lsluns: clarify discovery use case, relation to NPIV and to zfcp auto LUN scan

Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Reviewed-by: Jens Remus <jremus@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>

zconf/lsluns

@@ -174,6 +174,9 @@ $PROGRAM_NAME [-c <busid>] ... [-p <wwpn>] ... [-h] [-v]
 
     List LUNs discovered in the Fibre Channel (FC) Storage Area Network (SAN).
     This causes extra SAN traffic for each target port WWPN.
+      Discovering LUNs only makes sense for NPIV-enabled FCP devices
+    without zfcp automatic LUN scan. zfcp automatic LUN scan is available
+    as of kernel version 2.6.37, if not disabled with zfcp.allow_lun_scan=0.
 
 $PROGRAM_NAME -a [-c <busid>] ... [-p <wwpn>] ... [-h] [-v]
 

zconf/lsluns.8

@@ -46,6 +46,24 @@ encryption, use other tools such as
 or
 .BR "lsscsi \-tv" .
 
+.SS Details on lsluns without -a option
+
+.TP
+Prerequisite
+Discovering LUNs only makes sense for NPIV-enabled FCP devices
+without zfcp automatic LUN scan. zfcp automatic LUN scan is available
+as of kernel version 2.6.37, if not disabled with zfcp.allow_lun_scan=0.
+
+With available and enabled zfcp automatic LUN scan,
+the kernel already performs LUN discovery.
+
+.TP
+Temporary LUN Attachment
+If not attached already, lsluns temporarily attaches LUN 0
+(or if this fails the WLUN 0xc101000000000000) during runtime.
+Do not terminate lsluns with a signal. Signals interfere
+with the removal of temporarily attached LUNs.
+
 .SH OPTIONS
 .TP
 .BR \-a ", " \-\-active