NFS Client Time Synchronization via Temporary File Timestamp

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Solution Overview

Problem

The system time of a client connected to an NFS server may differ from the NFS server's time, causing time-dependent build steps to fail due to the NFS server's time being ahead from the client's perspective, necessitating a reliable timing source.

Innovation Solution

A client sets its system time by creating a zero-length file on the NFS server, reading the last-modified time attribute, and adjusting its system time accordingly before deleting the file, utilizing temporary user ID changes or child processes to perform these operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the client uses its own local time for build steps, then the build process can proceed without waiting for time synchronization, but time-dependent build steps will fail because the NFS server's time is ahead from the client's perspective

Engineering Contradiction:

Improvebuild process continuityVSAvoidtime-dependent build step success

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The client performs time synchronization with the NFS server before executing build steps. By reading the server's current time and adjusting the local time accordingly, the system ensures that time-dependent operations will succeed without failure, while maintaining build process continuity.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If the client synchronizes time with the NFS server by creating and reading a file, then accurate time synchronization is achieved, but additional file operations and user ID changes are required increasing complexity

Engineering Contradiction:

Improvetime synchronization accuracyVSAvoidtime setting process complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent uses a temporary file as an intermediary to transfer time information from the NFS server to the client. The file serves as a medium that carries the server's current time, allowing the client to read and process this time information without requiring direct time synchronization protocols or complex communication mechanisms.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The NFS server automatically updates the timestamp of the file it creates or maintains, eliminating the need for the server to actively send time information. The client simply needs to read the file's timestamp attribute, and the server's normal file operations naturally provide the time synchronization service.

Inventive Principle:

Principle #25Self-service

3Loss of information

If the client reads the last-modified time attribute of a file on the NFS server, then the client can obtain the server's time information, but the file must be temporarily created and then deleted adding operational steps

Engineering Contradiction:

Improveserver time information accessVSAvoidtime retrieval operation simplicity

Core Design Contradiction:

Loss of informationVSEase of operation

Solution Approach 1:

The patent uses a temporary file that is created solely for the purpose of transferring time information and then immediately deleted. This disposable file serves as a convenient vehicle for obtaining the server's time through its timestamp attribute, and its temporary nature means it does not leave residual data or require long-term management.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS8380662B2Setting time from a NFS server

Publication Date: 2013.02.19 RED HAT INC

AI summary

A system time of a client is set from a network file system (NFS) server. In one embodiment, the client creates a file on the (NFS) server and reads the last-modified time attribute of the file. The client adjusts its system time accordingly based on the last-modified time attribute of the file. The file is then deleted from the NFS server.