+
+.SH USAGE WITH UDEV
+
+If \fBscsi_id\fP is invoked with one argument without a leading \-, it
+assumes it is called for a hotplug event, and looks for the sysfs device
+in the DEVPATH environment variable. This mode is deprecated, but
+available for backwards compatibility.
+
+If the DEVPATH environment variable is set, scsi_id assumes it has been
+invoked via udev (or some other hotplug program), and all errors or
+warnings are sent using syslog.
+
+To determine the specific value needed in a RESULT key, use the \-s option,
+for example:
+
+.sp
+.nf
+/sbin/scsi_id -s /block/sda
+.fi
+.P
+
+\fBscsi_id\fP is one of the tools used in the "Linux Persistent Device Names"
+scheme that creates persistent device links in /dev/disk. It is called with
+the -x option which will print all values in a defined format to let udev
+import it into its own environment for later event processing.
+.sp
+An example custom \fBudev\fP rule using \fBscsi_id\fP, that will name a block
+device and any partitions for the device matching the \fBscsi_id\fP output
+of 312345:
+
+.sp
+.nf
+BUS=="scsi", PROGRAM=="/sbin/scsi_id -d %N -s %p", RESULT=="312345", NAME="disk%n"
+.fi
+.P
+