How to detect if the current script is running in a docker build?

user_955091 0
Viewed 785

Suppose I have a Dockerfile which runs a script,

RUN ./myscript.sh

How could I write the myscript.sh so that it could detect if itself is launched by the RUN command during a docker build?

#! /bin/bash

# myscript.sh

if <What should I do here?>
then
  echo "I am in a docker build"
else
  echo "I am not in a docker build"
fi

Ideally, it should not require any changes in the Dockerfile, so that the caller of myscript.sh does not need specialized knowledge about myscript.sh.

dockerfile docker shell linux bash
3 Answers

Try this :

#!/bin/bash

# myscript.sh

isDocker(){
    local cgroup=/proc/1/cgroup
    test -f $cgroup && [[ "$(<$cgroup)" = *:cpuset:/docker/* ]]
}

isDockerBuildkit(){
    local cgroup=/proc/1/cgroup
    test -f $cgroup && [[ "$(<$cgroup)" = *:cpuset:/docker/buildkit/* ]]
}

isDockerContainer(){
    [ -e /.dockerenv ]
}

if isDockerBuildkit || (isDocker && ! isDockerContainer)
then
  echo "I am in a docker build"
else
  echo "I am not in a docker build"
fi
user_21256710

Just to chime in on this, it seems I cannot comment (nor edit as the edit is two characters long... not enough for SO) on the accepted answer but it contains a typo.

the isDockerContainer should read

isDockerContainer(){
    [ -e /.dockerenv ]
}

which created a silent bug in our case.

Cheers

user_180889470

In your Dockerfile, you can try this to run the script

ADD myscript.sh .

RUN chmod +x myscript.sh

ENTRYPOINT ["myscript.sh"]
user_70017490
Related