How to provide and use command line arguments in docker build?

Question

I have a Dockerfile as shown below:

FROM centos:centos6
MAINTAINER tapash

######  Helpful utils
RUN yum -y install sudo
RUN yum -y install curl
RUN yum -y install unzip

#########Copy hibernate.cfg.xml to Client

ADD ${hibernate_path}/hibernate.cfg.xml /usr/share/tomcat7/webapps/roc_client/WEB-INF/classes/

I need a command line argument to be passed during docker build to be specified for the $hibernate_path.

How do I do this?

Dear negative voter..let me know what's wrong with the question? — Priyanka.Patil
– Priyanka.Patil, Commented Feb 22, 2016 at 11:51
This will not work. The docker file is only read one time, when you build your image. — Rene M.
– Rene M., Commented Feb 22, 2016 at 11:54

VonC · Accepted Answer · 2016-02-23 07:14:56Z

9

If this is purely a build-time variable, you can use the --build-arg option of docker build.

This flag allows you to pass the build-time variables that are accessed like regular environment variables in the RUN instruction of the Dockerfile. Also, these values don’t persist in the intermediate or final images like ENV values do.

docker build --build-arg hibernate_path=/a/path/to/hibernate -t tag .

In 1.7, only the static ENV Dockerfile directive is available.
So one solution is to generate the Dockerfile you need from a template Dockerfile.tpl.

Dockerfile.tpl:

...
ENV hibernate_path=xxx
ADD xxx/hibernate.cfg.xml /usr/share/tomcat7/webapps/roc_client/WEB-INF/classes/
...

Whenever you want to build the image, you generate first the Dockerfile:

sed "s,xxx,${hibernate_path},g" Dockerfile.tpl > Dockerfile

Then you build normally: docker build -t myimage .

You then benefit from (in docker 1.7):

build-time environment substitution
run-time environment variable.

edited Feb 23, 2016 at 7:14

answered Feb 22, 2016 at 13:15

VonC

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17 Comments

Priyanka.Patil Over a year ago

Tried this. Says : flag provided but not defined: --build-arg See 'docker build --help'.

VonC Over a year ago

You must have docker 1.9 or 1.10

Priyanka.Patil Over a year ago

Hm..I'm using docker 1.7. Any options?

VonC Over a year ago

Yes: upgrade. 1.7 is obsolete.

VonC Over a year ago

@Priyanka.Patil ADD is not "runtime". It is build-time. Hence the need of build-arg.

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user2915097 · Accepted Answer · 2016-02-22 12:05:52Z

0

You create a script that puts in your Dockerfile the required value and launches docker build -t mytag .

answered Feb 22, 2016 at 12:05

user2915097

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