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

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.

Remember to grant execution permission for all scripts.

FROM alpine
COPY sayhello.sh /sayhello.sh
RUN chmod +x /sayhello.sh
CMD ["/sayhello.sh"]

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

So you can

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
```
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
```

By using the CMD, Docker is searching the sayhello.sh file in the PATH, BUT you copied it in / which is not in the PATH.

So use an absolute path to the script you want to execute:

CMD ["/sayhello.sh"]

BTW, as @user2915097 said, be careful that Alpine doesn't have Bash by default in case of your script using it in the shebang.

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