HOTPLUG(8)						     Linux Programmer's Manual							HOTPLUG(8)

NAME

       hotplug - Linux hotplugging support scripts

SYNOPSIS

       hotplug [ help | --help | NAME ]

DESCRIPTION

       hotplug	is a program which is used by the kernel to notify user mode software when some significant (usually hardware-related) events take
       place.  An example is when a USB or Cardbus device has just been plugged in.  This is useful for automatically loading and setting up driv-
       ers, packaged either as kernel modules or as user mode programs.

       The  hotplug  program path name is registered in /proc/sys/kernel/hotplug, and normally holds the value /sbin/hotplug.  Except for special-
       ized configurations such as initrd(4) configurations, that identifies a shell script which delegates to specific "policy agents", /etc/hot-
       plug/NAME.agent.   The  name  of  the agent is given by the kernel as the first command-line parameter.	The name corresponds to a specific
       kernel subsystem whose events it processes (e.g. "usb", "pci", "net" etc.).

       Information about an event is usually passed to agents in the form of environment variables.  Most agents accept a "ACTION"  variable  that
       describes  the type of the event.  It can be, for example, "add" or "remove" to signify that some device has just been connected to or dis-
       connected from the system respectively.	In such requests, agents are also given variables describing at the device (and its  location)	so
       that they can choose the appropriate drivers to set up.

       hotplug	agents	aren't	necessarily called only by the kernel though.  While the OS is initializing, the "cold-plugging" case, the hotplug
       script in /etc/init.d/hotplug is invoked to make sure that all device connected at boot are properly configured, applying the same rules as
       if they were connected later.

FILES

       /proc/sys/kernel/hotplug   specifies hotplug program path
       /sbin/hotplug		  hotplug program (default path name)
       /etc/hotplug/*		  hotplug files
       /etc/hotplug/NAME.agent	  hotplug subsystem-specific agents
       /etc/hotplug/NAME*	  subsystem-specific files, for agents
       /etc/hotplug/NAME/*	  driver setup scripts, invoked by agents

SEE ALSO

       initrd(4)

       The http://linux-hotplug.sourceforge.net/ web site.

AUTHORS

       hotplug is developed by Linux Hotplugging Project http://linux-hotplug.sourceforge.net/

       This manual page was originally written by Fumitoshi UKAI <ukai@debian.or.jp>, for the Debian GNU/Linux system (but may be used by others),
       based on original Japanese version of manpage.

								   February 2001							HOTPLUG(8)