Dockerfile demonstrating (probably) a bug in Docker (in 0.7 and I think in 0.6.5).

boom.sh

#! /bin/bash
echo Before scp.
scp a scp@172.17.0.19:b
echo After scp.

while [ true ] ; do
    echo "Now looping (which is good)."
    sleep 1
done

Dockerfile

from ubuntu:12.04
maintainer Vo Minh Thu <noteed@gmail.com>

run echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
run apt-get update

# Install PostgreSQL (for the postgres user)
run apt-get install -q -y postgresql-9.1

# Install OpenSSH (for scp)
run apt-get install -q -y openssh-client

# When run, this should loop endlessly, but does not, which is the problem being demonstrated.
add boom.sh /usr/bin/boom.sh

cmd ["/bin/su", "postgres", "-c", "boom.sh"]