[R] Ryacas not working properly

[Marc Schwartz]

Gabor,

>From what I can tell, telnet service is not actually required to run
yacas.  This is what confused me for some time and what raised the
spectre of the concerns that had I for yacas to be dependent on telnet,
as opposed to say ssh.

On FC6 (and I suspect many other distros), telnet (plus or minus
kerberos support) is not enabled by default, given the known security
issues.

One can, from the:

  System -> Administration -> Server Settings -> Services

menu, select the "On Demand Services" tab and enable telnet there.  This
way, telnet is not running by default, but only when actually needed.

After trying various permutations of settings, suspecting SELinux and/or
firewall issues, I came to the conclusion that enabling this is not
required.

By default, the telnet server listens to port 23, which was another red
flag that I had, noting the error messages for port 9734.  I noted no
problems from iptables (the Linux firewall rules), given that I do not
have port 23 open for telnet service.

When yacas is running, I see no indication that processes related to
telnet are running, which should be the case, given that I have
explicitly disabled telnet as root and SELinux enforces those settings
based upon mandatory policies.

Without digging deeper into the yacas engine, it may very well be that
without the --server-enabled option, it does require a telnet server to
be running as the means to pass the expressions for evaluation. However,
with that option enabled, yacas has its own server and uses port 9734. I
also noted no references to 'telnet' in the config.log, created during
the build process.

However, I could not get yacas working without the server related
option, even with telnet enabled, SELinux in Permissive mode and the
firewall disabled on my system.

This interaction was a great source of confusion, so it would be
worthwhile to query the yacas folks to get some clarification relative
to the presumptive dependency on telnet, which may end up being OS
specific.

HTH,

Marc

On Sun, 2006-11-19 at 19:32 -0500, Gabor Grothendieck wrote:
> I don't have a UNIX box but my reading of it is that it is
> telling one how to enable telnet on the machine -- not
> how to install a server -- and that once telnet is enabled
> then the Ryacas package can make use of sockets
> whereas without that such use of sockets is disabled.
> Is that not right?
> 
> 
> On 11/19/06, Paul Smith <phhs80 at gmail.com> wrote:
> > On 11/19/06, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> > > Thanks, Marc.  I have placed a link to your post on the Ryacas home page.
> > > Also, Ryacas 0.2-3 is now on Omegahat (as well as google groups).
> >
> > Apparently, the link
> >
> > "HowTo - Enable Telnet on Linux"
> >
> > at Ryacas site is misleading, as it suggests the installation of
> > telnet-server and that is not necessary. See the discussion at
> >
> > http://groups-beta.google.com/group/comp.os.linux.networking/browse_thread/thread/2bb6a4c7a1167285/565dde88d7922659#565dde88d7922659
> >
> > Paul

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