udev vs. /dev

[/root]

I am new to Linux (one week) and have been reading what's new in the Linux
- primarily udev.

Can someone please clarify and distinct the main difference between udev
and /dev and its significance - in easy to understand terms...please?

Thank you kindly.

[ric_man]

It sounds like you're a little confused as to what udev, devfs, and /dev
is (unless I'm reading your post incorrectly). Hopefully the 3rd point
of this article will clarify somethings for you:

http://www.gentoo.org/doc/en/migration-to-2.6.xml

...Ric
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[hyperfusion]

/dev is a directory (aka a folder) on your system. the files in /dev
represents the devices on your system (/dev/hda would be the first ATA
drive on your system, /dev/sdb would be the second SCSI drive, etc.)

udev, on the other hand, is a program (daemon) that manages the files
in /dev. devfs and udev pretty much do the same thing, but each has its
advantages and disadvantages. you can google for udev/devfs to find
more info.

i hope this helps

[James McIninch]

/dev is a directory, udev is a service that puts entries in the directory.

More specifically, /dev is the directory Linux and UNIX systems use to store
"device special files", which are accessible like files, but are really
interfaces to device drivers. For example, /dev/ttyS0 is a file that's
really a front-end to the serial driver. The original way that device
entries appeared under /dev was if you used the utility mknod to create
them, specifying a pair of integers which where registered with a
particular device driver that handled that sort of device, and a qualifier
'c' or 'b' that specified whether the device was manipulated using the
rules associated with streams of characters (c) or blocks of data (b).

'udev' is a system (a daemon and filesystem) that automagically populates
the contents of /dev with device files that reflect the hardware actually
installed on your machine. With udev, if you plug in a device (like a USB
drive) the entry appears under /dev for the device. udev actually relies on
the the 2.6 sysfs feature that contains information about the system. udev
has some shortcomings in that not all devices are correctly indicated by
sysfs (firewire video being a big one), so it's not for everyone. A good
comporomise is devfs (udev's predecessor) which combines on-disk device
entries with some auto-configuration features.

/root wrote:

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