[zaroth]

A large part of the document boils down to 'run with defaults', 'setup auditing', and 'check file permissions', 'drop unneeded capabilities', 'define sane limits', 'centralize and rotate logs', and 'make backups'. These are all really great baseline steps. There were also I think a few Docker-specific points worth highlighting;

- Run with -icc=false. This should have been the default but isn't for legacy reasons I think. By default there is no firewall between containers. icc=false turns the inter-container firewall on. This is a pretty basic one, but easy for new docker users to miss.

- Host port mapping (e.g. -p 80) by default binds to 0.0.0.0:80 on the host container. This could inadvertently expose your internal services to unexpected interfaces. Specify the host IP you want to bind to explicitly (e.g. -p 127.0.0.1:49123:8080)

- Run inside containers as non-root. Most Dockerfiles you come across will run as root inside the container. In your base image, 'RUN useradd' and in your Dockerfiles add a 'USER' directive, and start the container with -u <user>.

- Set root file system as read-only inside the container. It enforces the best practice that the container should be immutable anyway.

- Instead of --restart:always, try --restart=on-failure:5 to avoid a possible DoS or excessive flapping. Not sure if I 100% agree with this, but it's an interesting suggestion.

[general_failure]

I have never managed the readonly container to work.

/var/run needs to be writable. /tmp needs to be writable and so on. I gave it a shot again today:

$ docker run --read-only=true -ti ubuntu:14.10 touch /tmp/foo

touch: cannot touch '/tmp/foo': Read-only file system

How is this supposed to work? There is little to no information on how this feature works. Can you give me a pointer?

In addition, restart:on-failure appears to have issues if docker itself crashes.

[kentonv]

Once inside the container, you need to mount a tmpfs at /tmp, and another one at /run (which /var/run usually links to).

E.g.:

    mount -t tmpfs -o size=256M tmpfs /tmp

(I'm not sure if/how you can make Docker do this automatically. I'd imagine there's a flag or something.)

[doomrobo]

You could use the CMD keyword in the Dockerfile to ensure that that's run every time the container is started

[steilpass]

> - Run with -icc=false. This should have been the default +1

But I would add: not just form a security perspective but also from a architecture perspective to enforce encapsulation.

Have been wondering about this too: http://stackoverflow.com/questions/29952937/why-is-inter-con...

[dordoka]

Regarding the -icc=false option, if you want to do it by default to all containers, just modify the docker daemon's options adding --iptables=false [0] and restart the daemon.

[0] https://docs.docker.com/articles/networking/#between-contain...