xterm -C switch doesn't work under Fedora

[Olin Shivers]

xterm has a -C option that causes it to run as a "console" --
that is, the xterm displays messages sent to the console. This
is a handy thing -- I usually run a small console xterm in one
corner of my laptop's screen, so that I can see things that are
going on in my system.

Unfortunately, this functionality seems to be broken under Fedora.
Now, when this feature *usually* breaks, it's *usually* due to
/dev/console permission problems. But not this time -- gdm properly
gives me ownership of /dev/console when I log in:

% ls -l /dev/console
crw------- 1 shivers root 5, 1 2007-12-11 15:31 /dev/console
%

Nonetheless, when I run xterm -C I get an error message:

% xterm -C
xterm: cannot open console: Operation not permitted

and the xterm doesn't display any console messages. Furthermore, when
I search for operations on /dev/console with strace I get these:

% strace xterm -C 2>&1 | fgrep dev/console
stat64("/dev/console", {st_mode=S_IFCHR|0600, st_rdev=makedev(5, 1), ...}) = 0
access("/dev/console", R_OK|W_OK) = 0
%

What's weird is that, according to strace, the access() call is *winning* --
zero return means access is permitted.

One more odd sympton: if I run xterm -C as root, then
- I *don't* get the "cannot open console" error message (which is good);
- strace says the stat64() call happens, but the access() call isn't even made (which is odd);
- the xterm does *not* display console messages (which is bad).

Here's an example:
# strace xterm -C 2>&1 | fgrep console
stat64("/dev/console", {st_mode=S_IFCHR|0600, st_rdev=makedev(5, 1), ...}) = 0
#

I also observe, by the way, that the venerable xconsole program has similar
kinds of lossage. Xconsole is nice because it's not interactive -- it's
display-only. This is nice, because I hack my gdm scripts so that the
login panel puts an xconsole in the lower right corner of the screen. That
way, you can see what's happening on the machine, even if you aren't logged
in and can't run any commands. But under Fedora, this doesn't work and I
can't figure out why.

Does anyone have any suggestions? Should I file a bug report to Fedora?

I realise that this kind of UI is pretty old-school -- most people get their
notifications one painful, intrusive pop-up at a time via a notification
applet in a gnome panel, instead of simply having them neatly stream by on
a console. Call me traditional. It's a documented feature in these apps; it
should work.

-Olin

[FriedChips]

Originally Posted by Olin Shivers

Should I file a bug report to Fedora?

That would be my only suggestion for you.. Let the dev's know so then it will work for everyone.

[leadgolem]

Hmm, very interesting.

xterm -C
xterm: cannot open console: Operation not permitted
[leadgolem@localhost ~]$ su
Password: 
[root@localhost leadgolem]# xterm -C
Warning: Tried to connect to session manager, Authentication Rejected, reason : None of the authentication protocols specified are supported and host-based authentication failed

[stevea]

It works perfectly when you stop the console-kit

service ConsoleKit stop

If you probed a little harder (try "strace -f") You'd see that xterm creates child process and this child attempts and fails with the system call setpgid(0,0) and also a close (which I doubt its the problem). The child correctly reports the "not permitted" message.

lsof /dev/console
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
gdm-binar 2341 root 6w CHR 5,1 211 /dev/console
gnome-key 2387 stevea 6w CHR 5,1 211 /dev/console
console-k 6571 root 9r CHR 5,1 211 /dev/console

So console-kit process is already reading /dev/console. Doing so again would make a mess. And yo ucan't change the pgid of console-kit from root. You may disagree with the "xterm -C" or console-kit design, but it isn't an error.

No problem here - move along.

[kadambi]

Doesn't work for me either. I see the same behavior.