On Mon, Nov 22, 2004 at 02:50:44PM -0500, Christian Convey wrote: > Can anyone help clarify the relationship between any of the following > things that may or may not be on my computer? > hotplug When an event happens on any of the various buses (pci, usb, firewire, etc.) such as device connection, removal, etc., the kernel that supports hotplug will call /sbin/hotplug, which is a user-space program that will do something based on the events. The standard hotplug program that most people use is at linux-hotplug.sourceforge.net, but you could always write your own. > udev Udev plugs in to the standard hotplug program and responds to hotplug events by creating or destroying device nodes in /dev, based on policies that you define. > devfs Devfs is a kernel module that implements a filesystem. Modules register with devfs to tell it what devices nodes they need, and devfs creates and destroys the device nodes as the modules are loaded/unloaded. Devfsd adds extra policy information, such as device permissions and adding symlinks to devices. > automount > autofs Automounters watch for access to a directory, and automatically mount a filesystem on that directory when a process tries to access it. They are used mostly for automatically mounting NFS filesystems, but can be used to mount anything. I'm not sure what automount program you are referring to, but historically, automount (and amd) were user-level automounters, while autofs is a kernel-level automounter. user-level automounters manage a special hidden directory of mountpoints and create symlinks into that directory when a mount happens. Autofs can mount things in-place without the need for symlinks, which is generally better. > HAL Hardware abstraction layer. Would need more context as to whose HAL you're talking about. > sysfs > procfs Both of these are methods for kernel subsystems to export information to userspace, and for userspace to change operation of the kernel subsystems. Procfs has been around for quite a while, and I believe it was originally used just to export information about processes. Other modules started adding their own files into /proc, and the format of these items was all very ad hoc. Sysfs is an attempt to formalize this into a consistent hierarchy, and to separate process information from device information into two different filesystems. Note that udev needs sysfs in order to work properly. > - Does hotplug inform udev when a new device connects to the computer? Yes, assuming that you're using the Debian hotplug package. > - Does udev make use of devfs? No, udev is designed as a replacement for devfs that doesn't have any kernel-level coupling. -- Dave Carrigan Seattle, WA, USA dave@rudedog.org | http://www.rudedog.org/ | ICQ:161669680 UNIX-Apache-Perl-Linux-Firewalls-LDAP-C-C++-DNS-PalmOS-PostgreSQL-MySQL Dave is currently listening to The Replacements - Takin' A Ride (Live, 1982-10-01)
Attachment:
signature.asc
Description: Digital signature