NFS

1. NFS Presented by: mohamad amin Rastgoo Published under Term of GPL

2. What is file System? • A disk drive by itself provides a place to store data, and nothing more. In fact, by itself, the only way to access data on a hard drive is by either specifying the data's physical location (in terms of cylinder, head, and sector), or by its logical location (the 65,321st block) on the disk. • What is needed is a way to more easily keep track of things stored on hard drives; a way of filling information in an easilyaccessible way. • That is the role of the file system. Published under Term of GPL

3. An Overview of File Systems • File systems, as the name implies, treat different sets of information as files. Each file is separate from every other. Over and above the information stored within it, each file includes additional information: • The file's name • The file's access permissions • The time and date of the file's creation, access, and modification. • While file systems in the past have included no more complexity than that already mentioned, presentday file systems include mechanisms to make it easier to group related files together. The most commonly used mechanism is the directory. Often implemented as a special type of file, directories make it possible to create hierarchical structures of files and directories. Published under Term of GPL

4. What is NFS? • As the name implies, the Network File System (more commonly known as NFS) is a file system that may be accessed via a network connection. • The Network File System (NFS) was developed to allow machines to mount a disk partition on a remote machine as if it were on a local hard drive. This allows for fast, seamless sharing of files across a network With other file systems, the storage device must be directly attached to the local system. However, with NFS this is not a requirement, making possible a variety of different configurations, from centralized file system servers, to entirely diskless computer systems • However, unlike the other file systems discussed here, NFS does not dictate a specific ondisk format. Instead, it relies on the server operating system's native file system support to control the actual I/O to local disk drive(s). NFS then makes the file system available to any operating system running a compatible NFS client. Published under Term of GPL

5. NFS & SAMBA • Samba uses the SMB protocol to share files and printers across a network connection. • Operating systems that support this protocol include Microsoft Windows, OS/2, and Linux • From a basic point of view, NFS and Samba are very similar. Both have a client and server application. Both allow a server to share files with clients. Both have clients and servers on almost every platform. The big difference is the Windows PCs have Samba-compatible clients and servers as part of their default network support and Windows requires third party software to support NFS. Conversely, UNIX systems usually come with and use NFS by default with Samba being used to provide file sharing with Windows PCs. • SMB is a protocol used by the Microsoft Windows operating system to share files on a network. NFS is a protocol used primarily on UNIX platforms for sharing Published under Term of GPL

6. Why Use NFS? • NFS is useful for sharing directories of files between multiple users on the same network. • For example, a group of users working on the same project can have access to the files for that project using a shared directory of the NFS file system (commonly known as an NFS share) mounted in the directory /myproject. To access the shared files, the user goes into the /myproject directory on his machine. There are no passwords to enter or special commands to remember. Users work as if the directory is on their local machine Published under Term of GPL

7. Useful usage • It can be used for Networked Backups: • The theory of NFS backup is relatively simple: mount each host to the NFS • server, write a .tar backup script, and check that the following permission • sets conform on both machines: • 1. Read Write access. • 2. Mount permissions. • 3. GID/UID. Published under Term of GPL

8. Protocols • There are several revisions—or protocols—of NFS. Version 3 of NFS (NFSv3) is rapidly becoming the default version on most Linux systems. This version is available in the latest Linux 2.2 and 2.4 kernels • Version 4 in under develop and going to remove lacks: • NFS Versions 2 and 3 are stateless protocols, but NFS Version 4 introduces state. • NFS Version 4 introduces support for byterange locking and share reservation. • NFS Version 4 introduces file delegation. • NFS Version 4 uses compound RPCs. • NFS Version 4 specifies a number of sophisticated security mechanisms, and mandates their implementation by all conforming clients. • NFS Version 4 standardizes the use and interpretation of ACLs across Posix and Windows environments. • NFS Version 4 combines the disparate NFS protocols (stat, NLM, mount, ACL, • and NFS) • NFS Version 4 introduces protocol support for file migration and replication. • NFS Version 4 requires support of RPC over streaming network transport • protocols such as TCP. • For more information on the NFS Version 4 protocol, read RFC 3530. Published under Term of GPL

9. NFS (Network File System) • NFS developed by Sun Microsystems • Native method for file sharing between Unix/Linux systems • Stateless protocol(2&3): • Means server keeps no state: • Renders server crashes `easily recoverable‘ • Should be compatible with all Unix like systems • Best in trusted environment, not highly secure • Best where all user/group IDs are same Often used with Information Services (NIS) to synchronise user/group IDs Published under Term of GPL

10. NFS (Network File System) • Systems are clients, servers or both • Clients import shared filesystems • Servers export shared filesystems • Servers easy to implement via network daemons • Clients require kernel modifications • Linux systems normally work as both already • NFS is NOT Unix/Linux specific (e.g. PCNFS) Published under Term of GPL

11. Exporting File Systems • Exporting handled by daemons .nfsd and Must be running for NFS export to work • Exported file systems listed in /etc/exports, format is: • hostname(flags) [hostname(flags)] • Example: • /tmp *.blah.co.uk(ro) • Exports /tmp to all systems belonging to domain read only J1 • Important flags: • (read only) • (read/write) Published under Term of GPL

12. Exporting File Systems • _squash (map all uid/gid to something) • (specify user ID to map to) • (specify group ID to map to) After changing /etc/exports, restart NFS • killall -HUP rpc.nfsd • killall -HUP mount • or • /etc/rc.d/init.d/nfs restart Published under Term of GPL

13. Viewing exports • ● Use showmount: • $ showmount -e • $ showmount -e hostname • Export list for • landlord.gbdirect.co.uk: • /usr/local/gbdirect/cvsroot • roti.gbdirect.co.uk • /home/adamg • roti.gbdirect.co.uk • /home/andylong Published under Term of GPL

14. Exporting File Systems • along2.gbdirect.co.uk • /home/mikeb • kebab.gbdirect.co.uk • /mnt/cdrom <anon • clnt> • ● uses a to handle requests • ● This must be running (and you must have access to it) to use • ● Check that hosts.allow contains an entry to permit you access, e.g. • ● : ALL or • ● : my.ip.network. Published under Term of GPL

15. Importing File Systems • Mount a remotely exported directory Usually have to be superuser: • $ mount • hostname:/sharename /local/directory • If successful, the export named /sharename on host hostname is mounted on • our mountpoint /local/directory Files accessed just as if local Remote host must be exporting the directory • You must have access permission • Your local mountpoint must exist • Exactly like mounting a device Published under Term of GPL