Running Apache 2 under Ubuntu 16.04 on Docker

I recently wanted to setup a new Ubuntu 16.04 host running Apache under Docker for some AWS ECS/Fargate testing I was doing and encountered the following error:

docker run -p 8085:80 aws-ecr-hello-world:v0.5
[Thu Mar 15 00:11:31.074011 2018] [core:warn] [pid 1] AH00111: Config variable ${APACHE_LOCK_DIR} is not defined
[Thu Mar 15 00:11:31.074576 2018] [core:warn] [pid 1] AH00111: Config variable ${APACHE_PID_FILE} is not defined
AH00526: Syntax error on line 74 of /etc/apache2/apache2.conf:
Invalid Mutex directory in argument file:${APACHE_LOCK_DIR}

This is a typical Ubuntu problem where the /etc/apache2/envvars file needs to be sourced before apache2 can start properly. To figure out which ones needed to be added, I commented out the CMD to start apache and instead entered a command to print out the contents of the envvars file. I also added a sed command to print out line 74 of the apache2.conf file so I could further troubleshoot what was happening there.

# Dockerfile
...
CMD ["cat", "/etc/apache2/envvars"]
CMD ["sed", "-n", "74p", "/etc/apache2/apache2.conf"]
...

This output showed that I had to add a few environment variables to the Dockerfile, and verify that they exist when I run the container:

# Dockerfile
...
ENV APACHE_RUN_USER  www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR   /var/log/apache2
ENV APACHE_PID_FILE  /var/run/apache2/apache2.pid
ENV APACHE_RUN_DIR   /var/run/apache2
ENV APACHE_LOCK_DIR  /var/lock/apache2
ENV APACHE_LOG_DIR   /var/log/apache2

RUN mkdir -p $APACHE_RUN_DIR
RUN mkdir -p $APACHE_LOCK_DIR
RUN mkdir -p $APACHE_LOG_DIR
...

I also verified that the directories would exist to prevent any issues there:

# Dockerfile
...
RUN mkdir -p $APACHE_RUN_DIR
RUN mkdir -p $APACHE_LOCK_DIR
RUN mkdir -p $APACHE_LOG_DIR
...

After I finished that, I rebuilt the image and was able to run the container without issues.

The full Dockerfile is:

FROM ubuntu:16.04

# Install dependencies
RUN apt-get update -y
RUN apt-get install -y apache2

# Install apache and write hello world message
RUN echo "Hello World!" > /var/www/index.html

# Configure apache
RUN a2enmod rewrite
RUN chown -R www-data:www-data /var/www


ENV APACHE_RUN_USER  www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR   /var/log/apache2
ENV APACHE_PID_FILE  /var/run/apache2/apache2.pid
ENV APACHE_RUN_DIR   /var/run/apache2
ENV APACHE_LOCK_DIR  /var/lock/apache2
ENV APACHE_LOG_DIR   /var/log/apache2

RUN mkdir -p $APACHE_RUN_DIR
RUN mkdir -p $APACHE_LOCK_DIR
RUN mkdir -p $APACHE_LOG_DIR

EXPOSE 80

# CMD ["sed", "-n", "74p", "/etc/apache2/apache2.conf"]
# CMD ["cat", "/etc/apache2/envvars"]
 CMD ["/usr/sbin/apache2", "-D",  "FOREGROUND"]

Build the container image:

> docker build -t aws-ecr-hello-world:v0.9.1 .
Sending build context to Docker daemon   2.56kB
Step 1/18 : FROM ubuntu:16.04
 ---> f975c5035748
Step 2/18 : RUN apt-get update -y
 ---> Using cache
 ---> 1716ac62d2f6
Step 3/18 : RUN apt-get install -y apache2
 ---> Using cache
 ---> b03c08c103b5
Step 4/18 : RUN echo "Hello World!" > /var/www/index.html
 ---> Using cache
 ---> a8352375b937
Step 5/18 : RUN a2enmod rewrite
 ---> Using cache
 ---> 313f2e8046ec
Step 6/18 : RUN chown -R www-data:www-data /var/www
 ---> Using cache
 ---> c2e7512d4fe8
Step 7/18 : ENV APACHE_RUN_USER  www-data
 ---> Using cache
 ---> 2054c48681ae
Step 8/18 : ENV APACHE_RUN_GROUP www-data
 ---> Using cache
 ---> 493b20667534
Step 9/18 : ENV APACHE_LOG_DIR   /var/log/apache2
 ---> Using cache
 ---> 8c5029eb8e83
Step 10/18 : ENV APACHE_PID_FILE  /var/run/apache2/apache2.pid
 ---> Using cache
 ---> 701ddcccf335
Step 11/18 : ENV APACHE_RUN_DIR   /var/run/apache2
 ---> Using cache
 ---> 6700b8a02ca0
Step 12/18 : ENV APACHE_LOCK_DIR  /var/lock/apache2
 ---> Using cache
 ---> ac692e86caf7
Step 13/18 : ENV APACHE_LOG_DIR   /var/log/apache2
 ---> Using cache
 ---> 660af37232bc
Step 14/18 : RUN mkdir -p $APACHE_RUN_DIR
 ---> Running in 02978786f1b5
Removing intermediate container 02978786f1b5
 ---> 3e5ef0c00431
Step 15/18 : RUN mkdir -p $APACHE_LOCK_DIR
 ---> Running in 68408f3091c1
Removing intermediate container 68408f3091c1
 ---> 90efa3a2f9bc
Step 16/18 : RUN mkdir -p $APACHE_LOG_DIR
 ---> Running in f1ee7e4d5a4b
Removing intermediate container f1ee7e4d5a4b
 ---> 9fb6a50c6792
Step 17/18 : EXPOSE 80
 ---> Running in f3fd904326e4
Removing intermediate container f3fd904326e4
 ---> b4ba8575620d
Step 18/18 : CMD ["/usr/sbin/apache2", "-D",  "FOREGROUND"]
 ---> Running in a3cba653d7b3
Removing intermediate container a3cba653d7b3
 ---> 0bfa187abf69
Successfully built 0bfa187abf69
Successfully tagged aws-ecr-hello-world:v0.9.1

Run the container:

> docker run -p 8085:80 aws-ecr-hello-world:v0.9.1
AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message

UPDATE: it looks like James Turnbull had already solved this problem here.