Docker: Error code 127 when executing shell script - docker

Question

So I can't seem to figure this out, but I'm getting error code 127 when running a Dockerfile. What causes this error?
My Dockerfile:
FROM composer as comp
FROM php:7.4-fpm-alpine
COPY --from=comp /usr/bin/composer /usr/bin/composer
COPY ./docker/install-deps.sh /tmp/install-deps.sh
RUN echo $(ls /tmp)
RUN /tmp/install-deps.sh
COPY . /var/www
WORKDIR /var/www
RUN composer install -o --no-dev
The results after building the Dockerfile:
Building php
Step 1/9 : FROM composer as comp
---> 433420023b60
Step 2/9 : FROM php:7.4-fpm-alpine
---> 78e945602ecc
Step 3/9 : COPY --from=comp /usr/bin/composer /usr/bin/composer
---> 46117e22b4de
Step 4/9 : COPY ./docker/install-deps.sh /tmp/install-deps.sh
---> 7e46a2ee759c
Step 5/9 : RUN echo $(ls /tmp)
---> Running in aa1f900032f9
install-deps.sh
Removing intermediate container aa1f900032f9
---> eb455e78b7f6
Step 6/9 : RUN /tmp/install-deps.sh
---> Running in 6402a15cccb2
/bin/sh: /tmp/install-deps.sh: not found
ERROR: Service 'php' failed to build: The command '/bin/sh -c /tmp/install-deps.sh' returned a non-zero code: 127
The install-deps.sh:
#!/bin/sh
set -e
apk add --update --no-cache \
postgresql-dev \
mysql-client \
yaml-dev \
git \
openssl
docker-php-ext-install pcntl pdo_mysql pdo_pgsql
# yaml
apk add --no-cache --virtual .build-deps g++ make autoconf
pecl channel-update pecl.php.net
pecl install yaml
docker-php-ext-enable yaml
apk del --purge .build-deps

Answer 1

Docker is executing the install-deps.sh script. The issue is with a command inside install-deps.sh that is not recognized when docker attempts to run the script.
As you can see the script returns an error code of 127 meaning that a command within the file does not exist.
For instance - try this:
touch test.sh
echo "not-a-command" >> test.sh
chmod 755 test.sh
/bin/sh -c "./test.sh"
Output:
/root/test.sh: line 1: not-a-command: command not found
Now check the exit code:
echo $?
127
I would suggest running the script inside an interactive environment to identify/install the command that is not found.