tftpd and paths...

John F. Kohler jkohler2 at earthlink.net
Tue Sep 7 18:27:35 PDT 1999


Mike,
Your explanation below clears up a lot for me.  I am sure, as I continue
to learn more about the Linux kernal and its operating system, I will
become more familiar with the computer and its associated software. 
Right now, I am primarily an "appliance user."
Thanks again for the detailed account.  I will re-read it again a couple
of times and maybe print it.

john 

Mike wrote:
> 
> On Tue, 7 Sep 1999, John F. Kohler wrote:
> > Subject: Re: tftpd and paths...
> >
> > and...I don't understand the answer.
> >
> > ...lots to learn..
> > John
> General overview on where and why it may be used (tftp)
> 
> tftp : trivial file transfer protocol
> tftpd: trivial file transfer protocol daemon
> (The daemon is the server, the one without the daemon as part of its name
> is the client)
> 
> tftp is a protol that can be used by any machine on the network to request
> a file from a tftp server *without* authentication.
> 
> Normally, if you used standard ftp to get a file from an ftp server, you
> would:
> $ ftp hostname.here.com
> Name (hostname.here.com:user): anonymous
> 331 Guest login ok, send your complete e-mail address as password.
> Password: (not shown here, or echoed back with false characters)
> 
> >From here I can cruise through their directories and "GET" files for
> myself.
> 
> tftp is different.
> 
> tftp does not require this step for authentication. tftp make a requst of
> the server, like:
> Give me the file located at /kernels/linux-2.0.36
> (to which the server look sto see if that file exists in its tftpd served
> directory like: /tftpboot or /boot for the full path of:
> /tftpbootp/kernels/linux-2.0.36 or /boot/kernels/linux-2.0.36 )
> (The tftp daemon considers its starting directory the root directory so
> any request it gets has a "/tftpboot" or "/boot" prepended to it.)
> 
> The tftpd server then sends the file (if it has the file and it is
> publicly readable) to the client.
> 
> You do not often run into tftp/tftpd any more. The most common use it has
> if for updating BIOS, or firmware on specialized network equipment, or in
> this case to help a diskless workstation get started.
> 
> Diskless workstations often use an ethernet card with an EPROM programmed
> with information on how to get an IP address with something called BOOTP
> or DHCP.
> (BOOTP: Boot Parameters Server)
> (DHCP : Dynamic Hosts Configuration Protocol)
> 
> When the machine is first started, it goes through a POST (power On Self
> Test) and examines its internal BIOS (Basic Input Output System) for
> devices that will allow it to boot an OS (Operating system.) Common
> devices in many machines include:
> Floppy disk
> Hard Drive
> CD-ROM (sometimes in newer machines)
> A special EPROM chip added to an ethernet card, or certain types of
> hardware designed to be network booted, or use of a specially created
> floppy can allow you to make some machines "boot" their operating system
> and grab their file systems from over the network.
> (EPROM Erasable Programmable Read Only Memory)
> 
> So here is what can happen in a network booted system:
> You turn on the machine.
> The machine looks through the list of hardware from which is may boot.
> The machine finds the ethernet card.
> The machine reads the BIOS from the ethernet card and understands how to
> send out a bootp request, understand the response, and memorize it.
> Part of the BOOTP (or DHCP) response includes an IP address, AND what
> server it is told will be a tftpd server, as well as what root directory
> it should find a file from the tftpd server and what file it will need.
> The machine sets its IP address up, and then uses its IP address to send
> out a tftp request (using the TCP/IP protocol suite since now it has an
> IP address) to the tftpd server it was told inthe BOOTP (or DHCP)
> response to get the file from...
> The tftpd server sends the file (if it has it, and it is publicly
> readable).
> The machines gets the file reads it into memory and continutes booting
> from it... (more steps are needed like NFS etc, but wiull not be covered
> here...) (NFS: Network File System)
> 
> for more information, from a unix shell see:
> man bootp
> man dhcp
> man tftp
> man tftpf
> man bootptab
> Install the "netboot" package (if you have it available) and
> man mknbi-dos
> man mknbi-linux
> 
> and do some searches at Linux.org in the HOW-TO and Mini-How-to sections
> for network booting for more complete descriptions...
> 
> Andru and I first did some work with tftp a few years ago when we
> net-booted some Sun 3/50 and Sun 3/60 machines over a network. Now we have
> about 16 Linux based diskless workstations in use at work. They are GREAT
> for us. They have little maintenance. Everything is stored on the server,
> and executed on the diskless workstations. There are only 2 moving parts:
> The fan on the CPU and the fan on the power supply. If any one of them has
> a failure, then they are just "reset" and the machine reboots over the
> network.
> Andru is mostly responsible for setting this up and pushing it through at
> our work. He is the one that first suggested the idea, and made this
> happen.
> 
> -M
> P.S. Ignore the typos, I do.



More information about the talk mailing list