An attempt to do this fails:
[root@gatekeeper rpm]# yum update > /tmp/out 2>&1 &
Nothing is written to /tmp/out, so there is no clear indication that yum is
The only way to kill yum is with -9.
This works for me here. You may be hitting the point where it prompts and it's
not flushing the output. Try using yum -y.