NFS for Beginners

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What is "NFS"?

NFS stands for "Network File System". It is used to mount a filesystem on a remote machine to let it look like a local directory. A popular "successor" is "iSCSI" (it is just a successor in the meaning of "mounting a filesystem as if it is local").

One can distinguish between kernel based NFS and userland NFS.

Although userland NFS could be as good as kernel based NFS (maybe except of some percentages of performance), there is currently NO full-blown NFS implementation for userland (at least I know none). Some have the drawback to not support files bigger than 4GB, others do not support some other options, etc..

For kernel based NFS you need a kernel with NFS build into the kernel (either fixed or as a loadable module). You can NOT run kernel based NFS with a kernel, which was not enabled for NFS during compilation time.

If you have a kernel with NFS build into, you are NOT ready to go. You also need some userland executables for a working setup.

This userland executables are called the "nfs-utils" paket and consist of a bunch of applications (one time called) and daemons (background tasks). In addition to this paket you also need a startup script which starts the daemons with respect to the right order.

Last but not least, you have to do some configuration to allow access to the local filesystem via NFS.

What belongs to "nfs-utils" and what is it used for?

portmap

This executable is not really part of the "nfs-utils", but essential to get anything working.

NFS uses a method called "RPC" (Remot Procedure Call) to communicate between machines. The portmap executable is a kind of broker which provides the port numbers of specific services if called via RPC remotely.

Without a running portmap, NFS will NOT work.

nfsd

Not yet written.

mountd

Not yet written.

statd

Not yet written.

exportfs

Not yet written.

showmount

Not yet written.

What belongs to the configuration and what is it used for?

/etc/exports

Not yet written.

/etc/hosts.deny

Not yet written.

/etc/hosts.allow

Not yet written.

Example configurations

One directory for one machine

Not yet written.

One directory for three machines

Not yet written.

One directory for all machines in a specific subnet

Not yet written.

Fully open to everyone (no security at all)

Not yet written.