Debian Working System for Docker
This is a simple set of images that transform the standard Docker
Debian environment into one that provides more traditional full
Unix APIs (including syslog, zombie process collection, etc.)
Despite this, they are all very small, both in terms of disk and RAM usage.
You can find a description of the motivation for these images on my blog.
This is loosely based on the concepts, but not the code, in the
You can look at that link for additional discussion on the motivations.
This image uses sysvinit instead of systemd, not because of any
particular opinion on the merits of them, but rather because
sysvinit does not require any kind of privileged Docker
or cgroups access.
Here are the images I provide from this repository:
- jgoerzen/debian-base-minimal - a minimalistic base for you.
- Provides working sysvinit, syslogd, cron, anacron, at, and logrotate.
- syslogd is configured to output to the docker log system by default.
- jgoerzen/debian-base-standard - adds some utilities. Containes everything above, plus:
- Utilities: less, nano, vim-tiny, man-db (for viewing manpages), net-tools, wget, curl, pwgen, zip, unzip
- Email: exim4-daemon-light, mailx
- Network: netcat-openbsd, socat, openssl, ssh, telnet (client)
- jgoerzen/debian-base-security - A great way to keep thins updated. Contains everything above, plus:
- automated security patches using unattended-upgrades and needrestart
- jgoerzen/debian-base-vnc - For systems that need X. debian-base-security, plus:
- tightvncserver, xfonts-base, lwm, xterm, xdotool, xvnc4viewer
- jgoerzen/debian-base-apache - A web server - debian-base-security, plus:
- apache2 plus utilities: ssl-cert
- LetsEncrypt options: certbot, acme-tiny
- jgoerzen/debian-base-apache-php - debian-base-apache, plus:
- libapache2-mod-php (mod-php5 on jessie)
Memory usage at boot (stretch):
- jgoerzen/debian-base-minimal: 6MB
- jgoerzen/debian-base-standard: 11MB
- jgoerzen/debian-base-security: 11MB
These images are autobuilt for jessie, stretch, and sid.
You can install with:
docker pull jgoerzen/debian-base-whatever
Your Dockerfile should use CMD to run
When running, use
-t to enable the logging to
This environment variable is available for your use:
stdout, which redirects all syslog activity
to the Docker infrastructure. If you instead set it to
internal, it will
use the default Debian configuration of logging to
container. The configuration is applied at container start time by
/etc/syslog.confsymlink to point to either
syslog.conf.internalis the default from the system.
dpkg-divertis used to force all packages' attempts to write to
to instead write to
DEBBASE_TIMEZONE, if set, will configure the
files in the container to the appropriate timezone.
disabled. If you set to
enabled, then the SSH server
will be run.
Executables or scripts may be placed in
/usr/local/preinit, which will be executed
at container start time by
run-parts prior to starting init. These can
therefore perform container startup steps. A script which needs to only run
once can delete itself after a successful run to prevent a future execution.
You can cause
docker stop to invoke an orderly shutdown by running the container
docker run -td --stop-signal=SIGPWR --name=name jgoerzen/debian-base-whatever
If you don't start it this way, you can instead use these steps:
docker kill -s SIGPWR container sleep 10 docker kill container
Within the container, you can call
telinit 1 to cause the container to shutdown.
Orderly Shutdown Mechanics
docker stop sends the SIGTERM (and, later, SIGKILL) signal to PID
1 (init) iniside a container. sysvinit does not act upon this signal.
This will shut down a container, but it will not give your shutdown scripts
the chance to run gracefully. In many situations, this is fine, but it may
not be so in all.
A workaround is, howerver, readily available, without modifying init. These
images are configured to perform a graceful shutdown upon receiving
The process for this is... interesting, since we are unable to directly
kill PID 1 inside a docker container. First, init calls
The powerfail script I install simply tells init to go to single-user mode.
This causes it to perform an orderly shutdown of the daemons, and when it is
done, it invokes
/sbin/sulogin. On an ordinary system, this prompts for
the root password for single-user mode. In this environment, we instead
symlink /sbin/init to /bin/true, then tell init to re-exec itself. This
causes PID 1 to finally exit.
One of the preinit scripts makes sure that
/sbin/init properly links to
/sbin/init.real at boot time.
Although the standard and security images run the SMTP and SSH servers,
they do not expose these to the Internet by default. Both require
site-specific configuration before they are actually useful.
Because the SMTP service is used inside containers, but the SSH service
generally is not, the SSH service is disabled by default.
Enabling or Disabling Services
You can enable or disable services using commands like this:
update-rc.d ssh disable
update-rc.d ssh enable
email is the main thing you'd need to configure. In the running system,
dpkg-reconfigure -plow exim4-config will let you do this.
SSH host keys will be generated upon first run of a container, if
they do not already exist. This implies every instantiation
of a container containing SSH will have a new random host key.
If you want to override this, you can of course supply your own
files in /etc/ssh or make it a volume.
These tags are pushed:
- latest, stretch: Debian stretch
- jessie: Debian jessie
- sid: Debian sid (not tested)
Docker scripts, etc. are
Copyright (c) 2017 John Goerzen
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