Hi folks,

I have Alpine Linux installed in an encrypted LUKS partition. I came across this tutorial which shows how to setup a key in a USB drive and when the drive is inserted and the computer booted, the LUKS partition auto-unlocks with the key on the USB drive.

https://askubuntu.com/questions/1414617/configure-ubuntu-22-04-zfs-for-automatic-luks-unlock-on-boot-via-usb-drive

I would like to setup the same thing but I do not have Alpine linux installed on ZFS, so I’m looking for ways to adapt the instructions.

So far, what I’ve done is:

  1. I’ve setup the key on the usb stick and I can unlock the LUKS partition with that key.
  2. create a /etc/mkinitfs/features.d/usb-unlock.sh script with the following content:

(the echo to /dev/kmesg was to check whether the script did indeed run at boot by trying to print to the kernel messages but I can’t find anything in the kernel messages).

#!/bin/sh

echo "usb-unlock script starting..." > /dev/kmsg

USB_MOUNT="/mnt/my-usb-key" # The USB stick mounting point
LUKS_KEY_FILE="awesome.key"  # The name of your keyfile on the USB stick

# Search for the USB stick with the key
for device in $(ls /dev/disk/by-uuid/*); do
    mount $device $USB_MOUNT 2>/dev/null
    if [ -f "$USB_MOUNT/$LUKS_KEY_FILE" ]; then
        # Unlock the LUKS partition
        cryptsetup luksOpen /dev/sda3 cryptroot \
            --key-file "$USB_MOUNT/$LUKS_KEY_FILE" && exit 0
    fi
    umount $USB_MOUNT
done
echo "No USB key found, falling back to password prompt." # this message never appears, despite not having found the key on the usb stick

echo "usb-unlock script ending." > /dev/kmsg
  1. I added usb-unlock to the features in mkinitfs.conf:
mytestalpine:~# cat /etc/mkinitfs/mkinitfs.conf 
features="ata base ide scsi usb virtio ext4 cryptsetup keymap usb-unlock"
  1. run mkinitfs to rebuild the initramfs. Then reboot to test the implementation, which was unsuccessful.

What am I missing / doing wrong? Thank you for your help!

Edit: forgot to add step 4

  • The Hobbyist@lemmy.zipOP
    0·
    28 days ago

    Thank you for your help. I spent time digging into this rabbit hole, and while I’ve learned a lot, I am struggling to get the basics to work. Right now, I’m focusing on being able to just boot an image I created using dracut, excluding all the initial stuff I wanted, just be able to reproduce the original functionality of being able to unlock my luks partition using my keyboard.

    Where I’m at: I am building my initramfs using the following command: dracut -f -v --add crypt --add lvm --add dm. I get the following output log:

