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1. Append this to the kernel line in /etc/grub.conf
blacklist=nouveau
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Make sure you are editing the correct kernel line. If you are not sure, you can add it to all the kernel lines.
2. Also, add the following to /etc/modprobe.d/blacklist.conf
blacklist
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nouveau
options nouveau modeset=0
3. Rebuild initial ram disk. For example, if your kernel is 2.6.32-573.22.1.el6.x86_64, then do this:...
# dracut -f /boot/initramfs-2.6.32-573.22.1.el6.x86_64.img 2.6.32-573.22.1.el6.x86_64 -v
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