VectorLinux

Please login or register.

Login with username, password and session length
Advanced search  

News:

Visit our home page for VL info. For support and documentation, visit the Vector Linux Knowledge Center or search the Knowledge Center and this Forum using the search box above.

Author Topic: X display woes  (Read 1307 times)

linuxsurd

  • Member
  • *
  • Posts: 3
X display woes
« on: January 04, 2008, 06:15:09 am »

I'm running VL5.8 (2.6.18.5). I've had minor bumps along the way with one I have not figured out.

When I use telnet (via /usr/X11R6/bin/xterm, Command Prompt X terminal emulator or putty) I get

env shows:
HOSTNAME=vector.linux.net
HOST=vector.linux.net
SESSION_MANAGER=local/vector.linux.net:/tmp/.ICE-unix/9995
DISPLAY=:0.0

I do the following:
[vector] ~ > xhost +
access control disabled, clients can connect from any host
[vector] ~ > xclock
[vector] ~ > telnet xxx.yyy.zzz.com
Trying 172.18.35.8...
Connected to xxx.yyy.zzz.com
Escape character is '^]'.
....
...
> echo $DISPLAY
vector.linux.net:0.0
> xclock
Error: Can't open display: vector.linux.net:0.0

Then I manually set the display to my IP.

> setenv DISPLAY a.b.c.d:0.0
> xclock
Error: Can't open display: a.b.c.d:0.0

I can successfully ssh to some other remote sun host at my work LAN and export my display and run x applications fine. (on the ssh session I notice the DISPLAY is default set to "localhost:13.0".
I can't understand why ssh is fine but my telnet session fails. I am able to run X-apps with telnet from a WinXP-Xceed session on a laptop.

Can someone explain what's happening here with X and telnet on my VL5.8 box ? Is it something to do with the hostname I chose (vector.linux.net) or my X config on VL or something else ?
« Last Edit: January 04, 2008, 07:02:16 am by linuxsurd »
Logged

Triarius Fidelis

  • Vecteloper
  • Vectorian
  • ****
  • Posts: 2399
  • Domine, exaudi vocem meam
    • my website
Re: X display woes
« Reply #1 on: January 04, 2008, 06:28:18 am »

It has to do with SSH itself. SSH can enable forwarding of X traffic (hence the curious 'localhost:13.0' host name you saw); IIRC, that forwarding functions even behind a firewall or NAT. Telnet does not have that feature. I should point out that 'xhost +' as well as Telnet in general are dangerous to use from a security standpoint.
Logged
"Leatherface, you BITCH! Ho Chi Minh, hah hah hah!"

Formerly known as "Epic Fail Guy" and "Döden" in recent months

linuxsurd

  • Member
  • *
  • Posts: 3
Re: X display woes
« Reply #2 on: January 04, 2008, 07:08:34 am »

Thanks for the reply. I agree about the security issues.

But can you explain why I can run the same telnet session with X using a WinXP/eXceed setup and bring up an X application ? I don't have the ssh daemon running on these remote hosts so I can't use ssh with some hosts. I am within a secure network so I could live briefly with these telnet sessions.
Logged

Triarius Fidelis

  • Vecteloper
  • Vectorian
  • ****
  • Posts: 2399
  • Domine, exaudi vocem meam
    • my website
Re: X display woes
« Reply #3 on: January 04, 2008, 07:13:48 am »

But can you explain why I can run the same telnet session with X using a WinXP/eXceed setup and bring up an X application ? I don't have the ssh daemon running on these remote hosts so I can't use ssh with some hosts. I am within a secure network so I could live briefly with these telnet sessions.

I haven't used eXceed. Does that offer any special means of tunneling?
Logged
"Leatherface, you BITCH! Ho Chi Minh, hah hah hah!"

Formerly known as "Epic Fail Guy" and "Döden" in recent months

linuxsurd

  • Member
  • *
  • Posts: 3
Re: X display woes
« Reply #4 on: January 04, 2008, 08:07:14 am »

There's no tunneling for the telnet session that I configured in eXceed (windows). That seems only for ssh sessions.
Logged