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Description of problem:
setting the onlyn to e.g 5 result in installation of 4 kernels. On  
installation of the 5th every already installed kernel but the running kernel  
in removed.  
I think this is due to the design of the break condition in the 
postresolve_hook function in installonlyn.  
The variable numleft will already be 0 before decrementing when on 
installation of the last kernel of the preselected set size. 
  
   

Version-Release number of selected component (if applicable):
2.5.0.5

How reproducible:
Sometimes

Steps to Reproduce:
1. set to_keep=4 (/etc/yum/pluginconf.d/installonlyn.conf) 
2. install a kernel (no 1, in adition to the running kernel)  
3. install a kernel (no 2)  
4. install a kernel (no 3)  
     

Actual Results:  Only 2 kernels are installed (the running + the newest) 

Expected Results:  The preset to_keep number of kernels present: only the oldest dropped   
when the "desired" count would have been exceeded.  

Additional info:

reproducibility: this happens on istallation of every (n-1)'th kernel (with  
to_keep=n) - if I got the arithmetic right.