dockerfile 中有一句：

COPY supervisord.conf /etc/supervisord.conf

构建成功，但是进入容器却找不到这个文件，为什么？

另外，这个容器为什么不能用 docker-compose exec php-worker bash 进入，而要用 docker-compose exec php-worker sh？

完整的 dockerfile 如下：

#
#--------------------------------------------------------------------------
# Image Setup
#--------------------------------------------------------------------------
#

FROM php:7.1-alpine

MAINTAINER Mahmoud Zalt <mahmoud@zalt.me>

RUN apk --update add wget \
  curl \
  git \
  build-base \
  libmemcached-dev \
  libmcrypt-dev \
  libxml2-dev \
  zlib-dev \
  autoconf \
  cyrus-sasl-dev \
  libgsasl-dev \
  supervisor

RUN docker-php-ext-install mysqli mbstring pdo pdo_mysql mcrypt tokenizer xml
RUN pecl channel-update pecl.php.net && pecl install memcached-3.0.4 && docker-php-ext-enable memcached

# Install PostgreSQL drivers:
ARG INSTALL_PGSQL=false
RUN if [ ${INSTALL_PGSQL} = true ]; then \
    apk --update add postgresql-dev \
        && docker-php-ext-install pdo_pgsql \
;fi

RUN rm /var/cache/apk/* \
    && mkdir -p /var/www

#
#--------------------------------------------------------------------------
# Optional Supervisord Configuration
#--------------------------------------------------------------------------
#
# Modify the ./supervisor.conf file to match your App's requirements.
# Make sure you rebuild your container with every change.
#

COPY supervisord.conf /etc/supervisord.conf

ENTRYPOINT ["/usr/bin/supervisord", "-n", "-c",  "/etc/supervisord.conf"]

#
#--------------------------------------------------------------------------
# Optional Software's Installation
#--------------------------------------------------------------------------
#
# If you need to modify this image, feel free to do it right here.
#
    # -- Your awesome modifications go here -- #


#
#--------------------------------------------------------------------------
# Final Touch
#--------------------------------------------------------------------------
#

WORKDIR /etc/supervisor/conf.d/