    Output log

    mytestalpine:~# dracut -f -v --add crypt --add lvm --add dm dracut[I]: Executing: /usr/bin/dracut -f -v --add crypt --add lvm --add dm dracut[I]: Module ‘dash’ will not be installed, because command ‘dash’ could not be found! dracut[I]: Module ‘mksh’ will not be installed, because command ‘mksh’ could not be found! dracut[I]: Module ‘caps’ will not be installed, because command ‘capsh’ could not be found! dracut[I]: Module ‘modsign’ will not be installed, because command ‘keyctl’ could not be found! dracut[I]: Module ‘i18n’ will not be installed, because command ‘loadkeys’ could not be found! dracut[I]: Module ‘url-lib’ will not be installed, because command ‘curl’ could not be found! dracut[I]: Module ‘btrfs’ will not be installed, because command ‘btrfs’ could not be found! dracut[I]: Module ‘dmraid’ will not be installed, because command ‘dmraid’ could not be found! dracut[I]: Module ‘dmsquash-live-ntfs’ will not be installed, because command ‘ntfs-3g’ could not be found! dracut[I]: Module ‘mdraid’ will not be installed, because command ‘mdadm’ could not be found! dracut[I]: Module ‘crypt-gpg’ will not be installed, because command ‘gpg’ could not be found! dracut[I]: Module ‘cifs’ will not be installed, because command ‘mount.cifs’ could not be found! dracut[I]: Module ‘iscsi’ will not be installed, because command ‘iscsi-iname’ could not be found! dracut[I]: Module ‘iscsi’ will not be installed, because command ‘iscsiadm’ could not be found! dracut[I]: Module ‘iscsi’ will not be installed, because command ‘iscsid’ could not be found! dracut[I]: 95nfs: Could not find any command of ‘rpcbind portmap’! dracut[I]: Module ‘nvmf’ will not be installed, because command ‘nvme’ could not be found! dracut[I]: Module ‘nvmf’ will not be installed, because command ‘jq’ could not be found! dracut[I]: Module ‘biosdevname’ will not be installed, because command ‘biosdevname’ could not be found! dracut[I]: Module ‘masterkey’ will not be installed, because command ‘keyctl’ could not be found! dracut[I]: Module ‘dash’ will not be installed, because command ‘dash’ could not be found! dracut[I]: Module ‘mksh’ will not be installed, because command ‘mksh’ could not be found! dracut[I]: Module ‘caps’ will not be installed, because command ‘capsh’ could not be found! dracut[I]: Module ‘modsign’ will not be installed, because command ‘keyctl’ could not be found! dracut[I]: Module ‘url-lib’ will not be installed, because command ‘curl’ could not be found! dracut[I]: Module ‘btrfs’ will not be installed, because command ‘btrfs’ could not be found! dracut[I]: Module ‘dmraid’ will not be installed, because command ‘dmraid’ could not be found! dracut[I]: Module ‘dmsquash-live-ntfs’ will not be installed, because command ‘ntfs-3g’ could not be found! dracut[I]: Module ‘mdraid’ will not be installed, because command ‘mdadm’ could not be found! dracut[I]: Module ‘crypt-gpg’ will not be installed, because command ‘gpg’ could not be found! dracut[I]: Module ‘cifs’ will not be installed, because command ‘mount.cifs’ could not be found! dracut[I]: Module ‘iscsi’ will not be installed, because command ‘iscsi-iname’ could not be found! dracut[I]: Module ‘iscsi’ will not be installed, because command ‘iscsiadm’ could not be found! dracut[I]: Module ‘iscsi’ will not be installed, because command ‘iscsid’ could not be found! dracut[I]: 95nfs: Could not find any command of ‘rpcbind portmap’! dracut[I]: Module ‘nvmf’ will not be installed, because command ‘nvme’ could not be found! dracut[I]: Module ‘nvmf’ will not be installed, because command ‘jq’ could not be found! dracut[I]: Module ‘masterkey’ will not be installed, because command ‘keyctl’ could not be found! dracut[I]: *** Including module: sh *** dracut[I]: *** Including module: busybox *** dracut[I]: *** Including module: crypt *** dracut[I]: *** Including module: dm *** dracut[D]: Skipping udev rule: 10-dm.rules dracut[D]: Skipping udev rule: 13-dm-disk.rules dracut[D]: Skipping udev rule: 95-dm-notify.rules dracut[D]: Skipping udev rule: 64-device-mapper.rules dracut[D]: Skipping udev rule: 60-persistent-storage-dm.rules dracut[D]: Skipping udev rule: 55-dm.rules dracut[I]: *** Including module: kernel-modules *** dracut[I]: *** Including module: kernel-modules-extra *** dracut[D]: kernel-modules-extra: configuration source “/run/depmod.d” does not exist dracut[D]: kernel-modules-extra: configuration source “/etc/depmod.d” does not exist dracut[D]: kernel-modules-extra: configuration source “/lib/depmod.d” does not exist dracut[I]: *** Including module: lvm *** dracut[D]: Skipping udev rule: 11-dm-lvm.rules dracut[D]: Skipping udev rule: 64-device-mapper.rules dracut[D]: Skipping udev rule: 56-lvm.rules dracut[D]: Skipping udev rule: 60-persistent-storage-lvm.rules dracut[I]: *** Including module: rootfs-block *** dracut[I]: *** Including module: terminfo *** dracut[I]: *** Including module: udev-rules *** dracut[D]: Skipping udev rule: 70-persistent-net.rules dracut[I]: *** Including module: usrmount *** dracut[I]: *** Including module: base *** dracut[I]: *** Including module: fs-lib *** dracut[I]: *** Including module: shutdown *** dracut[I]: *** Including modules done *** dracut[I]: *** Installing kernel module dependencies *** dracut[I]: *** Installing kernel module dependencies done *** dracut[I]: *** Resolving executable dependencies *** dracut[I]: *** Resolving executable dependencies done *** dracut[I]: *** Hardlinking files *** dracut[D]: Mode: real dracut[D]: Method: sha256 dracut[D]: Files: 457 dracut[D]: Linked: 0 files dracut[D]: Compared: 0 xattrs dracut[D]: Compared: 6 files dracut[D]: Saved: 0 B dracut[D]: Duration: 0.015759 seconds dracut[I]: *** Hardlinking files done *** dracut[I]: Could not find ‘strip’. Not stripping the initramfs. dracut[I]: *** Generating early-microcode cpio image *** dracut[I]: *** Store current command line parameters *** dracut[I]: Stored kernel commandline: dracut[I]: rootfstype=ext4 rootflags=rw,relatime dracut[E]: ldconfig exited ungracefully dracut[I]: *** Creating image file ‘/boot/initramfs-6.6.56-0-lts.img’ *** dracut[I]: Using auto-determined compression method ‘gzip’ dracut[D]: Image: /var/tmp/dracut.Ds3W3x/initramfs.img: 12M dracut[D]: ======================================================================== dracut[D]: Version: dracut-060 dracut[D]: lib/dracut/dracut-060 dracut[D]: dracut[D]: Arguments: -f -v --add ‘crypt’ --add ‘lvm’ --add ‘dm’ dracut[D]: lib/dracut/build-parameter.txt dracut[D]: dracut[D]: dracut modules: dracut[D]: sh dracut[D]: busybox dracut[D]: crypt dracut[D]: dm dracut[D]: kernel-modules dracut[D]: kernel-modules-extra dracut[D]: lvm dracut[D]: rootfs-block dracut[D]: terminfo dracut[D]: udev-rules dracut[D]: usrmount dracut[D]: base dracut[D]: fs-lib dracut[D]: shutdown dracut[D]: lib/dracut/modules.txt dracut[D]: ========================================================================

