Ed Greshko wrote:

On 06/26/2012 09:54 PM, Ken Smith wrote:


{snip} user accessible then
installing a service should enable and start it.


{snip}

Well, IMO, server software should default to disabled. It is not unusual for users
(novices and even experienced) to install server side software they aren't going to
use...at least initially. To have them default to start seems a good choice. This
is especially true when you probably should alter any default configurations.




{snip}
I could argue this both ways. For something like xrdp I think it should
install, enable and run. I can see an argument for other daemons that
need more application specific config that install and default to
disabled might be a good initial position.

{snip}



I've not used XDMCP in years. I think part of the reason I moved away from it is
that when I do "remote" it can be *remote* and the performance over low bandwidth or
high latency links was lacking.



Agree, but over a 1G LAN with modern hardware it should just fly along.

:-) Ken

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On 06/26/2012 04:19 PM, Robert Myers
wrote:


On Mon, Jun 25, 2012 at 5:27 PM, Ken Smith <kens@kensnet.org>
wrote:



Hi, I in danger of making this a rant, but is XDMCP no longer
something that Fedora supports?



gives?





<snip>*



Thanks for any hints and guidance.





I have more than a hint and guidance. *I have emphatic
advice. *Stop trying to import and export desktops, no matter
the system. *Import and export windows or create virtual
machines, but do not ever under any circumstances attempt to
deal with virtual desktops, no matter the Windows or Linux
distribution. *If you get it right once for some circumstance,
whatever you have gotten right will soon become wrong in some
intolerable way just as soon as some weenie somewhere has a
better idea. *No one is more or less a sinner. *All are. *I
know what a virtual machine is and I know what a window is and
so do most systems. *No one seems to be able to agree on what
a desktop is or what its powers are, and that problem is
absolutely fundamental.



Robert Myers




WOW!.....strong words! But sound advice nontheless! I've never
really dealt with the virtual desktops and I seriously doubt I ever
will, I'm not that heavily into having different OS'es or programs
running. I imagine it's helpful to people who actually NEED to have
that kind of setup, but for myself it would just be a frivolous
waste of time to even get involved in it!



EGO II



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Eddie G.O'Connor Jr-I wrote:




On 06/26/2012 04:19 PM, Robert Myers
wrote:


{snip}




I have more than a hint and guidance. *I have emphatic advice.
*Stop trying to import and export desktops, no matter the system.
*Import and export windows or create virtual machines, but do not ever
under any circumstances attempt to deal with virtual desktops, no
matter the Windows or Linux distribution. *If you get it right once for
some circumstance, whatever you have gotten right will soon become
wrong in some intolerable way just as soon as some weenie somewhere has
a better idea. *No one is more or less a sinner. *All are. *I know what
a virtual machine is and I know what a window is and so do most
systems. *No one seems to be able to agree on what a desktop is or what
its powers are, and that problem is absolutely fundamental.



Robert Myers




WOW!.....strong words! But sound advice nontheless! I've never really
dealt with the virtual desktops and I seriously doubt I ever will, I'm
not that heavily into having different OS'es or programs running. I
imagine it's helpful to people who actually NEED to have that kind of
setup, but for myself it would just be a frivolous waste of time to
even get involved in it!



EGO II




I understand what Robert is meaning especially exporting apps rather
than whole desktops.



But I was attempting to get some hands on experience of F17 via a
Virtual Machine installation. The VNC based window from the VM is only
1024x768 whereas my desktop is 2560x1024 and I'd like to get a full
screen or near full screen display.



xrdp and TigerVNC would give the resolution but they only work in Gnome
fallback mode.



I still don't understand why deprecating XDMCP furthers the Open Source
cause. Like many, I'm pretty tenacious and I'll hack my way round the
"enhancements" to get the installation to do what I want it to. But why
should I have to resort to that....



Maybe I should take this up on a Gnome list.





Ken








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On Fri, Jun 29, 2012 at 8:57 AM, Ken Smith <kens@kensnet.org> wrote:









I understand what Robert is meaning especially exporting apps rather
than whole desktops.



But I was attempting to get some hands on experience of F17 via a
Virtual Machine installation. The VNC based window from the VM is only
1024x768 whereas my desktop is 2560x1024 and I'd like to get a full
screen or near full screen display.



xrdp and TigerVNC would give the resolution but they only work in Gnome
fallback mode.



I still don't understand why deprecating XDMCP furthers the Open Source
cause. Like many, I'm pretty tenacious and I'll hack my way round the
"enhancements" to get the installation to do what I want it to. But why
should I have to resort to that....



