Introduction

This project can be extended in the future in the way that: if you want to run Linux in the SGI machine, you need this kind of network environment. Then you can export the kernel and utilities compiled for MIPS.

Bootstrap and Trivial File Transfer Protocols

BOOTP

• Server: You can run booptd deamon as a stand alone server or through inetd deamon. In the first case, only type bootpd -s. In second case, modify /etc/inetd.conf & /etc/services files to make sure the corresponding deamon isn't marked. Most important, configure the file,/etc/bootptab, to let the client with hardware address can find its IP address and hostname. There are also several useful utility you can test your bootp server.
  • bootpgw: when the request is through different segments,you can use this program as a gateway to forward the request only.
  • bootptest: you can test the server in the client first to see if the server is configured correctly.
  • bootpef:BOOTP Extension File compiler. You can use to check your syntax in the /etc/bootptab file.
• Client:Get the netboot package (the package is available from your favorite linux mirror site in the /pub/Linux/system/Linux-boot directory or download from here.) In this package, you can compile the boot image for the client, which will contain the bootp and tftp clients. You can either burn the image into your network EPROM or use dd command to write to the floppy. You also need to convert the kernel image to the network bootable image (nbi) using the utility in this package. This package supports Linux and DOS running the client through BOOTP.

TFTP

• Server:Edit the files /etc/services & /etc/inetd.conf.Search tftp string,take the remark off if they are remarked.
• Client:Same as bootp client

Network File System

NFS allows us to share filesystems among computers in an almost transparent manner. NFS was originally implemented as a surrogate filesystem for diskless clients, but has now evolved into a file sharing panacea. NFS consists of several components namely

1. Mounting protocol and server
2. File locking protocol and server
3. Deamons coordinating file services

Basic Operation:
The server "exports" a filesystem when it makes the filesystem available for use by other machines. The client must explicitly mount a filesystem before using it. Upon receiving an initial client mount request, the server checks to see if the client has p roper authorization and if so, sends the client a "magic cookie" which the client uses for subsequent requests. The daemons involved are

1. mountd
   Responds to mount requests. /etc/exports file contains a list of files that the server is exporting to the client along with the permissions. The Client can also modify its /etc/fstab file to mount remote files using NFS
2. nfsd
   Once a client's mount requests have been validated, it is allowed to request various filesystem operations. These requests are executed by nfsd. It is advisable to have multple copies of nfsd running concurrently for improved performance (optimal valu e = 4)
3. rpcbind
   rpcbind is a server that converts RPC program numbers into universal addresses. It must be running on the host to be able to make RPC calls on a server on that machine. When an RPC service is started, it tells rpcbind the address at which it is listening, and the RPC program numbers it is prepared to serve. When a client wishes to make an RPC call to a given program number, it first contacts rpcbind on the server machine to determine the address where RPC requests should be sent.

Diskless Clients:
These machines depend on the NFS server for all filesystem operations.They have no hard drive of their own and mount their entire filesystem through NFS. They are totally dependent on the NFS server for their secondary storage and cannot operate independently. The NFS support is built into the kernel so that they know that they have to mount all their directories including / through NFS. The /etc/fstab file identifies the directories that have to be mounted and their mount points.

Workstation model:
These machines have their own hard drives. They mount directories such as /, /etc, /var etc. from their own hard drives. User directories are usually mounted through NFS so that users can access their files irrespective of the machine into which they log in. /etc/fstab file can be used to mount these directories. Alternately, mount command can be used to manually mount required directories. These workstations can work on their own even in the event of a NFS server crash (of course they would not be of much use!!!!!).

Trouble Shouting

• After Linux is installed( Redhat, Slakware, or others), there will be a bunch of deamons combined with with init program. Check all these deamons (using ps aux) and disable those you don't want it or you don't know why they are running. Otherwise, the request will take lots of time to get the reply without any reasons.
• The kernel for the clients needs to include NFS-root option. Make sure the right bootImage is tftped.
• The file system exported for the clients should be runnable. That means you can not just copy/uncompress the packages. You need to install and setup these packages just like you are installing a new system.
• RedHat doesn't follow the usual Linux boot-up procedure. Thus when exporting the root file system, we stuck at its network setup and kept getting "NFS: notice ..." error message. After changing to Slakware distribution, the scripts are much easier to modified to let the root file system run through NFS server.

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