[Yum] /var/lock/subsys/yum doesn't exist

[jtate at dragonstrider.com (Joseph Tate)]

I've got a server that is not getting updates unless I manually run yum 
update.  This I've traced to my /etc/cron.daily/yum.cron file which says:
#!/bin/sh

if [ -f /var/lock/subsys/yum ]; then
        /usr/bin/yum -R 10 -e 0 -d 0 -y update yum
        /usr/bin/yum -R 120 -e 0 -d 0 -y update
fi

The problem is that /var/lock/subsys/yum doesn't exist.  How is it 
supposed to be created?  Is it supposed to be part of the RPMS?  Should 
that test be negated?  I'm using yum-2.0.3-1 on a RHL 9 system.  
Manually running the cron script returns immediately.  Creating the file 
seems to work, but the lock is removed at some point, and after that yum 
won't run from cron.

Joseph