vdev_id support for device link aliases

Add a vdev_id feature to map device names based on already defined
udev device links.  To increase the odds that vdev_id will run after
the rules it depends on, increase the vdev.rules rule number from 60
to 69.  With this change, vdev_id now provides functionality analogous
to zpool_id and zpool_layout, paving the way to retire those tools.

A defined alias takes precedence over a topology-derived name, but the
two naming methods can otherwise coexist. For example, one might name
drives in a JBOD with the sas_direct topology while naming an internal
L2ARC device with an alias.

For example, the following lines in vdev_id.conf will result in the
creation of links /dev/disk/by-vdev/{d1,d2}, each pointing to the same
target as the device link specified in the third field.

  #     by-vdev
  #     name     fully qualified or base name of device link
  alias d1       /dev/disk/by-id/wwn-0x5000c5002de3b9ca
  alias d2       wwn-0x5000c5002def789e

Also perform some minor vdev_id cleanup, such as removal of the unused
-s command line option.

Signed-off-by: Brian Behlendorf <[email protected]>
Closes #981

1 files changed, 9 insertions, 4 deletions

diff --git a/man/man8/vdev_id.8 b/man/man8/vdev_id.8
index 612a50bbe..70956c634 100644
--- a/man/man8/vdev_id.8
+++ b/man/man8/vdev_id.8
@@ -19,15 +19,20 @@ drives.  Slot numbers may also be re-mapped in case the default
 numbering is unsatisfactory.  The drive aliases will be created as
 symbolic links in /dev/disk/by-vdev.
 
-The only currently supported topologies are sas_direct and
-sas_switch.  A multipath mode is supported in which dm-mpath
-devices are handled by examining the first-listed running
-component disk as reported by the
+The currently supported topologies are sas_direct and sas_switch.  A
+multipath mode is supported in which dm-mpath devices are handled by
+examining the first-listed running component disk as reported by the
 .BR multipath (8)
 command.  In multipath mode the configuration file should contain a
 channel definition with the same name for each path to a given
 enclosure.
 
+.BR vdev_id
+also supports creating aliases based on existing udev links in the /dev
+hierarchy using the \fIalias\fR configuration file keyword.  See the
+.BR vdev_id.conf (5)
+man page for details.
+
 .SH OPTIONS
 .TP
 \fB\-c\fR <config_file>