Maybe I should take this up on a Gnome list.


xdmcp has always been regarded as a security risk.
The problem with screen sizes is part of that "absolutely fundamental" issue that I mentioned. *A desktop thinks (or usually thinks) it has control as to what appearance, like screen size, is presented to the user, or at least it should know what it is and be able to arrange things so that the user sees a usable desktop. *In my experience, the remote desktop is almost always both clueless and powerless, and it will be only *by chance that you can see and use everything that you need to see and use. *Even Windows rdp breaks itself periodically, even though it is glorious when it is working. *Windows fiddled with services for Unix, but clearly realized that, in the hands of a power user, SFU reduces Windows to a mere display manager. *You can now set up an x-server and an ssh daemon under Cygwin, and both Cygwin and processors/graphics cards have become mature enough that it is all usable. **Then* Windows becomes a mere display manager with a working flash, and away you go, even if you have to use Chrome under Windows to display some media.

Robert Myers

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On 06/29/2012 05:57 AM, Ken Smith wrote:


I still don't understand why deprecating XDMCP furthers the Open Source
cause.


Guys, slow down. There's no reason to believe that XCMCP has been
deprecated. It can be enabled exactly as it was in the previous
release. It looks like there's a bug that hasn't yet been reported. It
would be helpful if anyone else could verify that the X server prints an
error to the system's console (not to the logs, not to the controlling
tty, and not to stderr) when they attach it to a Fedora 17 XDMCP server.


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Gordon Messmer wrote:

On 06/29/2012 05:57 AM, Ken Smith wrote:


I still don't understand why deprecating XDMCP furthers the Open Source
cause.


Guys, slow down. There's no reason to believe that XCMCP has been
deprecated. It can be enabled exactly as it was in the previous
release. It looks like there's a bug that hasn't yet been reported.
It would be helpful if anyone else could verify that the X server
prints an error to the system's console (not to the logs, not to the
controlling tty, and not to stderr) when they attach it to a Fedora 17
XDMCP server.



Apologies Gordon, you asked this earlier and I didn't reply.

I would suggest deprecated as the settings for the function have been
buried. It suppose it depends on how you define deprecated.


I note the other comments about security of XDMCP. In this situation
both the office LAN and the internal VLan inside my host are pretty
safe. If I was concerned I would use a VPN or such like. (Folks still
use ftp and telnet.)


The environment I'm testing in is FC13 x64 on an i7 with nVidia graphics
and that is the KVM host for the FC17 VM. The plan is to move the host
up to FC17 if this testing works out OK.


The FC17 VM has this in the /etc/gdm/custom.conf file

[security]
DisallowTCP=0
[xdmcp]
Enable=1

Ports 177 udp and 6000/6001 tcp are open on it.

There are also Centos 5 and 6 {and other} VM's on that host.

"X -query {ipaddr} :1" and "Xnest :1 -query {ipaddr}" work fine between
the Centos5 and 6 VM's and the host in any combination you choose to try.


If I try the access the FC17 VM with "X -query ..." from the FC13 host
or the C6 VM, the machine switches desktop as expected and then displays
the circular mouse icon on a black screen and then the desktop freezes.
Cntl-Alt F1 or 2 etc then do nothing.


Logging on to the "frozen" C6 VM host with ssh shows that the machine is
still up, just its display system is hanging in bits. There is one TCP
session open on port 6001. Trying the kill the "X -query" process fails.
Switching it to RL1 does not restore any desktop. In this case I killed
the virtual power to it, as all the other buttons and switches were
ineffective.


Sadly in this scenario any messages that were shown on the console are
not visible. Nor are they visible if I do this from the host.


Leaving the FC17 host running and then connecting again, this time with
"X -query" or Xnest from the host gives varying results. Soon after the
failed attempt with "X -query ..." I got this error


(EE) open /dev/fb0: No such device
error setting MTRR (base = 0xf0000000, size = 0x00100000, type = 1)
Invalid argument (22)

Fatal server error:
XDMCP fatal error: Session declined Maximum number of open sessions from
your host reached


I got a similar message when I tried with Xnest.

A short time later I tried again with Xnest and got a full logon screen.
I was so surprised I thought I had connected to the wrong host. Trying
again straight away gave this error.


X Error of failed request: BadMatch (invalid parameter attributes)
Major opcode of failed request: 73 (X_GetImage)
Serial number of failed request: 2995
Current serial number in output stream: 2995


You may be on the right track that this may be a bug. If there is any
other info I can provide, such as exact software versions etc please let
me know.


