Mounting an NFS File System to Linux ECSs as Root

Prerequisites

• You have checked the type of the OS on each ECS. Different OSs use different commands to install the NFS client.
• You have created an SFS Turbo file system and obtained its shared path.
• At least an ECS that is in the same VPC as the file system is available.
• The IP address of the DNS server for resolving the SFS Turbo file system domain name has been configured on the ECS. SFS Turbo file systems do not require domain name resolution.

Notes and Constraints

This constraint only applies to local paths (mount points) and does not affect other files or directories.

Metadata of the local paths (mount points) cannot be modified. Specifically, the following operations cannot be performed on the local paths' metadata:

- touch: Update file access time and modification time.

- rm: Delete files or directories.

- cp: Replicate files or directories.

- mv: Move files or directories.

- rename: Rename files or directories.

- chmod: Modify permissions on files or directories.

- chown: Change the owners of files or directories.

- chgrp: Change the group of a file or directory.

- ln: Create hard links.

- link: Create hard links.

- unlink: Delete hard links.

The atime, ctime, and mtime attributes of a local path (root directory of the mount point) are the current time. So each time the root directory attribute is queried, the current time of the server is returned.

Procedure

1. Log in to the ECS as user root.
2. Install the NFS client.
   1. Install the NFS client.
      1. Check whether the NFS software package is installed.
         • On CentOS, Red Hat, Oracle Enterprise Linux, SUSE, EulerOS, Fedora, or OpenSUSE, run the following command:

           rpm -qa|grep nfs

         • On Debian or Ubuntu, run the following command:

           dpkg -l nfs-common

         If a command output similar to the following is displayed, the NFS software package has been installed and you can go to 3. If no such command output is displayed, go to 2.a.ii.

         • On CentOS, Red Hat, EulerOS, Fedora, or Oracle Enterprise Linux, the command output is as follows:

           libnfsidmap
           nfs-utils

         • On SUSE or OpenSUSE, the command output is as follows:

           nfsidmap
           nfs-client

         • On Debian or Ubuntu, the command output is as follows:

           nfs-common

      2. Install the NFS software package.
         

         The following commands require that the ECSs be connected to the Internet. Or, the installation will fail.

         • On CentOS, Red Hat, EulerOS, Fedora, or Oracle Enterprise Linux, run the following command:

           sudo yum -y install nfs-utils

         • On Debian or Ubuntu, run the following command:

           sudo apt-get install nfs-common

         • On SUSE or OpenSUSE, run the following command:

           zypper install nfs-client

3. Check whether the domain name in the file system shared path can be resolved.

   nslookup <File system domain name>

   

   • The file system domain name is in the format of xxx.sfsturbo.internal (variable xxx is the file system ID). You can obtain the file system domain name from the file system shared path.
   • If the nslookup command cannot be used, you can run yum install bind-utils to install the bind-utils software package.
   • If the resolution succeeds, go to 4.
   • If the domain name cannot be resolved, configure the DNS server IP address and then mount the file system. For details, see Configuring a DNS Server for Domain Name Resolution.

4. Create a local path for mounting the file system.

   mkdir <Local path>

   

   If any other resources, such as a disk, have been mounted on the local path, create a new path. (NFS clients do not refuse repeated mounts. If there are repeated mounts, information of the last successful mount is displayed.)

5. Mount the file system to the ECSs in the same VPC as the file system. You can mount the file system to Linux ECSs using NFSv3 only.

   Table 1 describes the mount parameters.

   To mount an SFS Turbo file system, run the following command: mount -t nfs -o vers=3,timeo=600,noresvport,nolock,tcp <Shared path> <Local path>

   

   After a mounted ECS is restarted, it loses the file system mount information. You can configure auto mount in the fstab file to ensure that an ECS automatically mounts the file system when it restarts. For details, see Automatically Mounting a File System to Linux ECSs as Root.

