ID        IMAGE                        COMMAND                CREATED              STATUS              PORTS               NAMES
4c01db0b339c        ubuntu:12.04                 bash                   17 seconds ago       Up 16 seconds       3300-3310/tcp       webapp
d7886598dbe2        crosbymichael/redis:latest   /redis-server --dir    33 minutes ago       Up 33 minutes       6379/tcp            redis,webapp/db

I am wondering what does the COMMAND here signifies? Does it mean the last command run by the container or the first one or something else?

I tried the official docker documentation but couldn't find my answer. Any help?

kstromeiraos · Accepted Answer · 2017-06-20T09:15:59.003

4

COMMAND is the command executed by the container by default when it's started.

When a container is started, a main command is executed, and the container will live until that command finishs. That CMD will be PID 1 inside the container.

In a Dockerfile you specify that command by CMD instruction.

Also, I recommend you to take a look to this thread to be aware of the difference between CMD and ENTRYPOINT: What is the difference between CMD and ENTRYPOINT in a Dockerfile?

edited Jun 20 '17 at 09:15

answered Jun 20 '17 at 08:59

kstromeiraos

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Thanks. I was thinking something on that line. I just wanted to confirm it :) – abhishek Jun 20 '17 at 09:07
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see also https://stackoverflow.com/questions/21553353/what-is-the-difference-between-cmd-and-entrypoint-in-a-dockerfile?rq=1 – user2915097 Jun 20 '17 at 09:13
@user2915097 With your permission, I'll add this to my message :) – kstromeiraos Jun 20 '17 at 09:15
suit yourself, no problem :-) – user2915097 Jun 20 '17 at 09:38

What does COMMAND label means in docker container list?

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