Friday, 28 October 2016

Administrator : Using Python to Serve Files (HTTP)

The second in my mini-series of how to share storage between machines, easily, we're going to look at using Python as a Simple HTTP Server...

On Linux, with at least Python version 2.15.x (use "python --version" to check) you can simply run:

python -m SimpleHTTPServer

And the current folder will be served up on the primary ethernet controller on port 8080.

This is extremely useful to let some remote machine pull files quickly off of a system, and it's a very good technique to remember when you're developing and deploying, because you can just host your "/bin/debug" or "/bin/release" directory to the remote system, and when your builds complete that remote side can pull the new files or images over.

To do the fulling on Linux, I prefer to use wget, so lets assume the above folder is "/home/xelous/share" inside it is a file: "hello.txt", and the IP is, this is the wget from the remote machine:


And voila, the file is whisked as a HTTP download across to the remote machine's current folder.

You can write scripts to pull lots of files over and then do builds, use a makefile and you can do builds from your code quickly as you carry on working, this is very useful in my set up as I have an 8 core laptop I can use to kick builds off on, whilst my local workstation can carry on doing another build.  When you're producing ARM kernel builds for two different platforms at the same time molding this simple server and wget to your whim streamlines your development speed so so much!

On windows you have to have a command prompt with the path to python set, lets assume our python is installed in "C:\Python":


Then start the server from the "web" folder:

cd \web
python -m http.server 8080

This does exactly the same as the linux version, except now we're hosted on Windows, and sharing the "C:\Web" folder on our server.

You can browse straight to both of these servers and just see all the files & folders too, simply browse to:

Why does this exist?
I had a Windows machine which was on a "secure" network, and on that machine I needed to pull a lot of files over to a Linux workstation, I had no rights to create a network share on the Windows machine, and I didn't want to copy everything off onto USB or over the network; because I'd have been creating ghostly copies of all the files on those remote and movable storage intermediaries.

So for security and integrity I wanted to get the files as straight from A to B as possible.

The Windows machine had Python installed, so opening a command prompt, I found the python exe in "/users/myself/AppData/Local/Programs/Python", so set the Path as above, then  moved to the root of the system and started the server.

On the Linux machine I had a simple Python script which called the server "index.html", which was just the file & folder list and then this python script crawled the downloaded index and called "wget" on each file, or "mkdir" for every folder... And I re-cursed down the tree...

My next post will be that very script... Because I am nice like that!

Security Lesson
To any system administrators out there... This is a loop hole on ALL machines running python, take a look if you need to stop this happening!

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