initramfs for LVM

This is a simple initramfs for booting Linux from a root filesystem in an LVM volume. It is meant to be included in the kernel image.

Setup

• Download init and initramfs.list into the directory /usr/src/sys/initramfs.lvm
• Adjust your kernel source configuration under General setup select Initial RAM filesystem and RAM disk (initrams/initrd) support
• Enter /usr/src/sys/initramfs.lvm/initramfs.list as Initramfs source file(s):
  
• Exit and save your kernel configuration
• (Re-)Build your kernel, e.g.:

  $ make -j8 bzImage
  $ make modules

• Install the kernel:

  $ sudo cp arch/`uname -m`/boot/bzImage /boot/vmlinuz
  $ sudo make modules_install

• Your /boot/grub/grub.cfg may be very simplistic:

  set timeout=5
  set root=(lvm/vg00-lvroot)
  
  insmod part_msdos
  insmod part_gpt
  insmod lvm
  insmod linux
  
  menuentry "Linux" {
    linux /boot/vmlinuz root=/dev/mapper/vg00-lvroot
  }

• You may add rootflags=... followed by comma-separated mount options for the root filesystem. Defaults to ro,noatime,nodiratime
• Likewise, rootfstype=... explicitly instructs the kernel that the root volume contains the given filesystem
• If you add dorescue to the kernel commandline, you will be dropped to a rescue shell inside the initramfs