Filesystem in Userspace ( FUSE ) Tutorial

FUSE is an mechanism which allows to create own file systems to non-privileged users without editing the kernel code. Initially it was developed to support for AVFS ( A Virtual File System ). After that it will be taken as separate project. It runs file system code in user space while the FUSE module provides only a "bridge" to the actual kernel interfaces. Check the FUSE structure, it will help you to understand about FUSE.

Installation :

To use FUSE , you must be install this on your system. Just follow my steps.

Step 1 : Download FUSE 2.9.3 ( latest version ) from the following link.

==> FUSE 2.9.3.tar.gz

Step 2 : After downloaded FUSE, open terminal and move to Downloads directory by

cd Downloads

Step 3 : Extract FUSE 2.9.3.tar.gz file by

tar -zxvf fuse-2.9.3.tar.gz

Step 4 : Move to fuse-2.9.3 directory by

cd fuse-2.9.3

Step 5 : Install FUSE by

sudo ./configure

sudo make

sudo make install

Working :



Step 6 : Just create a new directory to work with on FUSE by

mkdir fusep

move to fusep directory as

cd fusep

Step 7 : Create simple helloworld program using  C program by

gedit hello.c

Now copy the following program and paste into hello.c file

#define FUSE_USE_VERSION 26

#include <fuse.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>

static const char *hello_str = "Hello World!\n";
static const char *hello_path = "/hello";

static int hello_getattr(const char *path, struct stat *stbuf)
{
 int res = 0;

 memset(stbuf, 0, sizeof(struct stat));
 if (strcmp(path, "/") == 0) {
  stbuf->st_mode = S_IFDIR | 0755;
  stbuf->st_nlink = 2;
 } else if (strcmp(path, hello_path) == 0) {
  stbuf->st_mode = S_IFREG | 0444;
  stbuf->st_nlink = 1;
  stbuf->st_size = strlen(hello_str);
 } else
  res = -ENOENT;

 return res;
}

static int hello_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
    off_t offset, struct fuse_file_info *fi)
{
 (void) offset;
 (void) fi;

 if (strcmp(path, "/") != 0)
  return -ENOENT;

 filler(buf, ".", NULL, 0);
 filler(buf, "..", NULL, 0);
 filler(buf, hello_path + 1, NULL, 0);

 return 0;
}

static int hello_open(const char *path, struct fuse_file_info *fi)
{
 if (strcmp(path, hello_path) != 0)
  return -ENOENT;

 if ((fi->flags & 3) != O_RDONLY)
  return -EACCES;

 return 0;
}

static int hello_read(const char *path, char *buf, size_t size, off_t offset,
        struct fuse_file_info *fi)
{
 size_t len;
 (void) fi;
 if(strcmp(path, hello_path) != 0)
  return -ENOENT;

 len = strlen(hello_str);
 if (offset < len) {
  if (offset + size > len)
   size = len - offset;
  memcpy(buf, hello_str + offset, size);
 } else
  size = 0;

 return size;
}

static struct fuse_operations hello_oper = {
 .getattr = hello_getattr,
 .readdir = hello_readdir,
 .open  = hello_open,
 .read  = hello_read,
};

int main(int argc, char *argv[])
{
 return fuse_main(argc, argv, &hello_oper, NULL);
}

Save the file and close it.

Step 8 : Compile the above program by

gcc -Wall hello.c `pkg-config fuse --cflags --libs` -o hello

Step 9 : After compilation create tmp directory and run object file. Just enter the commands one-by-one given below

mkdir tmp

./hello tmp/

ls tmp/

cat tmp/hello

Thats all. You are done.

To unmount tmp directory enter the following command...

umount tmp

If you have any queries, post it in comments. We will help you.