[enhancement] run custom scripts right before service initialization

[acavalin]

Hello,

request

Is it possible to have in /scripts/run.sh a similar mechanism to execute_post_init_scripts function but running just before/after the announce_startup function? 🙏
It could be an execute_pre_init_scripts running all scripts within /docker-pre-init.d/ 🤔

context

I'm using this image in docker swarm and I would like to use docker secrets to pass DKIM keys to the container.

Docker secrets expose your secret values into the running container as files, for example:

# docker_swarm_compose.yml
services:
  mailer:
    image:    boky/postfix
    init:     false # this image uses supervisord init system
    secrets:  [ dkim_public_key, dkim_private_key ]

secrets:
  dkim_public_key:    { file: DKIM_PUBLIC_KEY.txt  }
  dkim_private_key:   { file: DKIM_PRIVATE_KEY.txt }

then in the container you will find these files:

/run/secrets/dkim_public_key
/run/secrets/dkim_private_key

I need to link/copy these files into /etc/opendkim/keys/domain_name.{txt,private} before the initialization scripts, I tried adding a custom script to /docker-init.d/ but it runs too late in /scripts/run.sh 😢

Thank you

[bokysan]

An interesting use case. Generally I don't have issues adding new functionality. What did you have in mind?

Mind you, you can always override your command and do this even before run is executed, e.g. something like:

services:
  mailer:
    volumes:
      - ./override-run.sh:/scripts/override-run.sh
    command: /bin/sh -c /scripts/override-run.sh

And then in override-run.sh put something like:

#!/usr/bin/env sh
ln -s /run/secrets/dkim_public_key /etc/opendkim/keys/domain_name.txt
ln -s /run/secrets/dkim_private_key /etc/opendkim/keys/domain_name.private
exec /scripts/run.sh

[acavalin]

Thank you for the suggestion, I'm currently doing something similar by modifing /script/run.sh:

FROM boky/postfix:latest-debian

RUN set -x \
# copy DKIM keys from secrets at runtime
  && mkdir -p /etc/opendkim/keys \
  && /usr/bin/echo -e \
    "#!/usr/bin/bash                                                      \n" \
    "echo copying DKIM keys from [/run/secrets/] to [/etc/opendkim/keys/] \n" \
    "echo                                                                 \n" \
    "cp /run/secrets/dkim_public_key   /etc/opendkim/keys/xxx.txt         \n" \
    "cp /run/secrets/dkim_private_key  /etc/opendkim/keys/xxx.private     \n" \
    "chmod 644 /etc/opendkim/keys/xxx.txt                                 \n" \
    "chmod 600 /etc/opendkim/keys/xxx.private                             \n" \
    "chown -R opendkim:opendkim /etc/opendkim/keys                                \n" \
    > /copy-dkim-keys.sh \
  && chmod 755 /copy-dkim-keys.sh \
# run /copy-dkim-keys.sh before any other command
  && sed -i -r 's:^#!.+:\0\n\n/copy-dkim-keys.sh\n:' /scripts/run.sh

but I'll switch to your cleaner solution 🙂️

Altought these solutions are something like a hack, I think it's nice to have standardized hooks already baked into the image instead (like execute_post_init_scripts) 😉