mount

mount is a command-line utility in Unix-like operating systems used to attach filesystems to the directory tree. It supports a wide range of filesystem types including local filesystems (like ext4, xfs) and network filesystems such as NFS.

Basic Syntax

mount [OPTIONS] DEVICE MOUNT_POINT

• DEVICE: The storage device, partition, or network share to be mounted.

• MOUNT_POINT: The directory where the filesystem will be attached.

• OPTIONS: Various flags to modify mount behavior.

Common Options

• -t type: Specifies the filesystem type (e.g., ext4, nfs, vfat).

• -o options: A comma-separated list of mount options.

• -v: Verbose mode; displays detailed output.

NFS Mount Options

When mounting an NFS share, you can fine-tune various options to optimize performance and reliability. Below are some commonly used NFS mount options:

Basic Options

• rw/ro:

  • rw: Mount the share as read-write.

  • ro: Mount the share as read-only.

• vers=: Specifies the NFS protocol version (e.g., vers=3 or vers=4).

Performance Options

• rsize and wsize: Define the maximum chunk sizes (in bytes) for read and write operations.

  • Example: rsize=8192,wsize=8192

• async: Allows asynchronous writes, which can improve performance at the cost of data integrity in the event of a crash.

• sync: Forces synchronous writes for improved data integrity, though it may reduce performance.

Reliability Options

• hard vs. soft:

  • hard: The client retries indefinitely if the server becomes unresponsive (recommended for data integrity).

  • soft: The client will eventually time out, which can lead to errors if the server remains unavailable.

• intr: Allows NFS requests to be interrupted if the server is unresponsive, which is useful with hard mounts.

• timeo: Sets the timeout (in tenths of a second) for NFS requests.

  • Example: timeo=14

• retrans: Specifies the number of times to retry a request before giving up.

  • Example: retrans=3

Locking Options

• nolock: Disables NFS file locking. Useful if file locking is managed by another mechanism.

Background and Foreground Options

• bg: If the initial mount attempt fails, retry in the background.

• fg: Forces the mount operation to run in the foreground (default behavior).

Example: Mounting an NFS Share

To mount an NFS share exported from a server with IP address 192.168.1.100 (exporting /export/shared) to a local mount point /mnt/shared, you might use:

mount -t nfs -o rw,vers=4,rsize=8192,wsize=8192,hard,intr,timeo=14,retrans=3 192.168.1.100:/export/shared /mnt/shared

This command mounts the NFS share with the following options:

• Read-Write (rw)

• Using NFS Version 4 (vers=4)

• Optimized Read/Write Sizes (rsize=8192,wsize=8192)

• Hard Mount with Interrupts Enabled (hard,intr)

• Custom Timeout and Retransmission Settings (timeo=14,retrans=3)

Conclusion

The mount command is essential for attaching both local and network filesystems. When dealing with NFS, a variety of mount options are available to customize performance, reliability, and security. By using options like rsize, wsize, hard, intr, timeo, and vers, administrators can optimize NFS mounts to suit their specific environment.