File System (3 people)

implement a file system interface using binary files

• The file system reserves the first part of the disk to store:

  • a Header sections for storing disk info
  • a linked list of free blocks
  • a single global directory

• Blocks are of two types

  • data blocks
  • directory blocks

  A data block are "random" information A directory block contains a sequence of structs of type "directory_entry", containing the blocks where the files in that folder start and if they are directory themselves

• Create functions to use the filesystem, in detail:

  • Create a file (touch)
  • Create a directory (mkdir)
  • Print the contents of the directory (ls)
  • Print the contents of the file (cat)
  • Write into file (echo-like)
  • Delete a directory/file (rm)

Disk Structure

The disk contains in the first location its Header, then the bitmap. After the bitmap it can contain files, or directories.

FS Structure

The user can load an existing disk or a create a new one, specifying the number of blocks contained in the disk. When the disk is created the FS creates also the root directory.

Upon loading a disk or creating a new one the user can start creating directories or file just like any normal filesystem.

Every file is indexed, the fcb of the file is the beginning of a linked list of Indexes which store the position in disk of the corresponding data block. A file is formed by two linked lists, one for the indexes and one for the data blocks.

A directory is a file, but with only a linked list of directory blocks, which store the position on disk of the files contained in the directory.

Shell

To use our filesystem we have included a shell, which performs all the filesystem functions. all the commands in the shell begin with a / (eg. /ls to perform ls command). to have a list of the commands in the shell type /help.

For further details see our report.