Merge pull request #4443 from MicrosoftDocs/FromPublicRepo

Confirm merge from FromPublicRepo to master to sync with https://github.com/MicrosoftDocs/sql-docs (branch live)

Author: v-alje

docs/database-engine/availability-groups/windows/upgrading-always-on-availability-group-replica-instances.md

@@ -39,7 +39,7 @@ ms.workload: "On Demand"
 -   [Hardware and Software Requirements for Installing SQL Server 2016](../../../sql-server/install/hardware-and-software-requirements-for-installing-sql-server.md):  Review the software requirements for installing [!INCLUDE[ssCurrent](../../../includes/sscurrent-md.md)]. If additional software is required, install it on each node before you begin the upgrade process to minimize any downtime.  
 
 > [!NOTE]  
->  Mixing versions of SQL Server in the same AG is not supported. To migrate to a new version using availablity groups, the only supported method is a distributed availability group which is in SQL Server 2016 Enterprise Edition or later.
+>  Mixing versions of SQL Server in the same AG is not supported outside of a rolling upgrade which upgrades the replicas in place. This means a higher version of SQL Server cannot be added as a new replica to an existing AG. For example, a SQL Server 2017 replica cannot be added to an existing SQL Server 2016 AG. To migrate to a new version of SQL Server using availablity groups, the only supported method is a distributed availability group which is in SQL Server 2016 Enterprise Edition or later.
 
 ## Rolling Upgrade Best Practices for Always On Availability Groups  
  The following best practices should be observed when performing server upgrades or updates in order to minimize downtime and data loss for your availability groups:  

docs/linux/sql-server-linux-shared-disk-cluster-red-hat-7-configure.md

@@ -209,7 +209,7 @@ For additional information about using NFS, see the following resources:
 1.  **On the primary node only**, save the database files to a temporary location.The following script, creates a new temporary directory, copies the database files to the new directory, and removes the old database files. As SQL Server runs as local user mssql, you need to make sure that after data transfer to the mounted share, local user has read-write access to the share. 
 
    ``` 
-   $ su mssql
+   $ sudo su mssql
    $ mkdir /var/opt/mssql/tmp
    $ cp /var/opt/mssql/data/* /var/opt/mssql/tmp
    $ rm /var/opt/mssql/data/*
@@ -235,9 +235,9 @@ For additional information about using NFS, see the following resources:
 1.  Copy the database and log files that you saved to `/var/opt/mssql/tmp` to the newly mounted share `/var/opt/mssql/data`. This only needs to be done **on the primary node**. Make sure that you give read write permissions to 'mssql' local user.
 
    ``` 
-   $ chown mssql /var/opt/mssql/data
-   $ chgrp mssql /var/opt/mssql/data
-   $ su mssql
+   $ sudo chown mssql /var/opt/mssql/data
+   $ sudo chgrp mssql /var/opt/mssql/data
+   $ sudo su mssql
    $ cp /var/opt/mssql/tmp/* /var/opt/mssql/data/
    $ rm /var/opt/mssql/tmp/*
    $ exit
@@ -260,8 +260,8 @@ At this point both instances of SQL Server are configured to run with the databa
 
    ```bash
    sudo touch /var/opt/mssql/secrets/passwd
-   sudo echo '<loginName>' >> /var/opt/mssql/secrets/passwd
-   sudo echo '<loginPassword>' >> /var/opt/mssql/secrets/passwd
+   echo '<loginName>' | sudo tee -a /var/opt/mssql/secrets/passwd
+   echo '<loginPassword>' | sudo tee -a /var/opt/mssql/secrets/passwd
    sudo chown root:root /var/opt/mssql/secrets/passwd 
    sudo chmod 600 /var/opt/mssql/secrets/passwd    
    ```

docs/linux/sql-server-linux-shared-disk-cluster-red-hat-7-operate.md

@@ -179,7 +179,7 @@ View the resource agent logs at `/var/log/cluster/corosync.log`
     sudo pcs    cluster node add <nodeName3> 
     ```
 
-    The following example ads a node named **vm3** to the cluster.
+    The following example adds a node named **vm3** to the cluster.
 
