fix silently skipped init scripts

[lalyos]

The for loop calling process_init_file in docker-entrypoint.sh silently skips if there are permission issues.

Initializing

the official docs abour initializing-a-fresh-instance instructs to bind mount the /docker-entrypoint-initdb.d/ dir:

docker run \
  -d \
  --name db \
  -e MYSQL_DATABASE=mydb \
  -e MYSQL_ROOT_PASSWORD=secret \
  -v $PWD:/docker-entrypoint-initdb.d/ \
  mysq

the for cycle on a non readable directory (mode 600) silently skips the loop body, leaving the user wonder what's wrong with scripts.

Proposed fix

by adding an extra ls command would produce an error message:

ls: cannot open directory '/docker-entrypoint-initdb.d/': Permission denied

[tianon]

I'm OK with this, but I don't understand the purpose of [ -e /docker-entrypoint-initdb.d/ ], and I'd prefer to send the output of ls to /dev/null (since we only care about it generating a useful error message for us -- we don't actually want the output of ls).

[lalyos]

Hi, @tianon, the purpose of [ -e /docker-entrypoint-initdb.d/ ] is to only try to ls if the directory exists, otherwise every container, which doesn't bind anything to /docker-entrypoint-initdb.d/ would fail.

stdout of ls is redirected to /dev/null

[tianon]

Right, that's what's got me confused -- it'd be pretty unique for someone to not have that directory existing, given that it's created in the base:

mysql/8.0/Dockerfile

Line 23 in 075c24d

RUN mkdir /docker-entrypoint-initdb.d

[tianon]

(And in that case, I think it's totally appropriate for folks to get a harmless ls error.)

[lalyos]

Ohh i see, that makes more sense. I just removed the extra check.

[tianon]

Once Travis is happy again I think we're good to merge. 👍