"sudo gvim" is ok on a non-root shell.
$ sudo gvim /etc/fstab
[sudo] password for ts:

However, "E233: cannot open display" error appears when starting gvim
on ubuntu 8.04 root shell.
# gvim /etc/fstab
E233: cannot open display
Press ENTER or type command to continue
# kdesudo gvim /etc/fstab
kdesudo: cannot connect to X server

TsanChung <tsanchung.w... at (no spam) gmail.com> wrote:
"sudo gvim" is ok on a non-root shell.
$ sudo gvim /etc/fstab
[sudo] password for ts:

However, "E233: cannot open display" error appears when starting gvim
on ubuntu 8.04 root shell.
# gvim /etc/fstab
E233: cannot open display
Press ENTER or type command to continue
# kdesudo gvim /etc/fstab
kdesudo: cannot connect to X server

That's now X works.
To use X from another user, such as root, the DISPLAY environment variable
must be set and the X server TOLD to allow it.

Try this...
xhost + localhost
sudo DISPLAY=localhost:0.0
sudo gvim

"sudo gvim" is ok on a non-root shell.
$ sudo gvim /etc/fstab
[sudo] password for ts:

However, "E233: cannot open display" error appears when starting gvim
on ubuntu 8.04 root shell.
# gvim /etc/fstab
E233: cannot open display
Press ENTER or type command to continue
# kdesudo gvim /etc/fstab
kdesudo: cannot connect to X server

TsanChung <tsanchung.w... at (no spam) gmail.com> wrote:
"sudo gvim" is ok on a non-root shell.
$ sudo gvim /etc/fstab
[sudo] password for ts:

However, "E233:cannotopendisplay" error appears when starting gvim
on ubuntu 8.04 root shell.
# gvim /etc/fstab
E233:cannotopendisplay
Press ENTER or type command to continue
# kdesudo gvim /etc/fstab
kdesudo:cannotconnect to X server

That's now X works.
To use X from another user, such as root, theDISPLAYenvironment variable
must be set and the X server TOLD to allow it.

Try this...
xhost + localhost
sudoDISPLAY=localhost:0.0
sudo gvim

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On the root shell of Konsole on ubuntu 8.04.
# DISPLAY=localhost:0.0
# xclock
Error: Can't open display: localhost:0.0
# gvim /etc/fstab
E233: cannot open display
Press ENTER or type command to continue
# kdesudo gvim /etc/fstab
kdesudo: cannot connect to X server

# xhost + localhost
xhost: unable to open display "localhost:0.0"

# DISPLAY=:0.0
# xclock
Invalid MIT-MAGIC-COOKIE-1 keyError: Can't open display: :0.0
# DISPLAY=:0
# xclock
Invalid MIT-MAGIC-COOKIE-1 keyError: Can't open display: :0

TsanChung wrote:
On the root shell of Konsole on ubuntu 8.04.
#DISPLAY=localhost:0.0
# xclock
Error: Can'topendisplay: localhost:0.0
# gvim /etc/fstab
E233:cannotopendisplay
Press ENTER or type command to continue
# kdesudo gvim /etc/fstab
kdesudo:cannotconnect to X server

# xhost + localhost
xhost:  unable toopendisplay"localhost:0.0"

#DISPLAY=:0.0
# xclock
Invalid MIT-MAGIC-COOKIE-1 keyError: Can'topendisplay: :0.0
#DISPLAY=:0
# xclock
Invalid MIT-MAGIC-COOKIE-1 keyError: Can'topendisplay: :0

You'll get that error if /etc/hosts defines only 127.0.0.1 as localhost,
but you're connected over IPv6.  Edit /etc/hosts so that BOTH 127.0.0.1
and ::1 are defined as localhost.

Since you're apparently connected via ssh, you really shouldn't have to
mess with xhost.  In fact, messing with xhost is usually very bad for
security.  Just connect with the -X switch, which you're probably
already doing.

On Oct 7, 7:51 pm, Allen Kistler <ackist... at (no spam) oohay.moc> wrote:
TsanChung wrote:
On the root shell of Konsole on ubuntu 8.04.
#DISPLAY=localhost:0.0
# xclock
Error: Can'topendisplay: localhost:0.0

[snip]


[snip]


I followed your instructions to edit /etc/hosts as follows but the
problem still exists.
127.0.0.1 localhost
::1 localhost
127.0.1.1 tc-desktop

# The following lines are desirable for IPv6 capable hosts
#::1 ip6-localhost ip6-loopback
...

I am using gvim on the root shell of Konsole on ubuntu 8.04, I am not
using ssh. I experiment with xhost because I want to solve the
"cannot open display" problem.

TsanChung wrote:
On Oct 7, 7:51 pm, Allen Kistler <ackist... at (no spam) oohay.moc> wrote:
TsanChung wrote:
On the root shell of Konsole on ubuntu 8.04.
#DISPLAY=localhost:0.0
# xclock
Error: Can'topendisplay: localhost:0.0

[snip]

[snip]

I followed your instructions to edit /etc/hosts as follows but the
problem still exists.
127.0.0.1       localhost
::1             localhost
127.0.1.1       tc-desktop

# The following lines are desirable for IPv6 capable hosts
#::1     ip6-localhost ip6-loopback
...

I am using gvim on the root shell of Konsole on ubuntu 8.04,  I am not
using ssh.  I experiment with xhost because I want to solve the
"cannotopendisplay" problem.

Sorry.  I missed your mention of Konsole the first time.  I got
distracted byDISPLAY=localhost:0.0.

So now I'm wondering why you setDISPLAY.  It should have already been
:0.0 (i.e., no localhost hostname), which is the correct value for
someone at the console.

If you justopena terminal window and "echo $DISPLAY" then what do you
get?  If you don't setDISPLAYfirst, does xclock or gvim give an error
then?  They should just work without changingDISPLAY.