LWM-Linux/08 - Advanced Linux Administration/Network File Systems (NFS).md

etwork File Systems (NFS)

Network File System (NFS) Overview:

NFS is a distributed file system protocol that allows a user on a client computer to access files over a network in a manner similar to how local storage is accessed. NFS was originally developed by Sun Microsystems in 1984 and has since become a widely used protocol for file sharing in Unix-like operating systems.

Key Features of NFS:

• 1. Transparent access to remote files
• 2. Support for heterogeneous environments
• 3. Stateless protocol (versions 2 and 3)
• 4. Caching for improved performance
• 5. User authentication and access control

NFS Versions:

• 1. NFSv2 (1989): The first widely used version
• 2. NFSv3 (1995): Improved performance and added features
• 3. NFSv4 (2000): Major revision with enhanced security and internet-friendly features
• 4. NFSv4.1 (2010): Added parallel NFS (pNFS) for improved scalability
• 5. NFSv4.2 (2016): Added server-side copy and space reservation

NFS Architecture:

NFS follows a client-server model:

• 1. NFS Server: Exports file systems to be shared
• 2. NFS Client: Mounts the exported file systems
• 3. RPC (Remote Procedure Call): Facilitates communication between client and server

NFS Components:

• 1. MOUNT protocol: Handles the mounting of file systems
• 2. NFS protocol: Manages file and directory operations
• 3. Portmapper/RPCBIND: Maps RPC program numbers to network port numbers
• 4. NFS Daemon (nfsd): Handles client requests on the server
• 5. Lock Manager (lockd): Manages file locking
• 6. Status Monitor (statd): Provides crash and recovery functions

NFS Operation:

• 1. Server exports file systems
• 2. Client discovers available exports
• 3. Client mounts desired file system
• 4. Client accesses files using NFS protocol

Security Considerations:

• 1. Authentication: Kerberos (NFSv4), AUTH_SYS (older versions)
• 2. Authorization: Access control lists (ACLs) or traditional Unix permissions
• 3. Encryption: RPCSEC_GSS (NFSv4)
• 4. Firewall configuration: Proper port management

Performance Tuning:

• 1. Adjust read and write buffer sizes
• 2. Optimize network settings (MTU, TCP window size)
• 3. Use appropriate mount options (e.g., rsize, wsize)
• 4. Implement caching strategies

Common NFS Commands:

• 1. exportfs: Maintain table of exported file systems
• 2. showmount: Display mount information for an NFS server
• 3. mount/umount: Mount and unmount NFS shares
• 4. nfsstat: Display NFS statistics

Troubleshooting NFS:

• 1. Check network connectivity
• 2. Verify NFS services are running
• 3. Review server logs (/var/log/messages, /var/log/syslog)
• 4. Use tcpdump or Wireshark for packet analysis
• 5. Test with different NFS versions or mount options

NFS Alternatives:

• 1. Samba (SMB/CIFS): Better for Windows integration
• 2. AFS (Andrew File System): Designed for large-scale distributed computing
• 3. GlusterFS: Scalable network filesystem
• 4. Ceph: Distributed object store and file system

Best Practices:

• 1. Use NFSv4 when possible for improved security and performance
• 2. Implement proper access controls and user mapping
• 3. Regularly update NFS software to address security vulnerabilities
• 4. Monitor NFS performance and adjust settings as needed
• 5. Implement redundancy and failover mechanisms for critical deployments

NFS in Modern Environments:

• 1. Container orchestration: NFS can be used as persistent storage for Kubernetes
• 2. Cloud computing: Many cloud providers offer NFS-compatible file storage services
• 3. Hybrid environments: NFS can bridge on-premises and cloud storage