How to add EnvironmentFile directive to systemctl using Docker with centos7/httpd base image - apache

Question

I am not sure if this is possible without creating my own base image, but I use environment variables in /etc/environment on our servers and typically make them accessible to apache by doing the following:
$ printf "HTTP_VAR1=var1-value\n\
HTTP_VAR2=var2-value"\
>> /etc/environment
$ mkdir /usr/lib/systemd/system/httpd.service.d
$ printf "[Service]\n\
EnvironmentFile=/etc/environment"\
> /usr/lib/systemd/system/httpd.service.d/environment.conf
$ systemctl daemon-reload
$ systemctl restart httpd
$ reboot
The variables are then available in any PHP calls to getenv('HTTP_VAR1'); and etc. However, in running this from a docker file I get dbus errors on the systemctl commands. Without the systemctl commands it seems the variables are not available to apache as it seems the new EnvironmentFile directive doesn't take effect. My docker file snippet:
FROM centos/httpd:latest
RUN printf "HTTP_VAR1=var1-value\n\
HTTP_VAR2=var2-value"\
>> /etc/environment
RUN mkdir /usr/lib/systemd/system/httpd.service.d &&\
printf "[Service]\n\
EnvironmentFile=/etc/environment"\
> /usr/lib/systemd/system/httpd.service.d/environment.conf
RUN systemctl daemon-reload &&\
systemctl restart httpd
COPY entrypoint.sh /entrypoint.sh

Answer 1

So I happened upon the answer to the issue today. It seems that systemd drops backslashes inside single quotes, but it may effect double-quotes too from what I saw in testing. I found the systemd development mailing list thread from April 2014 where patching the issue was being discussed. It seems as though the fix never made it in. So we have to work around it.
In attempting to work around it I noticed some issues with actually reading the variables at all. It seemed as though either Apache or php-cli would get the correct variables, and sometimes not at all, it took a bit of sleuthing to figure out what was going on. Then I started reading into the systemd's EnvironmentFile directive to see if there was more to gain from the docs. It turns out it does not evaluate bash so export won't work. It expects a text file with variable assignments and herein lies one of the main issues that might keep this from being resolved.
I then devised a workable solution. Utilizing systemd's ExecStartPre directive I am able to run a script on startup of the httpd service. I then read in the environment file and write a new plain text one that will then be used by httpd's systemd unit. Here is the code:
Firstly, I moved my variables to /etc/profile.d/ directory rather than /etc/environment file.
file: /etc/profile.d/environment.sh
This is where we store all our environment variables, this gets easily sourced on all interactive shell logins. In the rarer cases where we need to have these variables available non-interactively we can either provide --login flag to /bin/bash or source it manually.
export HTTP_VAR1=var1-value-with-a-back\slash
export HTTP_VAR2=var2-value
file: /usr/lib/systemd/system/httpd.service.d/environment.conf
Our drop-in unit file to extend how the httpd service works. I add in a script that runs before httpd starts up. This gets ran on all httpd restarts and starts. The script that runs generates a plain text file at /etc/profile.d/environment.env which we subsequently tell systemd to load as an EnvironmentFile.
[Service]
ExecStartPre=/usr/bin/bash -c "/usr/local/bin/generate-plain-environment-file"
EnvironmentFile=/etc/profile.d/environment.env
file: /usr/local/bin/generate-plain-environment-file
Here is the script I am using, I whipped this together really fast, I really don't think it is that robust and it could be better. It just removes the export from the beginning of the lines and then escapes any backslashes since systemd drops single backslashes. A more proper solution might be to use bash to evaluate each line and obtain the variable value in case of usage of variables or other bash in the actual bash variables, then output them as plain text name=value assignments, however this is not part of my use-case so I didn't bother.
#!/bin/bash
cd /etc/profile.d/
rm -rf "./environment.env"
while IFS='' read -r line || [[ -n "$line" ]]; do
echo $(echo "${line}" | sed 's/^export //' | sed 's/\\/\\\\/g') >> "./environment.env";
done < "./environment.sh"
file: /etc/profile.d/environment.env
This is the resulting file generated by the described script.
HTTP_VAR1=var1-value-with-a-back\\slash
HTTP_VAR2=var2-value
Conclusion is that the I now have two files with the same thing in them but I only need to maintain the one, the other is generated each time we restart httpd. Also, we fix the backslash issue in the process. Hurray!