Migrate ZFS-* message descriptions (#49)

Prerequisite for changing the URLs in the command outputs from
zfsonlinux.org to openzfs.github.io/openzfs-docs/

Signed-off-by: Ryan Moeller <ryan@iXsystems.com>

docs/msg/ZFS-8000-4J/index.rst

@@ -0,0 +1,133 @@
+..
+   CDDL HEADER START
+
+   The contents of this file are subject to the terms of the
+   Common Development and Distribution License (the "License").
+   You may not use this file except in compliance with the License.
+
+   You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+   or http://www.opensolaris.org/os/licensing.
+   See the License for the specific language governing permissions
+   and limitations under the License.
+
+   When distributing Covered Code, include this CDDL HEADER in each
+   file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+   If applicable, add the following below this CDDL HEADER, with the
+   fields enclosed by brackets "[]" replaced with your own identifying
+   information: Portions Copyright [yyyy] [name of copyright owner]
+
+   CDDL HEADER END
+
+   Portions Copyright 2007 Sun Microsystems, Inc.
+
+.. highlight:: none
+
+Message ID: ZFS-8000-4J
+=======================
+
+Corrupted device label in a replicated configuration
+----------------------------------------------------
+
++-------------------------+--------------------------------------------------+
+| **Type:**               | Error                                            |
++-------------------------+--------------------------------------------------+
+| **Severity:**           | Major                                            |
++-------------------------+--------------------------------------------------+
+| **Description:**        | A device could not be opened due to a missing or |
+|                         | invalid device label.                            |
++-------------------------+--------------------------------------------------+
+| **Automated Response:** | A hot spare will be activated if available.      |
++-------------------------+--------------------------------------------------+
+| **Impact:**             | The pool is no longer providing the configured   |
+|                         | level of replication.                            |
++-------------------------+--------------------------------------------------+
+
+.. rubric:: Suggested Action for System Administrator
+
+.. rubric:: For an active pool:
+
+If this error was encountered while running ``zpool import``, please
+see the section below.  Otherwise, run ``zpool status -x`` to determine
+which pool has experienced a failure:
+
+::
+
+   # zpool status -x
+     pool: test
+    state: DEGRADED
+   status: One or more devices could not be used because the label is missing or
+           invalid.  Sufficient replicas exist for the pool to continue
+           functioning in a degraded state.
+   action: Replace the device using 'zpool replace'.
+      see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-4J
+    scrub: none requested
+   config:
+
+           NAME                  STATE     READ WRITE CKSUM
+           test                  DEGRADED     0     0     0
+             mirror              DEGRADED     0     0     0
+               c0t0d0            ONLINE       0     0     0
+               c0t0d1            FAULTED      0     0     0  corrupted data
+
+   errors: No known data errors
+
+If the device has been temporarily detached from the system, attach
+the device to the system and run ``zpool status`` again.  The pool
+should automatically detect the newly attached device and resume
+functioning.
+
+If the device is no longer available, it can be replaced using ``zpool 
+replace``:
+
+::
+
+   # zpool replace test c0t0d1 c0t0d2
+
+If the device has been replaced by another disk in the same physical
+slot, then the device can be replaced using a single argument to the
+``zpool replace`` command:
+
+::
+
+   # zpool replace test c0t0d1
+
+ZFS will begin migrating data to the new device as soon as the
+replace is issued.  Once the resilvering completes, the original
+device (if different from the replacement) will be removed, and the
+pool will be restored to the ONLINE state.
+
+.. rubric:: For an exported pool:
+
+If this error is encountered while running ``zpool import``, the pool
+can be still be imported despite the failure:
+
+::
+
+   # zpool import
+     pool: test
+       id: 5187963178597328409
+    state: DEGRADED
+   status: One or more devices contains corrupted data.  The fault tolerance of
+           the pool may be compromised if imported.
+   action: The pool can be imported using its name or numeric identifier.
+      see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-4J
+   config:
+
+           test              DEGRADED
+             mirror          DEGRADED
+               c0t0d0        ONLINE
+               c0t0d1        FAULTED   corrupted data
+
+To import the pool, run ``zpool import``:
+
+::
+
+   # zpool import test
+
+Once the pool has been imported, the damaged device can be replaced
+according to the above procedure.
+
+.. rubric:: Details
+
+The Message ID: ``ZFS-8000-4J`` indicates a device which was unable
+to be opened by the ZFS subsystem.