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About Devfs

Devfs is a virtual filesystem [1] meant to replace the static and ugly /dev pseudo-files. It appeared that having a lot of entries in /dev, "just in case" was not the good approach, neither were the (complicated) scripts to create the entries when needed.

It features a new, cleaner naming pattern (ex.: /dev/hda1 is now /dev/ide/host0/bus0/lun0/part1 ). For obvious compatibility reasons, a daemon, devfsd is available, which can create links with the old filename for devices on-the-fly.

It is dynamic: it will create /dev entries when the modules are loaded and then when the hardware is present. This presents the double [2] benefit of being more readable to human beings, and matching the real hardware on the machine(really useful for USB/IEEE1394/whatever).

It is virtual, and that's what makes it really interesting in read-only root filesystems like Plume uses. It doesn't need write access to the root filesystem, like Plume's alternatives do [3].

Note: Devfs has been obsoleted by Sysfs and Udev in the 2.6 kernel. Most remarks in this article apply to Sysfs also, though.


[1] like procfs for /proc

[2] it also saves disk space and time seeking through the device files, but not really much

[3] ugly, ugly things like linking /dev to a ramdisk and copying or creating device files on each boot