GRUB doesn't find /boot in LVM

Question

My system was installed with the Antergos installer and it runs encrypted GRUB. This works fine, just have to insert decryption key twice.

Then I added LVM and created three LVM volumes, boot root and swap. Now I want to update my GRUB with this LVM setup so I can choose to boot the second OS from LVM or just boot Arch.

NAME                                            MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                                               8:0    0 465.8G  0 disk  
├─sda1                                            8:1    0  65.2G  0 part  
│ └─luks                                        254:0    0  65.2G  0 crypt /
├─sda2                                            8:2    0   3.7G  0 part  
│ └─luks-14a10aeb-01ec-44f4-b908-0c09685a03ed   254:4    0   3.7G  0 crypt /run/media/thijs/74ec47c2-64ed-4fe5-a965-a5e414b7a129
└─sda3                                            8:3    0 396.9G  0 part  
  ├─triagia-kaliboot                            254:1    0   500M  0 lvm   /run/media/thijs/f1eb6904-c17e-40b7-8740-60e67b8d04de
  ├─triagia-kaliroot                            254:2    0    50G  0 lvm   
  │ └─luks-26028d27-8a95-41c3-9d80-9415b8c170dc 254:6    0    50G  0 crypt /run/media/thijs/65c769fd-ea4a-4854-928c-3c28f15745aa
  └─triagia-kaliswap                            254:3    0     4G  0 lvm   
    └─luks-a0fa8f9e-e6d0-42d7-b54c-7c275ddc328a 254:5    0     4G  0 crypt 

But when I use grub-mkconfig, the script never finds the boot partition in the LVM. I've used vgscan and vgchange to make them active and mounted the LVM volumes but still grub-mkconfig only reports the boot on sda1.

Research points a lot to taking /boot out of the LVM but I don't like that. I'd add the needed GRUB config manually but I couldn't find an example.

Volumes:

  --- Logical volume ---
  LV Path                /dev/triagia/kaliboot
  LV Name                kaliboot
  VG Name                triagia
  LV UUID                e68eqU-zP3Q-YnwY-ds6M-MG34-zAB5-VhZcAQ
  LV Write Access        read/write
  LV Creation host, time conDoin, 2015-08-21 17:50:52 +0200
  LV Status              available
  # open                 0
  LV Size                500.00 MiB
  Current LE             125
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:0

  --- Logical volume ---
  LV Path                /dev/triagia/kaliroot
  LV Name                kaliroot
  VG Name                triagia
  LV UUID                Bco7iM-ZlQR-NyeI-Nl1r-N1IK-kooC-oBCfV6
  LV Write Access        read/write
  LV Creation host, time conDoin, 2015-08-21 17:51:09 +0200
  LV Status              available
  # open                 0
  LV Size                50.00 GiB
  Current LE             12800
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:1

  --- Logical volume ---
  LV Path                /dev/triagia/kaliswap
  LV Name                kaliswap
  VG Name                triagia
  LV UUID                POkVXd-UMoe-yHaB-nfrV-lbpO-Fv3l-86N7AT
  LV Write Access        read/write
  LV Creation host, time conDoin, 2015-08-21 17:54:32 +0200
  LV Status              available
  # open                 0
  LV Size                4.00 GiB
  Current LE             1024
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:2

After some extra-extra reading on the Arch forums I've added lvm2 to mkinitcpio.conf under HOOKS.

HOOKS="base udev autodetect modconf block keyboard keymap encrypt resume lvm2 filesystems fsck"

And then I ran again:

mkinitcpio -p linux
systemctl enable lvm2-lvmetad.service
grub-mkconfig -o /boot/grub/grub.cfg

But this didn't change anything.

Boot volume

drwxr-x---+ 4 root root       80 Aug 23 19:19 ..
drwxr-xr-x  4 root root     1024 Aug 21 18:18 .
-rw-r--r--  1 root root 19692558 Aug 21 18:18 initrd.img-4.0.0-kali1-amd64
drwxr-xr-x  2 root root     1024 Aug 21 18:14 grub
drwx------  2 root root    12288 Aug 21 18:00 lost+found
-rw-r--r--  1 root root   165968 Jun  3 10:08 config-4.0.0-kali1-amd64
-rw-r--r--  1 root root  2790804 Jun  3 10:08 System.map-4.0.0-kali1-amd64
-rw-r--r--  1 root root  3274048 Jun  3 10:07 vmlinuz-4.0.0-kali1-amd64

grub dir:

drwxr-xr-x 4 root root    1024 Aug 21 18:18 ..
drwxr-xr-x 2 root root    1024 Aug 21 18:14 .
-rw-r--r-- 1 root root 2400500 Aug 21 18:14 unicode.pf2

I've created a manual Grub config in 40_custom and this almost works. The LVM is found and luks on root is decrypted but then I get this error:

Begin: Running /scripts/init-bottom ... mount: mounting /dev on /root/dev failed: No such file or directory
done.
No init found. Try passing init= bootarg.

Then I'm left with command line: (initramfs) _

Manual GRUB config:

menuentry 'Kali' {
insmod lvm
insmod gzio
insmod part_msdos
insmod ext2
set root=lvm/triagia-kaliboot
search --no-floppy --fs-uuid --set=root f1eb6904-c17e-40b7-8740-60e67b8d04de
linux /vmlinuz-4.0.0-kali1-amd64 root=/dev/mapper/triagia-kaliboot setkmap=us
initrd /initrd.img-4.0.0-kali1-amd64
}

Answer 1

You will need to add the kernel parameter in order for GRUB to decrypt the disk so that it can load your kernel.

Add command below into GRUB's kernel parameter:

cryptdevice=UUID=device-UUID:lvm root=/dev/mapper/MyVol-root
The <device-UUID> refers to the UUID of /dev/sdaX

Decrypt and then boot, that's it. For more information, please refer to Arch Wiki.