pyraf-docker

Docker image for running pyraf.

Docker

To build and push a new image:

$ docker build -t huitacademictechnology/pyraf .
$ docker run --rm -it huitacademictechnology/pyraf:latest /bin/bash -c "pyraf --version"
$ docker login
$ docker push huitacademictechnology/pyraf

To run pyraf and use X apps, follow the instructions below.

X Window System

Background

The Linux graphical windowing system is called X11, also known as X Windows, or X for short. X forwarding is a feature of X where a graphical program runs on one computer, but the user interacts with it on another computer. If you've ever used Remote Desktop, it's conceptually like that, but it works on a program-by-program or window-by-window basis.

Installation

For Mac OS X, install XQuartz.

Configuration

1. Ensure that you have an ~/.Xauthority file (a binary file used to authorize connections to the DISPLAY):

   $ touch ~/.Xauthority
   

2. Add XAuthLocation to ~/.ssh/config:

   XAuthLocation /opt/X11/bin/xauth
   

   This is so that ssh knows where to find the xauth program that is provided by XQuartz, since it's in a non-standard location.
3. Add ForwardX11Timeout to ~/.ssh/config:

   ForwardX11Timeout 10h
   

   This increases the default timeout from 20min to 10hrs. Note that this only applies if ForwardX11Trusted no (e.g. ssh -X instead of ssh -Y).

DISPLAY and Xauthority

The most important environment variable for X is $DISPLAY. This will be set by your X server (e.g. XQuartz) and defines a value in the following format: hostname:D.S.

• hostname is the name of the computer the X server runs on (localhost if omitted).
• D is a sequence number if there are multiple displays.
• S is a screen number (typically 0 because there's one secreen)

The .Xauthority file is used to authorize cookie-based access to the $DISPLAY. It defines a "magic cookie" that must be presented by X clients when connecting to the X display server.

Since this is a binary file, you can't view it directly, but must use the xauth command:

$ echo $DISPLAY
$ xauth list

See also:

• https://en.wikipedia.org/wiki/X_Window_authorization
• https://datacadamia.com/ssh/x11/display

Running the docker image on Mac OS X

Assumes you have Docker Desktop for Mac and you want to run the docker image locally.

1. Install socat:

   $ brew install socat
   

2. Launch XQuartz

   $ open -a XQuartz
   

3. Go to the XQuartz security tab and ensure Allow connections from network clients is checked.
4. Use socat to forward traffic from port 6000 to the unix display socket:

   $ socat TCP-LISTEN:6000,reuseaddr,fork UNIX-CLIENT:\"$DISPLAY\"
   $ lsof -i TCP:6000 # verify socat is listening
   

5. Start docker:

   $ docker pull huitacademictechnology/pyraf:latest
   $ docker run --rm -e DISPLAY=docker.for.mac.host.internal:0 -it huitacademictechnology/pyraf:latest /bin/tcsh
   

6. Run an X11 app such as xterm or xeyes

   $ xterm &
   

   If successful, you should see an xterm open on your desktop.
7. Run pyraf:

   $ pyraf
   

Running the docker image on a remote EC2

Assumes you have an Ubuntu EC2 instance with Docker Engine installed and you want to run the docker image remotely, but interact with it locally on your desktop.

1. Launch XQuartz

   $ open -a XQuartz
   

2. Connect to the EC2 with X Forwarding enabled:

   $ ssh -X ubuntu@<IP>
   $ touch ~/.Xauthority
   

3. Start docker:

   $ docker pull huitacademictechnology/pyraf:latest
   $ docker run --rm -e DISPLAY --network host -v "$HOME/.Xauthority:/root/.Xauthority:rw" -it huitacademictechnology/pyraf:latest /bin/tcsh
   

4. Run an X11 app such as xterm or xeyes

   $ xterm &
   

   If successful, you should see an xterm open on your desktop.
5. Run pyraf:

   $ pyraf
   

Note: The X client within the docker container must be able to find the X server specified in the $DISPLAY. By setting the docker network to host instead of bridge, it will be able to easily resolve the hostname and connect to the X server (which in this case is SSHD proxying the request back to your computer). Note that this technique is not recommended for deployment, just for testing.