Simple way to import configuration

[ringerc]

This container is rather handy but I've found it more difficult than I expected to apply a non-default configuration. Specifically I needed to install SSL certificates and keys, apply some postgresql.conf entries and modify pg_hba.conf.

To do so I had to create a setup script in /docker-entrypoint-initdb.d/ to overwrite pg_hba.conf, append to postgresql.conf and copy the SSL certs in from a bind mounted volume. Originally I actually went further and made a derived container that copied these things in before I realised I could just bind mount.

I suggest:

• document that bind-mounting /docker-entrypoint-initdb.d/ is a good way to run scripts and load configuration;
• Special case a /docker-entrypoint-initdb.d/copy-files.d/ directory. When present, copy everything in copy-files.d to the new datadir (recursively, preserving mode and changing ownership to container user). So you can add an include_dir etc.
• Special case a /docker-entrypoint-initdb.d/append-files.d/ directory. When present, append everything in append-files.d to the new datadir with the same filename, creating it if it doesn't exist.
• Auto-append include_dir 'postgresql.conf.d' to the generated postgresql.conf. Document that any config file snippet placed in /docker-entrypoint-initdb.d/copy-files.d/postgresql.conf.d/ will be copied to the datadir and loaded as part of PostgreSQL's configuration. Or alternately just special case postgresql.conf.d in the docker-entrypoint-initdb.d and auto-enable include_dir if it's present.
• Make it more obvious in the docs that scripts in /docker-entrypoint-initdb.d/ run as the postgres user.

[vkukk]

Anything local should be avoided, in cluster it's especially important. Instead of mounting something under /docker-entrypoint-initdb.d/ use docker configs and copy config into that directory.

configs:
  your-config:
    file: ./some_config_script.sh
services:
  postgresql:
    configs:
      - source: your-config
        target: /docker-entrypoint-initdb.d/some_script_name.sh
        uid: 'uid_of_postgresuser'
        mode: 0700

[oshmyrko]

I like the idea to have simple way to import configuration, especially postgresql.conf.d in the docker-entrypoint-initdb.d and auto-enable include_dir if it's present.

And I still cannot understand why include_dir still does not have default value in default postgresql.conf. It would be much easier to import own configs without modifying original one (in order to logically separate them), if there was default value in include_dir.

[marko-asplund]

Anything local should be avoided, in cluster it's especially important. Instead of mounting something under /docker-entrypoint-initdb.d/ use docker configs and copy config into that directory.
...

@vkukk It may not always be possible to use docker-compose.
In those cases customizing server config can be tricky.

[yosifkit]

#835 (comment)

[tianon]

Unfortunately, we're not going to add additional behavior to the image as-is to enable this use case. However, as noted/demonstrated in #835 (comment), it isn't too hard to accomplish with what we do provide. 👍

[ShPakvel]

Unfortunately, we're not going to add additional behavior to the image as-is to enable this use case. However, as noted/demonstrated in #835 (comment), it isn't too hard to accomplish with what we do provide. +1

@tianon It would be nice to provide at least reason(s), why such simple and seems not harmful change to default include_dir = 'conf.d' cannot be provided?
Once again, pros:

• No need to create custom images. Thus no additional space usage and less code.
• It will encourage to stimulate to use best practices described in original documentation. https://www.postgresql.org/docs/13/config-setting.html#CONFIG-INCLUDES

=================
Side remark. On image docs there is wrong information.

From the PostgreSQL docs we see that any option available in a .conf file can be set via -c.

It is actually doesn't work for any "include" type configuration. I suggest to add that information to save time on investigation for other people.