webdevops/base¶
Our application base container contains some general tools, the provisioning system (Ansible), a preconfgured
modular supervisord and a modular entrypoint script.
Uses Supervisord
This image is using supervisor and runs the daemon under user application (UID 1000; GID 1000) as default. If the container is
started under a different user the daemon will be run under the specified uid.
Docker image tags¶
| Tag | Distribution name |
|---|---|
alpine |
Alpine |
alpine-3 |
deprecated |
ubuntu-12.04 |
deprecated |
ubuntu-14.04 |
deprecated |
ubuntu-15.04 |
deprecated |
ubuntu-15.10 |
deprecated |
ubuntu-16.04 |
deprecated |
debian-7 |
deprecated |
debian-8 |
deprecated |
debian-9 |
deprecated |
centos-7 |
Environment variables¶
Base environment variables¶
| Environment variable | Description | Default |
|---|---|---|
LOG_STDOUT |
Destination of daemon output | empty (stdout) |
LOG_STDERR |
Destination of daemon errors | empty (stdout) |
SERVICE_CRON_OPTS |
cron daemon arguments | empty (when syslog is used) |
SERVICE_DNSMASQ_OPTS |
dnsmasq daemon arguments | empty (when syslog is used) |
SERVICE_DNSMASQ_USER |
dnsmasq effective user | root |
SERVICE_POSTFIX_OPTS |
postfix daemon arguments | empty (when syslog is used) |
SERVICE_SSH_OPTS |
ssh daemon arguments | empty (when syslog is used) |
SERVICE_SUPERVISOR_OPTS |
supervisor daemon arguments | empty (when syslog is used) |
SERVICE_SUPERVISOR_USER |
supervisor effective user | root |
SERVICE_SYSLOG_OPTS |
syslog daemon arguments | empty (when syslog is used) |
Entrypoint¶
The entrypoint script is located in /opt/docker/bin/entrypoint.sh and will also start the entrypoint provisioning
before running the requested CMD.
Based on CMD the entrypoint script is trying to find the appropriate worker script located in
/opt/docker/bin/entrypoint.d and executes it. It must matches the CMD and if there is no appropriate
worker script the entrypoint falls back to /opt/docker/bin/entrypoint.d/default.sh which just executes
the specified CMD.
This approach allows a modular entrypoint and also allows to directly jump into a container
(eg. with docker run -ti webdevops/apache bash) without uploading or modifing the entrypoint.
Example for starting supervisord (executed by entrypoint.d/supervisord.sh):
ENTRYPOINT ["/opt/docker/bin/entrypoint.sh"]
CMD ["supervisord"]
| File/Directory | Description |
/opt/docker/bin/entrypoint.sh |
Entrypoint script for ENTRYPOINT instruction in Dockerfile |
/opt/docker/bin/entrypoint.d/default.sh |
Default worker script, will execute the defined cmd |
/opt/docker/bin/entrypoint.d/cli.sh |
Starts predefined CLI_SCRIPT (environment variable) |
/opt/docker/bin/entrypoint.d/noop.sh |
Starts a noop endless loop at startup |
/opt/docker/bin/entrypoint.d/root.sh |
Starts a root shell (deprecated) |
/opt/docker/bin/entrypoint.d/supervisord.sh |
Starts supervisord daemon at startup (CMD ["supervisord"]) |
Supervisord¶
Supervisord is a lightweight daemon which starts and monitor other programs. We’re using it for running more than one task in a docker container (eg. PHP-FPM and Apache/Nginx).
| File/Directory | Description |
/opt/docker/etc/supervisor.conf |
Main supervisord configuration file |
/opt/docker/etc/supervisor.d/*.conf |
Modular service configuration files for supervisord (will be included automatically) |
/opt/docker/bin/servide.d/*.sh |
Service scripts if services needs more than just a single command line for startup |
Provisioning¶
With Ansible the provisioning tasks can be easliy done inside the Docker image (eg. for configurations and deployments). There is also a small provision script for registring and running Ansible roles.
For even simpler tasks there is also a possibility to upload small shell scripts which will be executed at the specific tags.
Register a new role (eg. with tag build): /opt/docker/bin/provision add --tag build rolename
Run all registred roles and scripts (in Dockerfile): /opt/docker/bin/bootstrap.sh
| Tag | Description |
bootstrap |
Run on Docker image creation (only run once) |
build |
Run on Docker image build |
onbuild |
Run on Docker image ONBUILD |
entrypoint |
Run on Docker image entrypoint execution (only here Environment variables are available) |
| File/Directory | Description |
/opt/docker/bin/provision |
Provision script |
/opt/docker/bin/bootstrap.sh |
Wrapper for running registred provisions (just run it as last script in Dockerfile) |
/opt/docker/provision/roles |
Directory for Ansible roles |
/opt/docker/provision/bootstrap.d/*.sh |
Directory for provisioning shell scripts (tag: bootstrap) |
/opt/docker/provision/build.d/*.sh |
Directory for provisioning shell scripts (tag: build) |
/opt/docker/provision/onbuild.d/*.sh |
Directory for provisioning shell scripts (tag: onbuild) |
/opt/docker/provision/entrypoint.d/*.sh |
Directory for provisioning shell scripts (tag: entrypoint) |