How do I run a Bash script in an Alpine Docker container?

Question

I have a directory containing only two files, Dockerfile and sayhello.sh:

. ├── Dockerfile └── sayhello.sh 

The Dockerfile reads

FROM alpine COPY sayhello.sh sayhello.sh CMD ["sayhello.sh"] 

and sayhello.sh contains simply

echo hello 

The Dockerfile builds successfully:

kurtpeek@Sophiemaries-MacBook-Pro ~/d/s/trybash> docker build --tag trybash . Sending build context to Docker daemon 3.072 kB Step 1/3 : FROM alpine  ---> 665ffb03bfae Step 2/3 : COPY sayhello.sh sayhello.sh  ---> Using cache  ---> fe41f2497715 Step 3/3 : CMD sayhello.sh  ---> Using cache  ---> dfcc26c78541 Successfully built dfcc26c78541 

However, if I try to run it I get an executable file not found in $PATH error:

kurtpeek@Sophiemaries-MacBook-Pro ~/d/s/trybash> docker run trybash container_linux.go:247: starting container process caused "exec: \"sayhello.sh\": executable file not found in $PATH" docker: Error response from daemon: oci runtime error: container_linux.go:247: starting container process caused "exec: \"sayhello.sh\": executable file not found in $PATH". ERRO[0001] error getting events from daemon: net/http: request canceled 

What is causing this? I recall running scripts in debian:jessie-based images in a similar manner. So perhaps it is Alpine-specific?

Answer 1

Alpine comes with ash as the default shell instead of bash.

So you can

1. Have a shebang defining /bin/bash as the first line of your sayhello.sh, so your file sayhello.sh will begin with bin/sh

   #!/bin/sh 

2. Install Bash in your Alpine image, as you seem to expect Bash is present, with such a line in your Dockerfile:

   RUN apk add --no-cache --upgrade bash 

Answer 2

This answer is completely right and works fine.

There is another way. You can run a Bash script in an Alpine-based Docker container.

You need to change CMD like below:

CMD ["sh", "sayhello.sh"] 

And this works too.