GRUB question

[Volker Wysk]

Hi!

I'm trying to set up an SSD cache for my hard disk. Just in a virtual machine, 
so far.

It's for my (encrypted) root filesystem. According to the instructions 
(https://www.thomas-krenn.com/de/wiki/LVM_Caching_mit_SSDs_einrichten), the 
following is needed when the root filesystem is to be cached. Otherwise, it 
won't be able to boot:

echo "dm_cache" >> /etc/initramfs-tools/modules
echo "dm_cache_mq" >> /etc/initramfs-tools/modules
echo "dm_persistent_data" >> /etc/initramfs-tools/modules
echo "dm_bufio" >> /etc/initramfs-tools/modules

Now, how do I make this take effect? "grub-install /dev/sda" doesn't do it, 
"update-grub" also doesn't. (Yes, I'm just guessing.)

When I boot the virtual machine, I get a shell, with "(initramfs) " as the 
prompt, and a status message about busybox.

Thnx
Volker