Docker + nginx のベースイメージの書き方

Dockerfile

FROM nginx:1.15.12-alpine

# Install gettext 
RUN apk --no-cache add bash libintl perl curl && \
    apk --no-cache add --virtual .build gettext && \
    cp /usr/bin/envsubst /usr/local/bin/envsubst && \
    apk del .build 

ENV NGX_PORT 80
ENV NGX_HOSTNAME _
ENV NGX_LOG_LEVEL warn
ENV NGX_ACCESS_LOG_ENABLED 0 

ADD nginx /etc/nginx/
ADD root /root/

CMD ["sh", "-c", "/root/scripts/docker_start"]

/root/scripts/docker_start

#!/usr/bin/env bash 

# Inject EnvVars
files=`find /etc/nginx -type f -name "*.template"`

for file in $files; do
  envsubst "$(printf '${%s} ' ${!NGX_*})" < $file | tee $file.dist
done

# Replace configured settings
dists=`find /etc/nginx -type f -name "*.template.dist"`
for dist in $dists; do
  mv -v "$dist" "${dist/.template.dist/}";
done

nginx -g "daemon off;"

/etc/nginx/conf.d/default.conf.template

server {
    listen       ${NGX_PORT};
    server_name  ${NGX_HOSTNAME};

    access_log /var/log/nginx/access.log main if=${NGX_ACCESS_LOG_ENABLED};

    # For Healthcheck
    location /_status {
      access_log off;
      return 200 'ok';
    }

    location / {
      root   /usr/share/nginx/html;
      index  index.html index.htm;
    }

    #error_page  404              /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
      root   /usr/share/nginx/html;
    }
}

あとがき

• bashじゃないと ${!NGX_*}とかできないので注意。
• NGX_ じゃなくても大丈夫。
• bash + envsubstが快適