Do you have selinux-policy-targeted installed?

Yes. That package is installed and running.
[awang@mars t1]$ rpm -q selinux-policy-targeted
selinux-policy-targeted-3.9.16-32.fc15.noarch
[awang@mars t1]$ getenforce
Enforcing
I downloaded the source RPM and it appears it is complaining about the "semanage user -a  -S targeted -P xguest -R xguest_r xguest_u  2> /dev/null  || :(useradd -c "Guest" -Z xguest_u xguest || semanage login -a -S targeted -s xguest
_u xguest || semanage login -m -S targeted -s xguest_u xguest) 2>/dev/null || ex
it 1" portion. At least in my system. 
Thanks.

Created attachment 512714 [details]
Can you execute this shell to see what it is complaining about?

sh /tmp/xguest.sh

I'm seeing this as well:

Cmdline output:

$ semanage user -a -S targeted -P xguest -R xguest_r xguest_u
$ useradd -c "Guest" -Z xguest_u xguest || semanage login -a -S targeted -s xguest_u xguest || semanage login -m -S targeted -s xguest_u xguest || echo "failed"
/usr/sbin/semanage: Linux User xguest does not exist
useradd: warning: the user name xguest to xguest_u SELinux user mapping failed.
/usr/sbin/semanage: Linux User xguest does not exist
/usr/sbin/semanage: Login mapping for xguest is not defined
failed
$

Here is the output.
[root@mars ~]# cd /tmp
[root@mars tmp]# chmod a+x xguest.sh 
[root@mars tmp]# ./xguest.sh 
+ semanage user -a -S targeted -P xguest -R xguest_r xguest_u
+ echo xguest:exclusive
+ semanage -S targeted -i -

BTW, I rebuild the package with the downloaded script and it can be installed. I will try to log out my current session and give it a spin later today.

Sorry, I was wrong about what I said before. I guess the reason I didn't run into problem was because I tried on the machine I messed around already. Here is what I got from a "clean" machine.
[root@arnoldw tmp]# ./xguest.sh 
+ semanage user -a -S targeted -P xguest -R xguest_r xguest_u
+ useradd -c Guest -Z xguest_u xguest
useradd: warning: the home directory already exists.
Not copying any file from skel directory into it.
Creating mailbox file: File exists
/usr/sbin/semanage: Linux User xguest does not exist
useradd: warning: the user name xguest to xguest_u SELinux user mapping failed.
+ semanage login -a -S targeted -s xguest_u xguest
/usr/sbin/semanage: Linux User xguest does not exist
+ semanage login -m -S targeted -s xguest_u xguest
/usr/sbin/semanage: Login mapping for xguest is not defined
+ exit 1

The work around is I manually create the ID "xguest" first. This allows me to install the package. Now, I'm running into a different problem, on one machine with proprietary nvidia driver installed, I'm having trouble to use the guest account. On a different machine with Intel video card, I don't have problem using the guest account, so far.

Another update. 
On the machine with nvidia card, I removed the proprietary driver and guest account works fine after that. Of course, this will cause different problem with the new GNOME 3. Oh well...

It looks like the useradd command was failing to add the xguest account, if there was a /home/xguest directory?

All of the other errors were caused by this?

What AVC were you seeing with the nvidia drivers?

I don't believe that's the case.  I've tried this with and without an existing xguest home directory and mailbox and it's failed each time.  It seems to me this came about with a recent change to the shadow-utils package or one of the selinux policy packages, as it was working ~ 2 or so weeks ago.

See #701355.

What AVC were you seeing with the nvidia drivers?
The following is the output of audit2allow -alr
require {
	type xguest_gkeyringd_t;
	type xguest_t;
	type namespace_init_t;
	type xdm_t;
}

#============= namespace_init_t ==============
files_rw_etc_files(namespace_init_t)

#============= xdm_t ==============
dev_rw_generic_chr_files(xdm_t)

#============= xguest_gkeyringd_t ==============
fs_getattr_tmpfs(xguest_gkeyringd_t)

#============= xguest_t ==============
accountsd_dbus_chat(xguest_t)
dev_rw_generic_chr_files(xguest_t)
rpm_dbus_chat(xguest_t)

I also have the audit log attached.

Created attachment 513328 [details]
Audit log

The problem is /dev/nvidiactl is labeled incorrectly.  If you run restorecon on it, the label should be fixed and everything should work properly.

Weird, I swear I did "touch /.autorelabel;reboot" when I run into the problem. I will try it again later today.
Thanks.

I relabeled the whole system again and still experience the same problem. 
[awang@mars ~]$ ls -lZ /dev/nvidiactl
crw-rw-rw-. root root system_u:object_r:device_t:s0    /dev/nvidiactl
Is there anything else you want me to check?

1. You could add /dev/nvidiactl to /etc/selinux/restorecond.conf and run the
restorecond service.

2. If  you see in the scripts where nvidiactl is created, you could add a
restorecon right afterwards.

3. Or you can add a local policy module using

# grep gnome-session-c /var/log/audit/audit.log | audit2alllow -M
nvidiaisbroken
# semodule -i nvidiaisbroken.pp

Daniel

Are there any updates/progress to report in regards to failed xguest installation?

Thanks

Is there any improvement on this ?
I've reproduced the error on intel GPU on i686.

I'm running with selinux enforcing.
# semanage user -a  -S targeted -P xguest -R xguest_r xguest_u
# echo $?
0
# useradd -c "Guest" -Z xguest_u xguest
useradd: warning: the home directory already exists.
Not copying any file from skel directory into it.
Creating mailbox file: File exists
/usr/sbin/semanage: Linux User xguest does not exist
useradd: warning: the user name xguest to xguest_u SELinux user mapping failed.

But creating the user without the SE context, then adding the SE context worked:
# useradd -c "Guest" xguest
# usermod -Z xguest_u  xguest
yum localinstall xguest

(It has just taken more than 5min to install on my Atom N450).

Other unrelated remark, is it possible to localize the user comment.
I'm using usermod -c 'Invité' xguest

I confirm the problem on a freshly installed Fedora 15, and the work around of comment #20.

I believe a useradd package has just been pushed to fix this problem.

Fixed for me, I think that should be closed as duplicate of #701355

*** This bug has been marked as a duplicate of bug 701355 ***