I had a CentOS 4.1 installation (LVM over RAID1), and tried to do an update to the 4.3 release. Nothing too fancy, I did all the partitions with the graphical installer for the 4.1 Version. First, the installer did not find the previos installation, then I tried with the "upgradeany" option to the kernel, and from there the update ran apparently with no problem. When the boot loader section came, the setup was not able to find the previous working grub configuration, and the "update boot loader" option was disabled, so I marked the "new boot loader configuration" (don't remember the exact string. Then the installation process ended, and I did reboot. The "classic" "Error 15: File not found", from grub came. The description line was indeed, for the 2.6.9-34 (centos 4.3's relase), but I could not boot the system. I went into the "linux rescue" and from there, I started to find out some more weird stuff. First, the kernel package was not installed correctly, the files. /boot/* and /lib/modules/* weren't there, there was no entry on the rpm database, in fact the only probe that the kernel was "installed" was the grub entry. I tried to rebuild my old grub configuration, and boot with the previous kernel version I had. (The rescue disk, did not let me mount the cdrom, and I was without Internet to find out how to enable de /dev entry to acomplish the task). With the old kernel config, I could start my server, but I could not login from the console (tty*). Then I had to reboot in single mode, and from there perform the kernel installation from the 4.3's cdrom. /var/log/messages had this line for every login attempt: login [1234]: Module unknown. As this is a production server, I checked for all the services (ldap, samba, mysql, apache, etc.) and there where all working fine. I could log in from sshd without any problem (besides the bunch I'm writing here of course). Finally, when I checked on all the services and the console login problem, the rest was working as before. I went then to the "yum check-update", and found some "pam-*" update, so I did the corresponding "yum update". After pam's update, I could login again from the console, by the way "crond" tasks weren't working either, when console login was not working. That is not the end of this Crypt's Tale :( Now I have the system, running 4.3, yum does not report any update, but I have several duplicated rpm installed. :( I'm willing to try all this again, in a VMware, just to convince myself that I'm not crazy, and that ghosts does not exist :) upgrade.log has several lines like this: Upgrading kernel-2.6.9-34.EL.i686. error: %pre(kernel-2.6.9-34.EL.i686) scriptlet failed, exit status 255 error: install: %pre scriptlet failed (2), skipping kernel-2.6.9-34.EL Upgrading kernel-smp-2.6.9-34.EL.i686. error: %pre(kernel-smp-2.6.9-34.EL.i686) scriptlet failed, exit status 255 error: install: %pre scriptlet failed (2), skipping kernel-smp-2.6.9-34.EL where the pre-install script fail, but how come the installer did not reported any problem during installation? I'm not a newbie, I have quite a while working with linux, and I just want to aware people who are going to perform an update, skipping some version in between or perhaps moving to 4.3 to be very carefull in the process. I think this was a experience that was worth telling and researching to find out what really happend. Best Regards Ale