pip install git+https://github.com/larsks/dockerize

usage: dockerize [-h] [--tag TAG] [--cmd CMD] [--entrypoint ENTRYPOINT]
                 [--no-build] [--output-dir OUTPUT_DIR] [--add-file SRC DST]
                 [--symlinks SYMLINKS] [--user USER] [--group GROUP]
                 [--filetools] [--verbose] [--debug] [--version]
                 ...
positional arguments:
  paths
optional arguments:
  -h, --help            show this help message and exit
  --add-file SRC DST, -a SRC DST
                        Add file <src> to image at <dst>
  --symlinks SYMLINKS, -L SYMLINKS
                        One of preserve, copy-unsafe, skip-unsafe, copy-all
  --user USER, -u USER  Add user to /etc/passwd in image
  --group GROUP, -g GROUP
                        Add group to /etc/group in image
  --filetools           Add common file manipulation tools
  --version             show program's version number and exit
Docker options:
  --tag TAG, -t TAG     Tag to apply to Docker image
  --cmd CMD, -c CMD
  --entrypoint ENTRYPOINT, -e ENTRYPOINT
Output options:
  --no-build, -n        Do not build Docker image
  --output-dir OUTPUT_DIR, -o OUTPUT_DIR
Logging options:
  --verbose
  --debug

dockerize -t sed /bin/sed

$ echo hello world | docker run -i sed s/world/jupiter
hello jupiter

dockerize -t thttpd \
  -a /var/www/thttpd /var/www \
  --entrypoint '/usr/sbin/thttpd -D' \
  --cmd '-d /var/www' \
  /usr/sbin/thttpd

docker run thttpd

docker run -v /my/content:/var/www thttpd