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50 lines
2.0 KiB
D
50 lines
2.0 KiB
D
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/etc/dev.d/ How it works, and what it is for
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by Greg Kroah-Hartman <greg@kroah.com> March 2004
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The /etc/dev.d directory works much like the /etc/hotplug.d/ directory
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in that it is a place to put symlinks or programs that get called when
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an event happens in the system. Programs will get called whenever the
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device naming program in the system has either named a new device and
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created a /dev node for it, or when a /dev node has been removed from
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the system due to a device being removed.
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The directory tree under /etc/dev.d/ dictate which program is run first,
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and when some programs will be run or not. The device naming program
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calls the programs in the following order:
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/etc/dev.d/DEVNODE/*.dev
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/etc/dev.d/SUBSYSTEM/*.dev
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/etc/dev.d/default/*.dev
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The .dev extension is needed to allow automatic package managers to
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deposit backup files in these directories safely.
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The DEVNODE name is the name of the /dev file that has been created.
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This value, including the /dev path, will also be exported to userspace
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in the DEVNODE environment variable.
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The SUBSYSTEM name is the name of the sysfs subsystem that originally
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generated the hotplug event that caused the device naming program to
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create or remove the /dev node originally. This value is passed to
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userspace as the first argument to the program.
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The default directory will always be run, to enable programs to catch
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every device add and remove in a single place.
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All environment variables that were originally passed by the hotplug
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call that caused this device action will also be passed to the program
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called in the /etc/dev.d/ directories. Examples of these variables are
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ACTION, DEVPATH, and others. See the hotplug documentation for full
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description of this
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An equivalent shell script that would do this same kind of action would
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be:
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DIR="/etc/dev.d"
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export DEVNODE="whatever_dev_name_udev_just_gave"
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for I in "${DIR}/$DEVNODE/"*.dev "${DIR}/$1/"*.dev "${DIR}/default/"*.dev ; do
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if [ -f $I ]; then $I $1 ; fi
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done
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exit 1;
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