Re: [Sheflug] rlogin

[Al Hudson <nospam [at] york.ac.uk>]

On Mon, 29 May 2000, Ian Wright wrote:

> You're a star. It was the Telnet from both ends at once thing which sorted
> me out. I hadn't realised that working from one end wouldn't provide a
> bidirectional link.

I'm glad you've got it sorted!! 

> The only thing now which puzzles me is that, as I shut
> one machine down completely before exiting the telnet link at the other
> machine and this locked the terminal window on that machine - wouldn't let
> me close that window until I closed down the machine - how does a dumb
> server deal with such things.

Um, off the top of my head I think that's how telnet works, although I may
be wrong (someone more knowledgeable may want to correct me!). I believe
telnet works on a 'piecemeal' basis - that is, the connection made isn't
consistently alive, it sends packets as and when needed. There isn't any
other clever communication between the computers. This means, when the
computer that you were telnetted to went down, the other one has no way of
knowing. You can always kill the session with a 'kill', or 'kill -9' if
it's really bad - just do a 'ps aux | grep telnet' to find the telnet
process, and kill it. OTOH, telnet should realise that the other machine
has gone down, but it probably takes a while :(

> run from other machines on a network. If, as I thought was often the case,
> this server has no keyboard and screen, how can you provide the 'telnet?'
> link to the machine wanting to run a program on the server? I guess there
> must be a more clever way of running the programs than just Telnet and I'm
> still too ignorant to have found it.

It's not completely obvious!! Generally, the easiest way is to use telnet,
rlogin, shh or some other variant. Remember, if you setup your .rhosts
then you can rlogin from one to the other without the need for passwords,
so it's not amazingly difficult. You can write a script to do the job
also, if you're clever about it. But, and this is a key point, remember
with X client & server are swapped around: the server is the graphical
machine which you are on, and the client is the program running on the
remote computer (the server!!). Hope this makes sense!

> Or is there a way to run a script or
> something which will watch for other machines logging onto the network and
> automatically make a connection to them?

There probably is, but off the top of my head I can't think of a clean way
of doing it! Maybe someone else has some ideas. I can think of ways of
running remote X apps in a nicer fashion (i.e, no telnet etc.), but it
involves programming rather than scripting and is decidedly non-trivial. I
could knock up a nasty version in about a week, but I would have thought
someone else would have written something like that already.. anyone else
know of anything that'll do the job?

> > What's not succeeding? It's probably that you don't have one of the
> > packages that it depends on.
> >
> It said I didn't have 'gc' and 'cc' installed - I installed the RPMS for gcc
> and the ./configure found then but then, after some thought, said that I
> still didn't have a working 'C' compiler.

You probably need to install a fuller development environment. There'll be
something missing that you need - usually, the best way is to go into yast
(or whatever) and click on all the development packages. It could be that
you're missing some includes, libraries, linkers, or some other such
necessary part ;)

Cheers,

Alex.

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