Distributed Network File System (DNFS)

This project implements a Distributed Network File System (DNFS) with three main components: a Naming Server, multiple Storage Servers, and Clients. DNFS supports distributed file storage, access control, replication for fault tolerance, and advanced file operations such as streaming and sentence-level editing.

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Architecture

• Naming Server (NM): Central directory and controller. Manages file indexing (hash maps), client authentication, ACLs, storage server heartbeats, and replication logic.
• Storage Server (SS): Handles file storage and data operations. Manages local file parsing, lazy-loading, and synchronization with the NM.
• Client: User interface for interacting with the file system. Communicates with the NM for file locations and connects to SS for file operations.

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Key Features

• Distributed File Operations: Create, read, delete, and list files across servers.
• Sentence-Level Editing: Update specific sentences in a file with WRITE and revert with UNDO.
• Streaming: Stream file content with controlled delays.
• Access Control:
  • Ownership and ACL-based permissions (Read/Write).
  • Request-approval workflow for access to non-owned files.
• Fault Tolerance & Replication:
  • Automatic file replication to backup servers.
  • Primary-backup failover with automatic client redirection.
  • Heartbeat monitoring for server failure detection.
• Recycle Bin: Soft-delete with garbage collection after a configurable timeout (default 60 seconds).
• Checkpoints: Create and revert to file snapshots.
• Remote Execution: Execute shell scripts on storage servers.

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Prerequisites

• GCC (C99 or later)
• POSIX Threads (pthreads)
• Linux/Unix environment (uses system calls like mkdir, remove, popen)

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Installation

Compile the project using the provided Makefile:

make all

This generates three executables: nameserver_exe, storageserver_exe, and client_exe.

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Usage

1. Start the Naming Server

The Naming Server listens for clients on port 8080 and Storage Servers on port 8081.

./nameserver_exe

2. Start Storage Servers

Each Storage Server requires specific arguments:

./storageserver_exe <nm_ip> <nm_port> <advertise_ip> <client_port> <storage_dir> <is_primary>

• nm_port: Use 8081.
• is_primary: 1 for primary, 0 for backup.

3. Start the Client

./client_exe

Follow prompts to enter the Naming Server IP and your username.

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Client Commands

Command	Description
VIEW [-a] [-l]	View all files (optionally list all/detailed info)
CREATE <filename>	Create a new file
READ <filename>	Read file content
WRITE <filename> <sentence_no>	Edit or append a sentence
UNDO <filename>	Revert the last write
STREAM <filename>	Stream file content
DELETE [-F] <filename>	Soft delete (use -F for hard delete)
RESTORE <filename>	Restore from Recycle Bin
VIEWTRASH	List files in Recycle Bin
CHECKPOINT <file> <tag>	Create a named snapshot
REVERT <file> <tag>	Revert to a checkpoint
REQACCESS <file> <R/W>	Request file access
APPROVE <file> <user>	Approve access request (Owner only)
EXEC <filename>	Execute a shell script on server
exit	Disconnect from the system

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Configuration

System limits and constants are defined in networking.h:

• PAYLOAD_SIZE: 4096 bytes
• MAX_CLIENTS: 100
• MAX_SS: 10
• MAX_REPLICAS: 1

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License

This project is licensed under the MIT License.