   Table 1 Parameters required for mounting file systems

   Parameter	Description
   vers	File system version. Only NFSv3 is supported currently, so the value is fixed to 3.
   timeo	Waiting time before the NFS client retransmits a request. The unit is 0.1 second. The recommended value is 600.
   noresvport	Whether the NFS client uses a new TCP port when it re-establishes a network connection to the NFS server. It is strongly recommended that you specify noresvport, which ensures that your file system remains uninterrupted after a network reconnection or recovery.
   lock/nolock	Whether to use the NLM protocol to lock files on the server. If nolock is specified, the lock is valid only for applications on the same host. It is invalid for applications on any other hosts. nolock is recommended. If this parameter is not specified, lock is used by default. Then, other servers cannot write data to the file system.
   proto	Protocol used by NFS clients to send requests to the server. You can use either UDP or TCP. General Purpose File System does not support UDP. Therefore, you need to set proto to tcp for General Purpose File Systems.
   <Shared path>	For an SFS Turbo Standard-Enhanced, Standard, Performance-Enhanced, or Performance file system, the format is File system IP address:/, for example, 192.168.0.0:/. For an SFS Turbo 20 MB/s/TiB, 40 MB/s/TiB, 125 MB/s/TiB, 250 MB/s/TiB, 500 MB/s/TiB, 1,000 MB/s/TiB, or HPC cache file system, the format is File System domain name:/, for example, xxx.sfsturbo.internal:/. Figure 1 shows an example. NOTE: Variable x is a digit or letter. If the shared path is too long to display completely, you can adjust the column width.
   <Local path>	A local directory on the ECS used to mount the file system, for example, /local_path.

   Figure 1 Shared Path
   

   For more performance optimization mount options, see Table 2. Use commas (,) to separate parameters. A command example is provided as follows:

   mount -t nfs -o vers=3,timeo=600,nolock,rsize=1048576,wsize=1048576,hard,retrans=3,tcp,noresvport,ro,async,noatime,nodiratime <Shared path> <Local path>

   Table 2 Mount options for performance optimization

   Parameter	Description
   rsize	Maximum number of bytes in each read request that the client can receive when reading data from a file on the server. The actual data size is less than or equal to this parameter setting. The value of rsize must be a positive integral multiple of 1024. Specified values less than 1024 are automatically replaced with 4096, and values greater than 1048576 are automatically replaced with 1048576. By default, this parameter is set through a negotiation between the server and the client. You are advised to set this parameter to the maximum value 1048576.
   wsize	Maximum number of bytes in each write request that the client can send when writing data to a file on the server. The actual data size is less than or equal to this parameter setting. The value of wsize must be a positive integral multiple of 1024. Specified values less than 1024 are automatically replaced with 4096, and values greater than 1048576 are automatically replaced with 1048576. By default, this parameter is set through a negotiation between the server and the client. You are advised to set this parameter to the maximum value 1048576.
   soft/hard	soft indicates soft mounts. With soft specified, if an NFS request times out, the client returns an error to the calling program. hard indicates hard mounts. With hard specified, if an NFS request times out, the client continues to request until the request is successful. The default value is hard.
   retrans	Number of retransmission times before the client returns an error. The recommended value is 1.
   tcp/udp	If mountproto is not specified, the client will mount the file system using UDP first. If the UDP network is not connected, the client will mount the file system using TCP after freezing for several seconds. The UDP port used for mounting is currently not enabled in the inbound rule of the security group, so you need to specify tcp when mounting the file system.
   ro/rw	ro: indicates that the file system is mounted as read-only. rw: indicates that the file system is mounted as read/write. The default value is rw. If this parameter is not specified, the file system will be mounted as read/write.
   noresvport	Whether the NFS client uses a new TCP port when it re-establishes a network connection to the NFS server. It is strongly recommended that you specify noresvport, which ensures that your file system remains uninterrupted after a network reconnection or recovery.
   sync/async	sync indicates that data is written to the server immediately. async indicates that data is first written to the cache and then to the server. async is recommended. Synchronous writes require that an NFS server returns a success message after all data is written to the server, which brings long latency.
   noatime	If you do not need to record the file access time, set this parameter. This prevents overheads caused by frequent access to modify the time.
   nodiratime	If you do not need to record the directory access time, set this parameter. This prevents overheads caused by frequent access to modify the time.

   

   You are advised to use the default values for the parameters with no usage recommendations provided.

6. View the mounted file system.

   mount -l

   If the command output contains the following information, the file system has been mounted:

   <Shared path> on </local_path> type nfs (rw,vers=3,timeo=600,nolock,addr=)

7. Check that you can access the file system on the ECSs to read or write data.
   

   The maximum size of a file that can be written to an SFS Turbo file system is 32 TB, and that for an SFS Turbo Enhanced file system is 320 TB.