GRUB question

[Volker Wysk]

Am Sonntag, 8. Oktober 2017, 12:11:41 CEST schrieb 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.

I think, the necessary command is "update-initramfs -u". I get the following 
message:

cryptsetup: WARNING: target sdb2_crypt uses a key file, skipped

Looks like you can't use a keyfile when setting up sdb2_crypt, which is needed 
for setting up the root LV. It's a hen or egg problem. How can I specify a 
password for sdb2_crypt? I's okay when it's the same as for sda5_crypt, the PV 
of the root LV. But I don't want to enter two passwords at bootup.

Bye
Volker