Hello, Neil. On Tue, Mar 13, 2012 at 09:33:30PM +0000, Neil Bothwick wrote: > On Tue, 13 Mar 2012 21:07:37 +0000, Alan Mackenzie wrote:
> > But I really meant what functionality udev has that mdev lacks. For > > example, mdev this morning recognised my USB stick being inserted, and > > created /dev/sdc for it. > udev does a *lot* more than that, for example the persistent naming of > network interfaces. More significantly, it can run programs based on > device rules. This is where I start getting unhappy. Is there any need for this blurring? Having device nodes is essential to a linux system, and some programs use these nodes. Why must they be mashed together into a tasteless mush? Is there some advantage to this I haven't twigged yet? > For example, usb_modeswitch installs a udev rule to switch a 3G USB > modem from CD to modem mode, without which it won't work. Same question as above: why does that switching have to be done via the device node system rather than via the driver. Isn't that what drivers are for? > That's fine when you plug it into a running system, but when you boot > with it plugged in, it can trip over itself because the usb_modeswitch > executable is in /usr/sbin. Er, that's a different discussion altogether. ;-) > You could use this to argue that /usr should be mounted before udev is > started, but you could just as well use it to argue that udev should not > be trying to run such rules at the boot runlevel. Or that udev shouldn't have "rules". I still don't understand the basic concept driving this thing. My HDDs don't need rules - they just need a mapping from /dev/sd[ab] into device 8/0 and 8/16, and the appropriate drivers built into my kernel. Am I being stupid? Despite your example above, I still don't see what udev is about, why it's necessary, or even why it's advantageous. > -- > Neil Bothwick -- Alan Mackenzie (Nuremberg, Germany).
