This documentation provides the necessary steps to build a 2.4.x Linux kernel with devfs support on an x86 machine, and to compile and test the fusd module with user-space driver examples. The Redhat 9.0 (shrike) distribution is used for testing.

fusd HOWTO

Step 1

Download a stock Linux-2.4.21 Linux kernel [4] to /usr/src from:


Step 2

Extract the kernel sources:

 cd /usr/src
 tar xjvf linux-2.4.21.tar.bz2

Step 3

Choose the following kernel options for devfs and compile the kernel:


 make clean
 make dep
 make bzImage
 make modules
 make modules_install
 cp arch/i386/boot/bzImage /boot/vmlinuz-2.4.21
 mkinitrd /boot/initrd-2.4.21.img 2.4.21

Step 4

Update the boot-loader:

Lilo was used and an entry for the new kernel is added to /etc/lilo.conf:

        append="root=/dev/hda1 devfs=nomount"

Run /sbin/lilo to update the lilo. If using grub, just add an entry for vmlinuz and initrd in /boot/grub/menu.lst.

devfs cannot understand root=LABEL= directives in the bootloader. Hence, don't use such conventions in the bootloader or in /etc/fstab. By default, we don't want devfs to mount on boot-up, hence passing devfs=nomount will not mount it during boot.

Step 5

Install devfsd.

devfsd is a daemon that needs to be installed. We used the devfsd-2.4.3-12.i386.rpm file.

 rpm -ivh devfsd-2.4.3-12.i386.rpm

Step 6

Remove any /dev/pts entry in /etc/fstab.

devfs will handle /dev/pts so any existing entry in /etc/fstab needs to be removed.

Step 7


Reboot into the new Linux-fusd kernel. If everything looks good, the system will boot. If you missed out on any of the above options, your system will be mounted as a read-only filesystem and might drop you to a console shell or may reboot.

Step 8

Compile fusd-1.10:

Download fusd-1.10 package to say /root, from:


su to root and extract the sources:

 cd /root
 tar xzvf fusd-1.10.tar.gz

Change the kernel source path in the Makefile. Compile the fusd package which will build kfusd.o, libfusd.a and code examples:

 cd fusd-1.10

If compilation is done cleanly, install it:

 make install

Step 9

Mount devfs and start devfsd:

 mount -n -t devfs none /dev
 devfsd /dev

Step 10

Load the kfusd.o module

The kfusd.o module is present in the objs.i686-linux/ directory in the fusd sources. Load the module:

 insmod objs.i686-linux/kfusd.o

Step 11

Test the helloworld example:

 objs.i686-linux/helloworld &
 cat /dev/hello-world


  1. [Doug]. Doug Glibert. 2001. Devfs and SCSI. http://sg.torque.net/sg/devfs_scsi.html.

  2. [Jeremy]. Jeremy Elson. 2003. FUSD - a Linux Framework for User-Space Devices. http://www.circlemud.org/~jelson/software/fusd/.

  3. [Richard]. Richard Gooch. 2002. Linux Devfs (Device File System) FAQ. http://www.atnf.csiro.au/people/ rgooch/linux/docs/devfs.html.

  4. [LinuxKernel]. http://www.kernel.org/pub/linux/kernel/v2.4/