Thanks

Ken






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On 07/02/2012 07:08 AM, Ken Smith wrote:


I would suggest deprecated as the settings for the function have been
buried. It suppose it depends on how you define deprecated.


No, they haven't. They're still in custom.conf, where they've been for
some time. The buried settings discussed earlier apply to GDM, which
has not itself been deprecated.



If I try the access the FC17 VM with "X -query ..." from the FC13 host
or the C6 VM, the machine switches desktop as expected and then displays
the circular mouse icon on a black screen and then the desktop freezes.
Cntl-Alt F1 or 2 etc then do nothing.


It sounds like the X server is crashing or locking up. Try this: Reset
the machine running the X server. Possibly reset the F17 host as well,
since it's complaining about too many sessions from your X server host.
When you run X -query, capture data using strace:


strace -f -s 256 X -query ... > /var/tmp/xtrace.txt 2>&1

After the X server locks, cancel the trace with Ctrl+C. Don't send the
file to the list, because it'll be large. I don't think it has any
sensitive data in it, so maybe compress it and post it somewhere it can
be retrieved (http://ge.tt ?) or send it to me. What we're looking for
is output from glibc similar to what I included previously. It'll be on
lines near the end which indicate calls to writev().

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Gordon Messmer wrote:

{snip}




It sounds like the X server is crashing or locking up. Try this:
Reset the machine running the X server. Possibly reset the F17 host
as well, since it's complaining about too many sessions from your X
server host. When you run X -query, capture data using strace:


strace -f -s 256 X -query ... > /var/tmp/xtrace.txt 2>&1

After the X server locks, cancel the trace with Ctrl+C. Don't send
the file to the list, because it'll be large. I don't think it has
any sensitive data in it, so maybe compress it and post it somewhere
it can be retrieved (http://ge.tt ?) or send it to me. What we're
looking for is output from glibc similar to what I included
previously. It'll be on lines near the end which indicate calls to
writev().
I have the trace you need. Its a busy day today but I'll post again as
soon as I have uploaded it somewhere.


Thanks

Ken

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Gordon Messmer wrote:

On 07/02/2012 07:08 AM, Ken Smith wrote:


I would suggest deprecated as the settings for the function have been
buried. It suppose it depends on how you define deprecated.


No, they haven't. They're still in custom.conf, where they've been
for some time. The buried settings discussed earlier apply to GDM,
which has not itself been deprecated.



If I try the access the FC17 VM with "X -query ..." from the FC13 host
or the C6 VM, the machine switches desktop as expected and then
displays

the circular mouse icon on a black screen and then the desktop freezes.
Cntl-Alt F1 or 2 etc then do nothing.


It sounds like the X server is crashing or locking up. Try this:
Reset the machine running the X server. Possibly reset the F17 host
as well, since it's complaining about too many sessions from your X
server host. When you run X -query, capture data using strace:


strace -f -s 256 X -query ... > /var/tmp/xtrace.txt 2>&1

After the X server locks, cancel the trace with Ctrl+C. Don't send
the file to the list, because it'll be large. I don't think it has
any sensitive data in it, so maybe compress it and post it somewhere
it can be retrieved (http://ge.tt ?) or send it to me. What we're
looking for is output from glibc similar to what I included
previously. It'll be on lines near the end which indicate calls to
writev().


I have just sent the below to Gordon off list with an attached file with
the traces.


Hi Gordon,

I attach a tar.gz file with the traces. It only 500k so e-mail should cope.

These were done with the FC13 machine, that acts as the VM host, as an X
server and the FC17 VM acting as an X client. The FC17 was freshly
booted. I had a ssh session logged in to the FC13 from another machine
as I was expecting to lose control of the desktop of the FC13 machine
during these tests.


The file xtrace.txt is a trace using Xnest from a normal user account on
the FC13 X server.


The file xtrace2.txt is a trace of a repeat of the last Xnest command
but this time a login desktop appeared and allowed me to start entering
logon details before it vanished off the screen


The file xtrace3.txt is a trace of a "X -query ..." command from a
normal user account on the FC13 X server


The file xtrace4.txt is a trace of a "X -query ..." command from the
root account on the FC13 X server. As previously the desktop switched to
the new X display and it showed a small round icon that was movable with
the mouse.


The file xtrace4-copy.txt is a copy of xtrace4.txt made after running
the "X -query ..." command but before rebooting that machine to regain
control of the desktop.


There's some interesting things in that xtrace4.txt file about malloc
and memory corruption.


Hope this helps

Ken


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