Warning: Unable to open /dev/fd0 read-write (Read-only file system). /dev/fd0 has been opened read-only.
That's a very annoying error, it's simply because Centos for some reason thinks it's wise to load the "floppy" kernel module, who has a floppy drive? I haven't seen or used a floppy for over 12 years!
It's more than just annoying, if you probe the drives attached to your system, eg. with grub or partprobe, it keeps trying to locate a floppy dirve that doesn't exist and literally takes a few minutes to let you complete the task of grub or partprobe or related commands.
That takes effect right away,now grub will load right away and partprobe will take a few seconds at most.
You'll also want to prevent it from loading again in the future at boot time:
echo "alias floppy off" >> /etc/modprobe.conf
For Debian based Distros
echo "blacklist floppy" >> /etc/modprobe.d/blacklist
The command above tells the kernel not to load the "floppy" module ever again by adding "blacklist floppy" to the blacklist list.
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