“The Red Hat Enterprise Linux installation tree in that directory does not seem to match your boot media”

In working with Red Hat Satellite Server 5.4.1, we had a problem with Dell PowerEdge R720 servers.  When we kickstarted those systems to RHEL 5.7, using DHCP, the Tigon3 NIC would flap at the point where the installer enables the NIC to get stage2.img, and DHCP would time out.

While troubleshooting this, I updated the kickstart tree to RHEL 5.8 (as a sidepoint to this post, that worked).  But alas, that tree wanted packages that are too new for RHEL 5.7 (I was hoping we could install RHEL 5.7 from the RHEL 5.8 kickstart images, but no).  So I reverted back to the previous kickstart images, and got the above error.

I found the problem by comparing files from /var/satellite/rhn/kickstart/my-installation-tree with /tftpboot/images/my-installation-tree.  I found that the two files in the latter directory (vmlinuz and initrd.img) were the same ones from the base tree for RHEL 5.8 (I did not change them initially, so I assume “cobbler sync” did).  They should have been the ones from the RHEL 5.7 tree.  So, when I copied the correct ones in and re-ran “cobbler sync“, we were good.

Lesson learned: vmlinuz and initrd.img in
/var/satellite/rhn/kickstart/my-installation-tree/images/pxeboot

and in
/tftpboot/images/my-installation-tree/ks-rhel-x86_64-server-5-57
must match