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Re: Why is DISPLAY variable sometimes simple and others FQDN

 
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Esteemed Contributor

Why is DISPLAY variable sometimes simple and others FQDN

I have 3 HP-UX 11.31 virtual machines - in theory set up identically ('in theory').

On 2 of them when I log in from my PC using Exceed Xterminal emulator, they report the DISPLAY variable as 'fred:31.0', but on the other machine it is reported as 'fred.domain.co.uk:40'?

 

Please note it is the fact that 2 are reporting simple names and the other a FQDN that I am querying, not the 31/40 difference.

 

Note also that /etc/nsswitch.conf, /etc/resolve.conf and /etc/hosts are the same on all 3 machines.

 

What I really want to do is is find out why the 3rd machine is reporting a FQDN and fix it so that it reports a simple name like the other 2 (I don't want to work around this problem by putting code in my .profiles).

 

Many thanks,

 

Gary

5 REPLIES 5
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Honored Contributor

Re: Why is DISPLAY variable sometimes simple and others FQDN

This is likely a PC or Exceed issue. Unless you are setting the display variable in /etc/profile or .profile, the Exceed program is forming the DISPLAY variable. Use nsquery on all 3 machines to verify that from HP-UX, they are the same. Then on the PC, use nslookup for both the IP address and the simple hostname for each HP-UX box. This probably a DNS server issue for the PC.



Bill Hassell, sysadmin
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Honored Contributor

Re: Why is DISPLAY variable sometimes simple and others FQDN

> This is likely a PC or Exceed issue. [...]

   I know nothing, but I'd tend to blame the HP-UX configuration(s)
rather than anything on the Windows side.

> [...] Unless you are setting the display variable in /etc/profile or
> .profile, the Exceed program is forming the DISPLAY variable.

   The DISPLAY variable is a property of the shell on the HP-UX system,
which is not something I'd expect a remote system to be able to fiddle
(in the way that, say, ~/.profile on the HP-UX system might).

   If the connection uses SSH, and X forwarding is enabled, then I'd
expect the SSH server (sshd, on the HP-UX system) to set DISPLAY.  The
funny display numbers (31, 40) suggest (to me) virtual displays
established by an SSH server.

> [...] when I log in from my PC using Exceed Xterminal emulator, [...]

   Log in _how_, exactly?  RSH/remsh?  SSH?  Telnet?


> [...] 'fred:31.0' [...]

   Who is "fred", the Windows system or an HP-UX system?  (If HP-UX, how
many of the virtual machines have the same name?  Or does "fred"
disguise a variety of different names?  (And how helpful was that?))

   I could guess more, but not knowing who's who makes a lucky guess
less likely.

> [...] and /etc/hosts are the same on all 3 machines.

   That would suggest DNS, but everything could depend on who's who.

Highlighted
Esteemed Contributor

Re: Why is DISPLAY variable sometimes simple and others FQDN

Hi Bill,

 

I don't think it's a DNS issue for the PC as the PC doesn't have any name resolution for any of the 3 HP-UX hosts...

 

nsquery of my Windows host returns exactly the same result for all 3 HP-UX machines...

root@devp51:/# nsquery hosts fred

Using "dns [NOTFOUND=continue UNAVAIL=continue TRYAGAIN=continue] files " for the hosts policy.

Searching dns for fred

Hostname: fred.domain.co.uk

Aliases:

Address: 192.168.193.11

Switch configuration: Terminates Search

root@devp51:/#

 

Also, my PC can resolve neither the hostname nor the IP address for any of my HP-UX Machines. So that doesn't explain why they should be different - it must be something to do on HP-UX .

 

 

Highlighted
Esteemed Contributor

Re: Why is DISPLAY variable sometimes simple and others FQDN

Hi Steven,

 

Let me give you a bit more background...

 

'fred' is a Windows 2008 R2 terminal server. It has Open Text Exceed X-Terminal Emulator software installed on it.

 

To connect to one of my HP-UX boxes, I start Exceed in 'XDMCP Broadcast' mode on the Windows machine, fred. This brings up a list of all hosts on my network which can service the request. I then double-click an HP-UX host name on the list and it connects to the host and displays a CDE login screen. I then log in via the CDE login screen using my Unix credentials (root or another user) and it brings up a normal HP-UX windowed session.

 

My HP-UX VMs are called devp51, devp52 and devp53. I can run multiple concurrent Exceed sessions on 'fred' (and so connect to all 3 VMs at the same time with 3 different instances of Exceed) and because fred is the X-server, each session gets a different number, hence 31, 40 etc.

 

I hope that clarifies things a bit.

 

Cheers,

 

Gary

Acclaimed Contributor

Re: Why is DISPLAY variable sometimes simple and others FQDN

A nice page about how XServer works:

 

http://dustwell.com/how-x-over-ssh-really-works.html


Hope this helps!
Regards
Torsten.

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