无法在带rEFInd的2017款iMac上从外置硬盘LUKS/LVM组启动Ubuntu

Hey there, I’ve worked through similar encrypted external drive boot issues on Macs with rEFInd, so let’s get your Ubuntu setup running. Here’s a step-by-step breakdown of the fixes you’ll need to apply:

1. Ensure rEFInd Has the Right Modules Loaded #

rEFInd needs specific modules to handle LUKS encryption and LVM volumes. Here’s how to enable them:

• Boot into macOS and open the rEFInd configuration file (usually at /Volumes/ESP/EFI/refind/refind.conf — you may need to mount the EFI partition first with diskutil mount /dev/disk0s1).
• Find the line starting with #modules and uncomment/modify it to include:

  modules luks lvm ext4
  

• If you’re using LUKS2 encryption (check with cryptsetup status /dev/sdXn in Ubuntu live mode), make sure your rEFInd version is 0.12.0 or newer — older versions don’t support LUKS2. You can check your version by running refind-install --version in macOS Terminal, and update rEFInd if needed.

2. Fix Ubuntu’s Initramfs (Critical for Encrypted Boot) #

The most common issue is that Ubuntu’s initramfs doesn’t include the drivers to unlock LUKS and detect LVM volumes at boot. To fix this:

• Boot from your Ubuntu live USB and open a Terminal.
• First, unlock your LUKS partition (replace /dev/sdXn with your encrypted partition’s device path, e.g., /dev/sdb2):

  cryptsetup luksOpen /dev/sdXn cryptroot
  

• Activate the LVM volume group:

  vgchange -ay
  

• Mount your Ubuntu root partition (replace vg-name and lv-root with your actual volume group and logical root partition names — find them with lvdisplay):

  mount /dev/mapper/vg-name-lv-root /mnt
  

• Mount critical system directories to chroot into your installed Ubuntu:

  mount --bind /dev /mnt/dev
  mount --bind /proc /mnt/proc
  mount --bind /sys /mnt/sys
  

• Enter the chroot environment:

  chroot /mnt
  

• Update the initramfs to include LUKS/LVM drivers:

  update-initramfs -u -k all
  

• Verify your /etc/crypttab has the correct entry (replace xxxx-xxxx with your LUKS partition’s UUID, found via blkid):

  cryptroot UUID=xxxx-xxxx none luks,discard
  

• Exit chroot and reboot:

  exit
  reboot
  

3. Add a Custom rEFInd Menu Entry (Optional but Reliable) #

Sometimes rEFInd auto-detection misses encrypted LVM setups. Adding a manual menu entry ensures it can find your kernel and initrd:

• In macOS, create a new file at /Volumes/ESP/EFI/refind/refind.conf.d/ubuntu.conf (create the refind.conf.d folder if it doesn’t exist).
• Add the following entry, replacing placeholders with your system’s details:

  menuentry "Ubuntu (LUKS/LVM)" {
      icon     /EFI/refind/icons/os_linux.png
      volume   "Ubuntu"  # Name of your external drive's volume (optional)
      loader   /vmlinuz-5.15.0-78-generic  # Replace with your actual kernel version
      initrd   /initrd.img-5.15.0-78-generic  # Match the kernel version
      options  "cryptdevice=UUID=xxxx-xxxx:cryptroot root=/dev/mapper/vg-name-lv-root ro quiet splash"
  }
  

• Save the file, then reboot and select this new entry from the rEFInd menu. You’ll be prompted to enter your LUKS password — enter it, and Ubuntu should boot.

4. Double-Check USB and Partition Setup #

• Ensure your external drive is connected to a USB 3.0 port on the iMac (avoid USB-C hubs if possible, as they can cause boot issues).
• Confirm your drive uses a pure GPT partition table (no hybrid MBR) — you can verify this in macOS Disk Utility (enable "Show All Devices" in the View menu, then check the drive’s partition scheme).

内容的提问来源于stack exchange，提问作者Bri Bri