software/pynsfs

Python Namespace File System

Author: Bryan Newbold
Date: July 2008
URL: http://git.bnewbold.net?p=pynsfs.git;a=summary

This is an experimental implementation of a python namespace as a virtual file system, implemented using the python bindings for fusefs on unix.

At this point only the global namespace of the filesystem instance itself is accessible, and only limited access is available to that. If anything goes wrong it can cause a hard lock and system crash; don't leave it running and don't try to write anything substantial.

The source code can be checked out from the above URL.

Features

An example session goes like:

snark# ls /mnt/python/

snark# python nsfs.py /mnt/python/
*** init complete
let's go!

snark# cd /mnt/python/

snark# ls -l
total 6
-r--r--r--  1 root  wheel  30 Dec 31  1969 DefaultStat
-r--r--r--  1 root  wheel  33 Dec 31  1969 DefaultStatVfs
-r--r--r--  1 root  wheel  19 Dec 31  1969 Fuse
-r--r--r--  1 root  wheel  30 Dec 31  1969 NamespaceFS
-r--r--r--  1 root  wheel  27 Dec 31  1969 NsfsFile
-r--r--r--  1 root  wheel  17 Dec 31  1969 StringIO
drwxr-xr-x  2 root  wheel   0 Dec 31  1969 __builtins__
-r--r--r--  1 root  wheel   4 Dec 31  1969 __doc__
-r--r--r--  1 root  wheel   7 Dec 31  1969 __file__
-r--r--r--  1 root  wheel   8 Dec 31  1969 __name__
drwxr-xr-x  2 root  wheel   0 Dec 31  1969 _find_fuse_parts
drwxr-xr-x  2 root  wheel   0 Dec 31  1969 errno
drwxr-xr-x  2 root  wheel   0 Dec 31  1969 fuse
-r--r--r--  1 root  wheel  29 Dec 31  1969 main
drwxr-xr-x  2 root  wheel   0 Dec 31  1969 os
drwxr-xr-x  2 root  wheel   0 Dec 31  1969 stat
-r--r--r--  1 root  wheel  24 Dec 31  1969 time

snark# ls stat/
ST_ATIME        S_ENFMT         S_IMODE         S_ISDIR         S_IWRITE
ST_CTIME        S_IEXEC         S_IREAD         S_ISFIFO        S_IWUSR
ST_DEV          S_IFBLK         S_IRGRP         S_ISGID         S_IXGRP
ST_GID          S_IFCHR         S_IROTH         S_ISLNK         S_IXOTH
ST_INO          S_IFDIR         S_IRUSR         S_ISREG         S_IXUSR
ST_MODE         S_IFIFO         S_IRWXG         S_ISSOCK        __builtins__
ST_MTIME        S_IFLNK         S_IRWXO         S_ISUID         __doc__
ST_NLINK        S_IFMT          S_IRWXU         S_ISVTX         __file__
ST_SIZE         S_IFREG         S_ISBLK         S_IWGRP         __name__
ST_UID          S_IFSOCK        S_ISCHR         S_IWOTH

snark# cat time 
<built-in function time>

snark# echo " Hello Python" >> os/__name__

snark# cat os/__name__
os Hello Python

snark# rm time

snark# ls
DefaultStat             __builtins__            fuse
DefaultStatVfs          __doc__                 main
Fuse                    __file__                os
NamespaceFS             __name__                stat
NsfsFile                _find_fuse_parts
StringIO                errno

snark# ln __nameofos__ os/__name__ 
ln: __nameofos__: No such file or directory

snark# ln os/__name__ __nameofos__

snark# cat __nameofos__ 
os Hello Python

snark# cd ..

snark# umount /mnt/python/

The root directory is the global namespace; modules are available as subdirectories and all other objects are accessible as files. Strings can be appended to; all other "files" are readonly and return their string representation. "Files" can be deleted; "directories" can not. Hard links to files are possible.

Requirements

This was developed and has only been tested on FreeBSD 7.0 with Python 2.5.1 version 0.2 of the python-fuse bindings.

FUSE Filesystem installed and configured on a compatible operating system
Recent version of Python
FUSE Python Bindings

Once everything is installed and configured, the script can just be run as root; no installation necessary.

Usage

Try # python nsfs.py -h to get a list of general FUSE options. A simple mount command would look like:

# python nsfs.py /mnt/python

To unmount:

# umount /mnt/python

I like to run in foreground, single threaded, with debug info:

# python nsfs.py -dsf /mnt/python

Really only basic command line tools work because they don't check for many attributes; try echo "blah" >> file, cat file, df -h, ls -l etc.

TODO

Functions taking simple arguments (or no arguments) could be implemented as character devices; function_name.doc, function_name.repr, etc could give meta-information.

File of the form __thing__ should be renamed .thing.

New files should be allowed and saved as strings.

CHANGELOG

July 28, 2008: First implementation