# Mounting a file share on an Amazon EC2 Linux instance
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You can mount an FSx for Windows File Server file share on an Amazon EC2 Linux instance that is either joined to your Active Directory or not joined to access your FSx for Windows File Server file system.

**Note**  
The following commands specify parameters such as SMB protocol, caching, and read and write buffer size as examples only. Parameter choices for the Linux `cifs` command, as well as the Linux kernel version used, can impact throughput and latency for network operations between the client and the Amazon FSx file system. For more information, see `cifs` documentation for the Linux environment you are using.
Linux clients do not support automatic DNS-based failover. For more information, see [Failover experience on Linux clients](high-availability-multiAZ.md#linux-failover).

## To mount a file share on an Amazon EC2 Linux instance joined to an Active Directory
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1. If you don't already have a running EC2 Linux instance joined to your Microsoft Active Directory, see [Manually join a Linux instance](https://docs.aws.amazon.com/directoryservice/latest/admin-guide/join_linux_instance.html) in the *AWS Directory Service Administration Guide* for the instructions to do so. 

1. Connect to your EC2 Linux instance. For more information, see [Connect to your Linux instance](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/AccessingInstances.html) in the *Amazon EC2 User Guide*.

1. Run the following command to install the `cifs-utils` package. This package is used to mount network file systems like Amazon FSx on Linux.

   ```
   $ sudo yum install cifs-utils
   ```

1. Create the mount point directory **/mnt/fsx**. This is where you will mount the Amazon FSx file system.

   ```
   $ sudo mkdir -p /mnt/fsx
   ```

1. Authenticate with kerberos using the following command.

   ```
   $ kinit
   ```

1. Mount the file share with the following command.

   ```
   $ sudo mount -t cifs //{{file_system_dns_name}}/{{file_share}} {{mount_point}} --verbose -o vers={{SMB_version}},sec=krb5,cruid={{ad_user}},rsize={{CIFSMaxBufSize}},wsize={{CIFSMaxBufSize}},cache=none,ip={{preferred-file-server-Ip}}
   ```

    You can find the DNS name on the [Amazon FSx console](https://console.aws.amazon.com/fsx) by choosing **Windows File Server**, **Network & security**. Or, you can find them in the response of `CreateFileSystem` or `DescribeFileSystems` API operation.
   + For a Single-AZ file system joined to an AWS Managed Microsoft Active Directory, the DNS name looks like the following.

     ```
     fs-0123456789abcdef0.{{ad-domain}}.com
     ```
   + For a Single-AZ file system joined to a self-managed Active Directory, and any Multi-AZ file system, the DNS name looks like the following.

     ```
     amznfsxaa11bb22.{{ad-domain}}.com
     ```

   Replace `{{CIFSMaxBufSize}}` with the largest value allowed by your kernel. Run the following command to get this value.

   ```
   $ modinfo cifs | grep CIFSMaxBufSize
   parm:           CIFSMaxBufSize:Network buffer size (not including header). Default: 16384 Range: 8192 to 130048 (uint)
   ```

   The output shows that the maximum buffer size is 130048.

1. Verify that the file system is mounted by running the following command, which returns only file systems of the Common Internet File System (CIFS) type.

   ```
   $ mount -l -t cifs
   //fs-0123456789abcdef0/share on /mnt/fsx type cifs (rw,relatime,vers={{SMB_version}},sec=krb5,cache={{cache_mode}},username=user1@CORP.NETWORK.COM,uid=0,noforceuid,gid=0,noforcegid,addr=192.0.2.0,file_mode=0755,dir_mode=0755,soft,nounix,serverino,mapposix,rsize=1048576,wsize=1048576,echo_interval=60,actimeo=1)
   ```

The mount command used in this procedure does the following at the given points:
+ `//{{file_system_dns_name}}/{{file_share}}` – Specifies the DNS name and share of the file system to mount.
+ {{mount\_point}} – The directory on the EC2 instance that you are mounting the file system to.
+ `-t cifs vers={{SMB_version}}` – Specifies the type of file system as CIFS and the SMB protocol version. Amazon FSx for Windows File Server supports SMB versions 2.0 through 3.1.1.
+ `sec=krb5` – Specifies to use Kerberos version 5 for authentication.
+ `cache={{cache_mode}}` – Sets the cache mode. This option for CIFS cache can impact performance, and you should test which settings work best (and review Linux documentation) for your kernel and workload. Options `strict` and `none` are recommended, because `loose` can cause data inconsistency due to the looser protocol semantics.
+ `cruid={{ad_user}}` – Sets the uid of the owner of the credentials cache to the AD directory administrator.
+ `{{/mnt/fsx}}` – Specifies the mount point for the Amazon FSx file share on your EC2 instance.
+ `rsize={{CIFSMaxBufSize}},wsize={{CIFSMaxBufSize}}` – Specifies the read and write buffer size as the maximum allowed by the CIFS protocol. Replace `{{CIFSMaxBufSize}}` with the largest value allowed by your kernel. Determine the `CIFSMaxBufSize` by running the following command.

  ```
  $ modinfo cifs | grep CIFSMaxBufSize
  parm:           CIFSMaxBufSize:Network buffer size (not including header). Default: 16384 Range: 8192 to 130048 (uint)
  ```

  The output shows that the maximum buffer size is 130048.
+ `ip={{preferred-file-server-Ip}}` – Sets the destination IP address to that of the file system's preferred file server.

  You can retrieve the file system's preferred file server IP address as follows:
  + Using the Amazon FSx console, on the **Network & security** tab of the **File system details** page.
  + In the response of the `describe-file-systems` CLI command or the equivalent [DescribeFileSystems](https://docs.aws.amazon.com/fsx/latest/APIReference/API_DescribeFileSystems.html) API command.