     ```bash
     sudo pcs    cluster auth  

docs/relational-databases/backup-restore/sql-server-backup-to-url.md

@@ -351,7 +351,7 @@ After succesfully running the script, copy the `CREATE CREDENTIAL` command to a
    (SELECT * FROM sys.credentials   
    WHERE name = 'https://<mystorageaccountname>.blob.core.windows.net/<mystorageaccountcontainername>')  
    CREATE CREDENTIAL [https://<mystorageaccountname>.blob.core.windows.net/<mystorageaccountcontainername>] 
-      WITH IDENTITY = 'SHARED ACCESS IGNATURE',  
+      WITH IDENTITY = 'SHARED ACCESS SIGNATURE',  
       SECRET = '<SAS_TOKEN>';  
    ```  
 

docs/t-sql/statements/backup-transact-sql.md

@@ -98,7 +98,7 @@ BACKUP LOG { database_name | @database_name_var }
  {  
    { logical_device_name | @logical_device_name_var }   
  | { DISK | TAPE | URL} =   
-     { 'physical_device_name' | @physical_device_name_var }  
+     { 'physical_device_name' | @physical_device_name_var | NUL }  
  }   
   
 <MIRROR TO clause>::=  
@@ -193,7 +193,7 @@ FILEGROUP = { logical_filegroup_name | @logical_filegroup_name_var }
  Is the logical name of a filegroup or a variable whose value equates to the logical name of a filegroup that is to be included in the backup. Under the simple recovery model, a filegroup backup is allowed only for a read-only filegroup.  
 
 > [!NOTE]  
->  Consider using file backups when the database size and performance requirements make a database backup impractical.  
+>  Consider using file backups when the database size and performance requirements make a database backup impractical. The NUL device can be used to test the performance of backups, but should not be used in production environments.
   
  *n*  
  Is a placeholder that indicates that multiple files and filegroups can be specified in a comma-separated list. The number is unlimited. 
@@ -226,15 +226,20 @@ TO \<backup_device> [ **,**...*n* ]
  { *logical_device_name* | **@***logical_device_name_var* }  
  Is the logical name of the backup device to which the database is backed up. The logical name must follow the rules for identifiers. If supplied as a variable (@*logical_device_name_var*), the backup device name can be specified either as a string constant (@*logical_device_name_var***=** logical backup device name) or as a variable of any character string data type except for the **ntext** or **text** data types.  
 
- { DISK | TAPE | URL} **=** { **'***physical_device_name***'** | **@***physical_device_name_var* }  
- Specifies a disk file or tape device, or a Windows Azure Blob storage service. The URL format is used for creating backups to the Windows Azure storage service. For more information and examples, see [SQL Server Backup and Restore with Microsoft Azure Blob Storage Service](../../relational-databases/backup-restore/sql-server-backup-and-restore-with-microsoft-azure-blob-storage-service.md). For a tutorial, see [Tutorial: SQL Server Backup and Restore to Windows Azure Blob Storage Service](~/relational-databases/tutorial-sql-server-backup-and-restore-to-azure-blob-storage-service.md).  
+ { DISK | TAPE | URL} **=** { **'***physical_device_name***'** | **@***physical_device_name_var* | NUL }  
+ Specifies a disk file or tape device, or a Windows Azure Blob storage service. The URL format is used for creating backups to the Windows Azure storage service. For more information and examples, see [SQL Server Backup and Restore with Microsoft Azure Blob Storage Service](../../relational-databases/backup-restore/sql-server-backup-and-restore-with-microsoft-azure-blob-storage-service.md). For a tutorial, see [Tutorial: SQL Server Backup and Restore to Windows Azure Blob Storage Service](~/relational-databases/tutorial-sql-server-backup-and-restore-to-azure-blob-storage-service.md). 
+
+[!NOTE] 
+ The NUL disk device will discard all information sent to it and should only be used for testing. This is not for production use.
 
 > [!IMPORTANT]  
 >  With [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] SP1 CU2 until [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)], you can only backup to a single device when backing up to URL. In order to backup to multiple devices when backing up to URL, you must use [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] through [!INCLUDE[ssCurrent](../../includes/sscurrent-md.md)] and you must use Shared Access Signature (SAS) tokens. For examples creating a Shared Access Signature, see [SQL Server Backup to URL](../../relational-databases/backup-restore/sql-server-backup-to-url.md) and [Simplifying creation of SQL Credentials with Shared Access Signature (SAS) tokens on Azure Storage with Powershell](http://blogs.msdn.com/b/sqlcat/archive/2015/03/21/simplifying-creation-sql-credentials-with-shared-access-signature-sas-keys-on-azure-storage-containers-with-powershell.aspx).  
   
 **URL applies to**: [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] ([!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] SP1 CU2 through [!INCLUDE[ssCurrent](../../includes/sscurrent-md.md)]).  
 
  A disk device does not have to exist before it is specified in a BACKUP statement. If the physical device exists and the INIT option is not specified in the BACKUP statement, the backup is appended to the device.  
+ 
+ The NUL device will discard all input sent to this file, however the backup will still mark all pages as backed up.
 
  For more information, see [Backup Devices &#40;SQL Server&#41;](../../relational-databases/backup-restore/backup-devices-sql-server.md).