FFS

FFS is a custom, persistent, virtual file system built with FUSE. Virtual file systems run on top of an already existing, more robust, and more reliable file system. The virtual file system is responsbile for maintaining the file system tree structure. Most virtual file systems built with FUSE usually do not implement any level of persistence, however, FFS does. FFS uses a file, at ~/Desktop/file.txt by default, to store data across mounts and machine reboots. FFS also requires a mountpoint through which normal FS operations can be done. By default, it is ~/Desktop/mountpoint.

Ideally, once mounted, normal Linux operations such as create, open, read, write, and so on, can be done for files stored inside the mountpoint as if it were any other directory.

Running FFS

Clone the repo

git clone https://github.com/avinashshenoy97/ffs ffs

cd into the repo

cd ffs

Edit the Makefile and replace the username with your username

username = <your username here>

Compile and run our version of mkfs to initialise the file system by running

make mkfs

Start FFS with default mountpoint by typing make inside the ffs folder.

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To use a different mountpoint and persistent disk file, first compile and run our MKFS

gcc -Wall ffs_operations.c tree.c disk.c bitmap.c mkfs.c -D_FILE_OFFSET_BITS=64 -o mkfs `pkg-config fuse --libs` -DFUSE_USE_VERSION=22 -lm

./mkfs <path_to_persistent_storage>

Then compile and run FFS

gcc -Wall ffs_main.c ffs_operations.c tree.c disk.c bitmap.c -D_FILE_OFFSET_BITS=64 -o ffs `pkg-config fuse --libs` -DFUSE_USE_VERSION=22 -lm

./ffs -f <path to mount point>

To run as background daemon,

./ffs <path to mount point>

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Flags to ./ffs

There are several flags that can be passed to the ./ffs to tweak how FUSE will run FFS.

FLAG	MEANING	CONSEQUENCE
-d	Debug mode	Additional debugging information is printed by FUSE
-f	Run in foreground	Without this flag, FFS will be run as a background daemon
-s	Single threaded	FFS runs in single threaded mode. Without this flag, FFS would run on multiple threads, possibly making it faster.

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Flags to gcc

Several flags are passed to gcc while compiling FFS. Here is a table to understand their meaning.

FLAG	MEANING	CONSEQUENCE
-Wall	Turn on warnings	Display all warnings
-g	Add debugging symbols	The program is compiled with debugging symbols and other information that can be used by tools like gdb for debugging.
-o	Output executable	Used to set the name of the compiled executable.
-D_FILE_OFFSET_BITS=64	Required by FUSE	This is a flag required by this version of FUSE.
`pkg-config fuse --libs` -DFUSE_USE_VERSION=22	Required	These flags are required to use the correct version of FUSE, the same version used to develop FFS.
-lm	Link math library	Used to link the math library for functions like pow
-DERR_FLAG	Error logging file	A flag used by FFS to enable/disable helpful debugging info while FFS runs. (FFS must run in the foreground to view these messages).

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The mountpoint, by default, is a folder created on the Desktop. You can cd into ~/Desktop/mountpoint and test the file system by running common commands like

mkdir a
cd a
mkdir b
cd b
pwd
echo "Abc" > c.txt
cd ..
ls
ls -a
cd ..
tree

The output should look like

Use this command to unmount FFS (remember to cd out of it first!)

fusermount -u ~/Desktop/mountpoint

Debug Mode

FFS can be compiled and run in debug mode by

make drun

To just compile in debug mode

make dcompile

Again, the default mountpoint and file path are used. To specify the path to mountpoint and file manually,

gcc -Wall -g -DERR_FLAG ffs_main.c ffs_operations.c tree.c disk.c bitmap.c -D_FILE_OFFSET_BITS=64 -o ffs `pkg-config fuse --libs` -DFUSE_USE_VERSION=22 -lm

./ffs -d -f -s <path to mount point>

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Pimary Contributors

	Anvith Shetty
	Anwika Bhandary
	Avinash Shenoy