Instalação do ubuntu - dispositivo raiz montado com sucesso, mas / sbin / init não existe

Minha configuração:

Arch + Ubuntu 16.04 via Efi, Gpt, grub2

sda1                  -> efi boot
sda2                  -> encrypted, lvm on top
dev/mapper/vg-arch    -> my arch linux
dev/mapper/vg-ubuntu  -> my ubuntu installation

Arch está funcionando bem. Após a instalação do ubuntu, atualizei o grub, agora ambos são inicializáveis.

Problema: após a inicialização no Ubuntu, recebo o erro:

root device mounted successfully, but /sbin/init does not exist ubuntu

Editar 1:

/etc/default/grub

GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR='lsb_release -i -s 2> /dev/null || echo Debian'
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX="cryptdevice=/dev/sda2/luksvg"

antes:

grub-mkconfig -o /boot/grub/grub.cfg
grub-install --target=x86_64-efi --efi-directory=/boot --recheck

e:

grub.cfg

# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#
### BEGIN /etc/grub.d/00_header ###
insmod part_gpt
insmod part_msdos
if [ -s $prefix/grubenv ]; then
  load_env
fi
if [ "${next_entry}" ] ; then
   set default="${next_entry}"
   set next_entry=
   save_env next_entry
   set boot_once=true
else
   set default="0"
fi

if [ x"${feature_menuentry_id}" = xy ]; then
  menuentry_id_option="--id"
else
  menuentry_id_option=""
fi

export menuentry_id_option

if [ "${prev_saved_entry}" ]; then
  set saved_entry="${prev_saved_entry}"
  save_env saved_entry
  set prev_saved_entry=
  save_env prev_saved_entry
  set boot_once=true
fi

function savedefault {
  if [ -z "${boot_once}" ]; then
    saved_entry="${chosen}"
    save_env saved_entry
  fi
}

function load_video {
  if [ x$feature_all_video_module = xy ]; then
insmod all_video
  else
    insmod efi_gop
    insmod efi_uga
    insmod ieee1275_fb
    insmod vbe
    insmod vga
    insmod video_bochs
    insmod video_cirrus
  fi
}

if loadfont unicode ; then
  set gfxmode=auto
  load_video
  insmod gfxterm
  set locale_dir=$prefix/locale
  set lang=de_DE
  insmod gettext
fi
terminal_input console
terminal_output gfxterm
if [ x$feature_timeout_style = xy ] ; then
  set timeout_style=menu
  set timeout=5
# Fallback normal timeout code in case the timeout_style feature is
# unavailable.
else
  set timeout=5
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/10_linux ###
menuentry 'Arch Linux' --class arch --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    load_video
    set gfxpayload=keep
    insmod gzio
    insmod part_gpt
    insmod fat
    set root='hd0,gpt1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1     --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  9E14-B35F
    else
  search --no-floppy --fs-uuid --set=root 9E14-B35F
    fi
    echo    'Linux linux wird geladen …'
    linux   /vmlinuz-linux root=/dev/mapper/luksvg-arch rw     cryptdevice=/dev/sda2:luksvg quiet
    echo    'Initiale Ramdisk wird geladen …'
    initrd  /initramfs-linux.img
}
submenu 'Erweiterte Optionen für Arch Linux'     $menuentry_id_option     'gnulinux-advanced-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    menuentry 'Arch Linux, mit Linux linux' --class arch --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-linux-    advanced-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    load_video
    set gfxpayload=keep
    insmod gzio
    insmod part_gpt
    insmod fat
    set root='hd0,gpt1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1     --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  9E14-B35F
    else
      search --no-floppy --fs-uuid --set=root 9E14-B35F
    fi
    echo    'Linux linux wird geladen …'
    linux   /vmlinuz-linux root=/dev/mapper/luksvg-arch rw     cryptdevice=/dev/sda2:luksvg quiet
    echo    'Initiale Ramdisk wird geladen …'
    initrd  /initramfs-linux.img
}
menuentry 'Arch Linux, with Linux linux (fallback initramfs)'     --class arch --class gnu-linux --class gnu --class os     $menuentry_id_option 'gnulinux-linux-fallback-a677b991-e4a0-41ae-9711-b4716a2e977d' {
    load_video
    set gfxpayload=keep
    insmod gzio
    insmod part_gpt
    insmod fat
    set root='hd0,gpt1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt1     --hint-efi=hd0,gpt1 --hint-baremetal=ahci0,gpt1  9E14-B35F
    else
      search --no-floppy --fs-uuid --set=root 9E14-B35F
    fi
    echo    'Linux linux wird geladen …'
    linux   /vmlinuz-linux root=/dev/mapper/luksvg-arch rw cryptdevice=/dev/sda2:luksvg quiet
        echo    'Initiale Ramdisk wird geladen …'
        initrd  /initramfs-linux-fallback.img
    }
}

### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_linux_xen ###
### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/30_os-prober ###
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f  ${config_directory}/custom.cfg ]; then
  source ${config_directory}/custom.cfg
elif [ -z "${config_directory}" -a -f  $prefix/custom.cfg ]; then
  source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###

então pensei que talvez eu devesse colocar ganchos no Ubuntu como fiz no arch /etc/mkinitcpio.conf, mas como?

Edição 2:

o link $ ls -l /sbin/initestá lá ...

Eu tenho um link simbólico de /sbin/initpara /lib/systemd/systemdna minha instalação do kubuntu. Talvez apenas tente criar esse link simbólico na sua máquina também? Veja como fica na minha máquina:

$ ls -l /sbin/init
lrwxrwxrwx 1 root root 20 Nov 24 13:21 /sbin/init -> /lib/systemd/systemd