Docker entrypoint and cmd together

Question

I try to setup a Docker with both entrypoint and cmd.

FROM debian:stretch
RUN apt-get update && \
apt install gnupg ca-certificates -y 
RUN echo "deb http://repo.aptly.info/ squeeze main" > /etc/apt/sources.list.d/aptly.list
RUN apt-key adv --keyserver keys.gnupg.net --recv-keys 9E3E53F19C7DE460
RUN apt update && apt install aptly -y
ADD aptly.conf /etc/aptly.conf
ADD start.sh .
VOLUME ["/aptly"]
ENTRYPOINT ["/start.sh"]
CMD ["aptly", "api", "serve"]

But entrypoint script is not stopping... The cmd command is not launching

Here my script :

#!/bin/bash
 set -e 
 init_aptly() { 
 #import pgp key
#create nginx root folder in /aptly
su -c "mkdir -p /aptly/.aptly/public"
echo "12"
 #initialize repository
 #aptly create repo doze-server -   distribution="stable"
  }
  #check for first run
 if [ ! -e /aptly/.aptly/public ]; then
  init_aptly
  echo "13"
 fi
  echo "14"

The script always echo 14, I would like only one and then, execute the cmd command from dockerfile

score 68 · Accepted Answer · answered Dec 05 '17 at 09:19

68

When you use both entrypoint and command, the command section will be appended to entrypoint executable as arguments. Thus in your case:

ENTRYPOINT ["/start.sh"]
CMD ["aptly", "api", "serve"]

Is equivalent to running:

ENTRYPOINT["/start.sh", "aptly", "api", "serve"]

answered Dec 05 '17 at 09:19

yamenk

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87

You can combine executable like bash scripts `CMD ./start.sh && aptly api serve` – yamenk Dec 05 '17 at 12:24
16

This is so intuitive of course.... Strong negative feelings for whoever dev implemented it like so! – George Pligoropoulos Apr 28 '18 at 10:46
3

This ans saved me even in 2019 – rj487 Jun 06 '19 at 22:29
Weird... behavior? – xnervwang May 02 '21 at 04:03
I must be blind but I couldn't seem to see where in the documentation it explains this. Can someone please put a link to the docs showing this? – ADJenks May 27 '22 at 23:00
1

Is there any reason to prefer the first syntax over the second? E.g. could it affect how command overwrite (while running the container) applies? – Marinos An Nov 15 '22 at 14:14
1

@ADJenks Entrypoint example in docker reference (https://docs.docker.com/engine/reference/builder/#exec-form-entrypoint-example) – andy May 05 '23 at 16:16

score 23 · Answer 2 · answered Mar 11 '21 at 23:34

23

One important note, since nobody else has mentioned it: in order to use ENTRYPOINT and CMD together, you need to specify both in the array format. Doing something like this WILL NOT WORK:

ENTRYPOINT ./my_script.sh
CMD echo "hello world"

In the code above, ./my_script.sh will be called, but CMD will not be passed in.

answered Mar 11 '21 at 23:34

Jeremy Blalock

2,538
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3

Thanks, you saved me from hours of debugging! – benjaminchanming Dec 08 '21 at 07:38

Mike Doe · Answer 3 · 2019-10-05T20:19:44.903

6

Can't tell much without knowing what the entrypoint does, but essentially this is what you are doing with this combination of entrypoint and cmd:

/start.sh aptly api serve

If you are after simply starting your server you can simply do something like this (valid path to the aptly executable may be neccessary):

ENTRYPOINT ["aptly"]
CMD ["api", "serve"]

Unless you are doing much more than just running an executable there's no need for an entrypoint.

edited Oct 05 '19 at 20:19

answered Dec 05 '17 at 08:19

Mike Doe

16,349
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1

No need cmd, just ENTRYPOINT [/start.sh aptly api serve]? – Vana Dec 05 '17 at 08:27
Sorry I don't understand your question. – Mike Doe Dec 05 '17 at 09:10

score 1 · Answer 4 · answered Nov 15 '22 at 14:28

The following will allow the default arguments of entrypoint (provided in CMD) to be replaced by the arguments provided in docker run.

ENTRYPOINT ["/start.sh"]
CMD ["aptly", "api", "serve"]

The following will append the arguments provided in docker run to the entrypoint after the last argument. In order to override the entrypoint and its arguments at once you will need to explicitly use the --entrypoint flag:

ENTRYPOINT["/start.sh", "aptly", "api", "serve"]

Docker entrypoint and cmd together

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