Convert explicit "export A=B" lines of Apache's envvars file into "${A:=B}" such that we can override them at runtime easily

[tianon]

This is intended as something to think about and discuss first, which is why I've not run update.sh yet. 😄

The intended use case is to allow for these pre-provided environment variables which are currently hard-coded and can only be changed by modifying this envvars file to be easily user-specifiable via -e on the docker run command line.

Before:

unset HOME

if [ "${APACHE_CONFDIR##/etc/apache2-}" != "${APACHE_CONFDIR}" ] ; then
    SUFFIX="-${APACHE_CONFDIR##/etc/apache2-}"
else
    SUFFIX=
fi

export APACHE_RUN_USER=www-data
export APACHE_RUN_GROUP=www-data
export APACHE_PID_FILE=/var/run/apache2/apache2$SUFFIX.pid
export APACHE_RUN_DIR=/var/run/apache2$SUFFIX
export APACHE_LOCK_DIR=/var/lock/apache2$SUFFIX
export APACHE_LOG_DIR=/var/log/apache2$SUFFIX

export LANG=C

export LANG

After:

unset HOME

if [ "${APACHE_CONFDIR##/etc/apache2-}" != "${APACHE_CONFDIR}" ] ; then
    SUFFIX="-${APACHE_CONFDIR##/etc/apache2-}"
else
    SUFFIX=
fi

: ${APACHE_RUN_USER:=www-data}
export APACHE_RUN_USER
: ${APACHE_RUN_GROUP:=www-data}
export APACHE_RUN_GROUP
: ${APACHE_PID_FILE:=/var/run/apache2/apache2$SUFFIX.pid}
export APACHE_PID_FILE
: ${APACHE_RUN_DIR:=/var/run/apache2$SUFFIX}
export APACHE_RUN_DIR
: ${APACHE_LOCK_DIR:=/var/lock/apache2$SUFFIX}
export APACHE_LOCK_DIR
: ${APACHE_LOG_DIR:=/var/log/apache2$SUFFIX}
export APACHE_LOG_DIR

: ${LANG:=C}
export LANG

export LANG

(minus comments)

Fixes #14

[tianon]

The main thing I see this breaking is folks who are using sed on this file themselves, but I did do a search of GitHub for Dockerfiles mentioning /etc/apache2/envvars and came up pretty near empty as far as anyone actually doing that in a major way. (Which isn't to say nobody is, but it does mean it's probably not a normal practice -- most folks I saw were just replacing the file outright or sourcing it for other reasons.)

[tianon]

This has fun implications for issues like #14 too. 😄 (To be clear, by "fun", I mean "likely fixes the issue".)

[yosifkit]

👍, though I kind of wish something like document root was in there too, so we could solve some other issues.

[tianon]

Yeah, I think that's something we could consider adding pretty easily as a "next step" following this, if we decide it makes sense. Should be pretty easy to implement. 👍

(I've just pushed a commit applying update.sh changes.)

[yosifkit]

LGTM

[Vampouille]

This has fun implications for issues like #14 too. (To be clear, by "fun", I mean "likely fixes the issue".)

@tianon, I think #14 is about changing UID at runtime by environment variables. With this PR, we can only change apache user at build time and we need to extend image with creation of such user.

So can you reopen #14 ?

[tianon]

@Vampouille it used to be build-time only, but this PR makes it possible to set variables like APACHE_RUN_USER at runtime -- the current issue with using it is that it hasn't made it over to https://github.com/docker-library/official-images yet