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-8000-2Q/index.rst

@@ -0,0 +1,134 @@
+..
+   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-8000-2Q
+=======================
+
+Missing device in replicated configuration
+------------------------------------------
+
++-------------------------+--------------------------------------------------+
+| **Type:**               | Error                                            |
++-------------------------+--------------------------------------------------+
+| **Severity:**           | Major                                            |
++-------------------------+--------------------------------------------------+
+| **Description:**        | A device in a replicated configuration could not |
+|                         | be opened.                                       |
++-------------------------+--------------------------------------------------+
+| **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 opened.  Sufficient replicas exist for
+           the pool to continue functioning in a degraded state.
+   action: Attach the missing device and online it using 'zpool online'.
+      see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-2Q
+    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  cannot open
+
+   errors: No known data errors
+
+Determine which device failed to open by looking for a FAULTED device
+with an additional 'cannot open' message.  If this device has been
+inadvertently removed from the system, attach the device and bring it
+online with ``zpool online``:
+
+::
+
+   # zpool online test c0t0d1
+
+If the device is no longer available, the device can be replaced
+using the ``zpool replace`` command:
+
+::
+
+   # 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
+
+Existing data will be resilvered to the new device.  Once the
+resilvering completes, the device will be removed from the pool.
+
+.. rubric:: For an exported pool:
+
+If this error is encountered during a ``zpool import``, it means that
+one of the devices is not attached to the system:
+
+::
+
+   # zpool import
+     pool: test
+       id: 10121266328238932306
+    state: DEGRADED
+   status: One or more devices are missing from the system.
+   action: The pool can be imported despite missing or damaged devices.  The
+           fault tolerance of the pool may be compromised if imported.
+      see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-2Q
+   config:
+
+           test              DEGRADED
+             mirror          DEGRADED
+               c0t0d0        ONLINE
+               c0t0d1        FAULTED   cannot open
+
+Unlike when the pool is active on the system, the device cannot be
+replaced while the pool is exported.  If the device can be attached to
+the system, attach the device and run ``zpool import`` again.
+
+Alternatively, the pool can be imported as-is, though it will be
+placed in the DEGRADED state due to a missing device.  The device will
+be marked as UNAVAIL. Once the pool has been imported, the missing
+device can be replaced as described above.
+
+.. rubric:: Details
+
+The Message ID: ``ZFS-8000-2Q`` indicates a device which was unable
+to be opened by the ZFS subsystem.