Udev...

[phunni]

Not sure if this should be in hardware, but I figured since Udev relates to devices it probably should. Mods, feel free to move it if you disagree...

 

Anyway, when I last installed Linux I isntalled Udev instead of devfs because it seemed to me to be more cutting edge. Trouble is, I don;t really ahve a clue what it is or, more importantly, how to configure it. I reckon this could well be really useful to properly get to grips with it. Can anyone either explain it or point me to a useful tutorial please?

 

[arthur]

http://www.kernel.org/pub/linux/utils/kern...otplug/udev-FAQ

 

http://www.gentoo.org/doc/en/udev-guide.xml

 

if you type "ls /dev" on a devfs (old) machine, you'll get hundreds of files, even for devices you don't have. This is because in the old system device nodes couldn't be dynamically added.

 

on a udev system, the /dev/ folder is empty, but populated upon bootup. when you add a device, a node/file is created in /dev/, and removed when you remove the device. That's about as far as my knowledge on it goes, but I run a pure udev system and found that it works flawlessly. If I plug in my DVD writer, /dev/dvd appears in the folder, and I simply mount it.

[paul]

I use some udev rules to rename devices

On my laptop I have lan0, and wifi0

on my firewall I have lan0, iconz0. wave0, wave0:1, and golive0 (lan + 3 ISPs)

[AussieJohn]

Courtesy of wikipedia.

 

Cheers. John.

 

 

 

 

 

Udev

From Wikipedia, the free encyclopedia.

 

The title given to this article is incorrect due to technical limitations. The correct title is udev. udev is a file system replacement for DevFS on the Linux 2.6 kernel series. Its primary function is managing device nodes in /dev.

Contents [showhide]

1 New features in udev

2 Operation

3 Authors

4 External links

[edit]

 

New features in udev

 

Unlike the traditional system of managing devices in Linux, which used a static set of device nodes, udev dynamically provides nodes for only the devices actually present on a system. Although devfs also provided such functionality, advocates for udev cited a number of reasons for preferring its implementation over devfs:[1] (http://kernel.org/pub/linux/utils/kernel/hotplug/udev_vs_devfs)

 

* udev is independent of major and minor device numbers, whereas devfs did not address the need for dynamic device numbers

* Unlike devfs, udev supports giving devices persistent names, which do not depend on, for example, the order in which the devices are plugged into the system.

* udev executes executes in user space, as opposed to devfs' kernel space. One consequence is that udev moves naming policy out of the kernel.

* udev is smaller and unlike devfs, complies with the Linux Standard Base naming system.

* According to some developers, devfs suffered from lack of maintenance and contained unfixable design flaws and race conditions.

 

[edit]

 

Operation

 

udev allows for rules that specify what device name is given to a specific device, regardless of which port it is plugged into. For example, a rule to always mount a hard drive with manufacturer "iRiver" and device code "ABC" as /dev/iriver is possible. This consistent naming of devices guarantees that scripts dependent on a specific device's existence will not be broken.

 

udev works by receiving /sbin/hotplug calls sent by the kernel whenever a device is added or removed from the system.

[edit]

 

Authors

 

udev was developed by Greg Kroah-Hartman in collaboration with Dan Stekloff, Kay Sievers, and many others.

[edit]

 

External links

 

* Discussion of udev rules (http://www.reactivated.net/writing_udev_rules.html)

* udev FAQ (http://www.kernel.org/pub/linux/utils/kern...otplug/udev-FAQ)

* The Gentoo udev Guide (http://www.gentoo.org/doc/en/udev-guide.xml)

 

Retrieved from "http://en.wikipedia.org/wiki/Udev"

 

Categories: Computer file systems | Linux

[iphitus]

You shouldnt need to compile udev from source or configure it from scratch, your distro should provide packages with a basic working config.

 

Arthur: you only get the massive /dev with heaps of files with a static /dev/ filesystem. with devfs you dont get the huge amount of files.

 

Udev is really cool in what it can do, i have it making its /dev entries for my external hard drive as /dev/lacieX, my flash drive, /dev/usbstick, my sd card reader /dev/sdcard

 

iphitus

[adamw]

Yeah. If you install MDV 10.1 or 2005 you have udev already, it's sitting there doing its work, don't sweat it :). So long as all your devices work, you never need to worry about it, just let it work.

[SoulSe]

I've been running udev for a long time already, but I've never really used it to its full potential or even found out more about it... I think I was too excited by HAL and gnome-volume-manager at the time :P

[phunni]

You shouldnt need to compile udev from source or configure it from scratch, your distro should provide packages with a basic working config.

 

Arthur: you only get the massive /dev with heaps of files with a static /dev/ filesystem. with devfs you dont get the huge amount of files.

 

Udev is really cool in what it can do, i have it making its /dev entries for my external hard drive as /dev/lacieX, my flash drive, /dev/usbstick, my sd card reader /dev/sdcard

 

iphitus

<{POST_SNAPBACK}>

 

Currently using Arch and it does have plenty of udev configs out of the box - but they need tweaking to get things like my clie etc... worknig with it...