[erlang-questions] simple virtual file system in Erlang?

Jesper Louis Andersen jesper.louis.andersen@REDACTED
Sun Mar 26 16:57:43 CEST 2017

The simplest way is probably to map a path to its data, where the path is a
list of components. That is, the UNIX file ls in /usr/bin would be
represented as ["usr", "bin", "ls"].

But you could also go the way of Plan9's venti. Map something like ["usr",
"bin", "ls"] into a sha3 checksum of the data currently residing in the
file and keep the data inside a storage suitable for storing data by its
content addressing. venti also extends this by storing a tree of 64
kilobyte blocks which can then be regarded as the data when taken together.
Thus, you have two components: the data store, and the path mapping
service, mapping a path to the underlying data.

This idea has the advantage of being practically useful in many situations
beside a toy example :)

On Sun, Mar 26, 2017 at 2:46 PM Marco Molteni <marco.molteni@REDACTED>

> Hello colleagues,
> I would like to start from the presentation "Build an FTP Server with
> Ranch in 30 Minutes" and really build an FTP server, so at a certain point
> I need to hit the filesystem.
> Since the idea is still as a presentation (as opposed to building a
> production FTP server) I don't want to touch the real filesystem of the
> host, I want to use a as simple as possible virtual filesystem. It could be
> backed by DETS or Mnesia for example, or it could stay only in memory.
> On the other hand, it must still behave as a filesystem, that is, it must
> be hierarchical, so a direct mapping to a key/value store would not be
> enough. In the spirit of simplicity, I don't need any concept of read/write
> permission, I simply need a sort of graph with two types: inner nodes are
> directories, leaf nodes are files or empty directories.
> I am thinking to use DETS and somehow introduce a very simple intermediate
> layer that would offer the impression to be in a graph (each non-leaf node
> a directory) and map it to the DETS key/value API.
> Any suggestions?
> thanks
> marco
> [1] https://ninenines.eu/articles/ranch-ftp/
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