Add a new section in multipath.conf.5 to clarify wwid generation
and update wrong defaults for the property whitelist.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
multipath.conf.defaults | 2 +-
multipath/multipath.conf.5 | 33 ++++++++++++++++++++++++++++-----
2 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/multipath.conf.defaults b/multipath.conf.defaults
index a12a4f4..a4e8f75 100644
--- a/multipath.conf.defaults
+++ b/multipath.conf.defaults
@@ -73,7 +73,7 @@
# }
#}
#blacklist_exceptions {
-# property "(ID_SCSI_VPD|ID_WWN)"
+# property "(SCSI_IDENT_.*|ID_WWN)"
#}
#devices {
# device {
diff --git a/multipath/multipath.conf.5 b/multipath/multipath.conf.5
index 7e17f62..6980010 100644
--- a/multipath/multipath.conf.5
+++ b/multipath/multipath.conf.5
@@ -55,9 +55,8 @@ section.
.TP
.B multipaths
This section defines the multipath topologies. They are indexed by a
-\fIWorld Wide Identifier\fR(wwid), which is taken to be the value of
-the udev attribute given by the
-\fIuid_attribute\fR keyword.
+\fIWorld Wide Identifier\fR(wwid). For details on the wwid generation
+see section \fBWWID generation\fR below.
.TP
.B devices
This section defines the device-specific settings.
@@ -176,7 +175,7 @@ identifier. Default value is
.B getuid_callout
The default program and args to callout to obtain a unique path
identifier. Should be specified with an absolute path.
-This parameter is deprecated; \fIuid_attribute\fR should be used instead.
+This parameter is deprecated.
.TP
.B prio
The name of the path priority routine. The specified routine
@@ -534,7 +533,7 @@ The \fIWorld Wide Identification\fR of a device.
.TP
.B property
Regular expression of the udev property to be whitelisted. Defaults to
-.I (ID_WWN|ID_SCSI_VPD)
+.I (ID_WWN|SCSI_IDENT_.*)
.TP
.B devnode
Regular expression of the device nodes to be whitelisted.
@@ -771,6 +770,30 @@ sections:
.RE
.PD
.LP
+.SH "WWID generation"
+Multipath uses a \fIWorld Wide Identification\fR (wwid) to determine
+which paths belong to the same device. Each path presenting the same
+wwid is assumed to point to the same device.
+.LP
+The wwid is generated by three methods (in the order of preference):
+.TP 17
+.B getuid_callout
+Use the specified external program; cf \fIgetuid_callout\fR above.
+Care should be taken when using this method; the external program
+needs to be loaded from disk for execution, which might lead to
+deadlock situations in an all-paths-down scenario.
+.TP
+.B uid_attribute
+Use the value of the specified udev attribute; cf \fIuid_attribute\fR
+above. This method is preferred to \fIgetuid_callout\fR as multipath
+does not need to call any external programs here. However, under
+certain circumstances udev might not be able to generate the requested
+variable.
+.TP
+.B vpd_pg83
+If none of the \fIgetuid_callout\fR or \fIuid_attribute\fR parameters
+are present multipath will try to use the sysfs attribute
+\fIvpd_pg83\fR to generate the wwid.
.SH "KNOWN ISSUES"
The usage of
.B queue_if_no_path
--
1.8.4.5
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