MinorFs

MinorFs is a fantastic userspace (fuse) filesystem that has been designed to implement private storage for pseudo-persistent processes. The file system provided by MinorFs is based on a simple view and allows processes to become pseudo-persistent processes. This is achieved by giving these processes n-th claim persistent storage, effectively protecting the data for that user from malware that could be running under the same user id.

MinorViewFs, another product from the same brand, creates a private directory for processes. This file system offers processes the possibility to 'claim' an unused slot previously used by a process that was an instance of the same executable running under the same user id as the current process. This claiming of a slot turns the process into an incarnation of some 'persistent' process, allowing it to make use of the 'private' directory to store its state.

MinorFs allows most operations that a normal filesystem allows, but there are some differences. Links and symlinks are not supported, and chmod operations do not have any effect in relation to the security model that MinorViewFs provides. It is important to note that minorviewfs does not work well with scripts, as the data will become private to the interpreter rather than to the script. Additionally, currently, persistent storage is limited to 32 concurrent versions of the same program running with the same uid.

MinorViewFs provides an essential operation that makes it work well with MinorCapFs. This operation is the use of a special extended attribute known as 'delegatable.' This attribute, which is made available for each file and directory, returns a path to the underlying directory but through MinorCapFs. Unlike the MinorViewFs paths, the paths into MinorCapFs can be delegated to other processes, even to other users. The MinorCapFs paths contain a token that is in fact a very basic implementation of a so-called 'password capability.'

Lastly, this version of MinorFs does not address attenuation and revocations. However, the upcoming version of MinorFs will aim to provide additional minor filesystems for these purposes. In conclusion, MinorFs is an excellent file system for anyone looking for a simple view-based filesystem that provides processes with private storage.