Hi,

  Thanks for that. I  had all that set already, it isn't the cause of the problem.
I think the point is that the route back for the forwarded X11 is via a port called localhost:6011,
but if the machine can not work out what localhost is then it fails. You need either one of

127.0.0.1       localhost.localdomain   localhost
or
::1 localhost

in /etc/hosts

  Alex


Fernando M. Roxo da Motta wrote:
> On Wed, Dec 06, 2006 at 04:59:22PM -0600, Troy Dawson wrote:
>> Alex Finch wrote:
>>> I find that X11 forwarding over ssh does not work on SL 4.4. I get the 
>>> message
>>> _X11TransSocketINETConnect() can't get address for localhost:6011: Name 
>>> or service not known
> =================8<-----------------------------
>> The easiest fix I know of is to edit
>>   /etc/ssh/ssh_config
>> and add the line
>>        ForwardX11 yes
>> I usually put it at the end, so that it looks like
>>
>>        ForwardX11Trusted yes
>>        ForwardX11 yes
>>
> 
> 
>   Just as an aditional information, the first option above
> (ForwardX11Trusted) will export the DISPLAY with all, or almost all,
> extensions available.  See the output of xdpyinfo(1) command in local and
> remote hosts to get the available X11 extensions.  Without that option
> only a few extensions are made available in the remote (X11 client)
> machine and many applications fail, due to the lack of resources, with some
> cryptic message that explains nothing.
> 
>   Anyway it is neccessary some care in order to avoid export all resources
> to the world, as it may represent some security threat.    Perhaps a
> solution like :
> 
> =============8<-------  cut here  -----------
> 
> #  Inside my network   -------------------------
> # This one is not trusted at all
> Host noexport.at.mynet
>    ForwardX11 no
> 
> # This one is not all trusted
> Host partial.at.mynet
>    ForwardX11Trusted no
>    ForwardX11 yes
> 
> # I trust all others
> Host *.at.mynet
>    ForwardX11Trusted yes
>    ForwardX11 yes
> 
> #  Outside my network  -------------------------
> 
> # The ones I trust
> Host somehost.at.some.place
>    ForwardX11Trusted yes
>    ForwardX11 yes
> 
> # I trust "ma non troppo"
> Host other.not.so.trusted
>    ForwardX11Trusted no
>    ForwardX11 yes
> 
> #  Global Defaults
> Host *
>    ForwardX11 no
> 
> 
> =============8<-------  cut here  -----------
> 
>   Points to note in config above, from ssh_config(5) :
> 
>      Since the first obtained value for each parameter is used, more host-
>      specific declarations should be given near the beginning of the file,
>      and general defaults at the end.
> ...
>      Host    Restricts the following declarations (up to the next Host 
>              keyword) to be only for those hosts that match one of the
>              patterns given after the keyword.  * and ? can be used as 
>              wildcards in the patterns.  A single * as a pattern can be 
>              used to provide global defaults for all hosts.  The host 
>              is the hostname argument given on the command line (i.e., 
>              the name is not converted to a canonicalized host name before
>              matching).
> 
>   Some of these can (should?) be inside the sitewide '/etc/ssh/ssh_config'
> and those that differs must be in '~/.ssh/config'.   A question to ALL,
> can this config be in a NIS map or some sort of LDAP directory ?
> 
>   An extra information learned from experience.  If the home directory
> and/or the '~/.ssh' have insecure access permissions the personal
> configuration is silently ignored.   So if you change configs and it takes
> no effect, look at those permissions.
> 
> 
>   HTH
> 
> 
>   Roxo
> 


-- 
  Alex Finch, Research Fellow, Physics Department, Lancaster University.
+44 (0) 1524 593618   http://www.lancs.ac.uk/depts/physics/staff/ajf.htm