    <Truncanted due to char limit>

    Then I updated the /boot/extlinux.conf file, adding the following second entry (displaying the first one just for comparison):

    LABEL lts
  MENU DEFAULT
  MENU LABEL Linux lts
  LINUX vmlinuz-lts
  INITRD initramfs-lts
  APPEND root=/dev/mapper/root modules=sd-mod,usb-storage,ext4 cryptroot=<my-uuid> cryptdm=root quiet rootfstype=ext4

LABEL lts
  MENU LABEL dracut-img
  LINUX vmlinuz-lts
  INITRD /boot/initramfs-6.6.56-0-lts.img
  APPEND root=/dev/mapper/root modules=sd-mod,usb-storage,ext4 cryptroot=UUID=<my-uuid> cryptdm=root quiet rootfstype=ext4 rootflags=rw,relatime

    I added the rootflags=rw,relatime because this was shown in the dracut log, so I thought perhaps that mattered. But for the most part I left it the same as the previous entry, because I’m trying to do the same thing I suppose. Perhaps I’m mistaken?

    The current result of booting that image leads to a long loading (not asking for the passphrase to unlock the partition) then displaying the following error:

    dracut Warning: Could not boot.

dracut Warning: "/dev/mapper/root" does not exist

Generating "/run/initramfs/rdsosreport.txt"
You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or /boot after mounting them and attach it to a bug report.

To get more debug information in the report, reboot with "rd.debug" added to the kernel command line.

Dropping to debug shell.

    Before dropping me in a shell, in which I have not found anything useful to do. I am surely missing something basic as my understanding of what’s happening is pretty superfluous.

    What I’m noticing which may be of importance:

    • dracut[E]: ldconfig exited ungracefully, in the dracut output log. Perhaps this matters and should be fixed? An image is nonetheless generated.
    • there are many missing modules when creating an image, but I don’t know if any of them matter, at least for my purpose.
    • One thing I can’t wrap my head around is, how come the original kernal image work, when I had packages such as device-mapper and lvm missing, why did dracut complain about them missing for me to compile my own image? and would I need to add options in the /boot/extlinux.conf file, when they are not required for the original boot entry, when all I’m trying to do (as a start) is just make sure I can reproduce a bootable kernel image?
    • chameleon@fedia.io
      2·
      27 days ago

      I think you should check your root= line and add a rd.luks.uuid= to make it open it. Dracut will by default open the root FS as /dev/mapper/luks-abcdef... based on the LUKS container UUID. You can get that with cryptsetup luksUUID. /dev/mapper/root is just never going to show up unless you’ve assigned a custom name to that with the barely documented rd.luks.name, and I don’t see that in your setup. The cryptroot and cryptdm parameters aren’t used by Dracut either.

      With all of that missing it’s just gonna wait for that /dev/mapper/root to magically show up out of nowhere, without ever trying to open it.

      A correct cmdline will probably look something along the lines of root=/dev/mapper/luks-<uuid> modules=sd-mod,usb-storage,ext4 rootfstype=ext4 rootflags=rw,relatime rd.luks.uuid=<uuid> and once opening with passphrase works, you can start to mess with rd.luks.key=/awesome.key (and readd quiet when done debugging, if you want it that way).

      ldconfig errors and the missing modules should be fine. musl’s ldconfig is just a bit different but also isn’t required in quite the same way. I don’t think you should need to mess with modules manually. I don’t think you’re using LVM’s userland for your setup, just all the device-mapper kernel modules. Dracut will pull all the necessary bits in for you if you’re setting it up for LUKS.