I was going to upgrade a machine from SL6 to SL7 in stages, temporarily dual-booting until I had the SL7 installation customized.  As a first step, I wanted to set up an SL7 root on an unused partition.  So I ran the SL7 installer, telling it NOT to install a boot loader.  I thought that if it wasn't going to install a boot loader, I could safely nominate the same boot partition that I used for booting SL6.  WRONG!  

Although the installer didn't write to the mbr and didn't put the files necessary for booting with grub2 into the /boot/grub2 directory, it did overwrite the initramfs files for the installed SL6 kernels,  replacing them with ones presumably suitable for booting with grub2, and leaving the machine unbootable with legacy grub until rescued with a live cd.

This strikes me as unreasonable behavior on the part of the installer.  Why convert existing files for grub2 if you aren't setting up the machine to boot with grub2?  What is more, experimentation with virtual machines has shown that if I do install a boot loader, the lines in the grub.cfg menu for booting the SL6 kernels with grub2 don't work anyway, so the whole exercise of converting the initramfs files seems pretty pointless.

Stephen Isard