Docker COPY sh script not working (not found)

Question

i am not new to docker but i mostly work with prebuilt images, that i connect using docker-compose. I need a super-basic container, that only reads log files and streams the contents to stdout because i have permission issues in another container.

See: https://github.com/webdevops/Dockerfile/issues/332

Anyway - i fail at the very first step and dont know whats the problem

Here is my Dockerfile:

FROM alpine:latest
COPY readlogs.sh /root/readlogs.sh
CMD ['/root/readlogs.sh']

The sheel script looks like this (at the moment - i am testing)

#!/usr/bin/env bash
echo "hello world"

#cat /dev/null > /var/log/app/error.log
#cat /dev/null > /var/log/app/debug.log

#tail -f /var/log/app/error.log > /dev/stderr &
#tail -f /var/log/app/debug.log > /dev/stdout &

As you see i want to truncate some log file and then just read it continously.

Building the image works fine, starting it results in:

/bin/sh: [/root/readlogs.sh]: not found
exited with code 127

NO - the line endings are not DOS.

My docker-compose.yml

  logreader:
    build:
      context: docker/logreader
      dockerfile: Dockerfile
    volumes:
      - ./var/logs:/var/log/app

So - why the funk cant i execute the readlogs.sh file?

The file is executeable (on the host), i tried adding RUN chmod +x /root/readlogs.sh but it did not work either.

Answer 1

For the file not found issue, you need to replace CMD ['/root/readlogs.sh'] for CMD [ "/root/readlogs.sh" ]. Notice the double quotes and the whitespace.

But even after you fix this one, you would still have another issue which is that you're trying to use bash in alpine. So you need to change to sh as Linpy said.