Arch Linux

Whef

Member

Registered: 2012-08-26

Posts: 33

UX31A BIOS boot?

Problem

The SSD is no longer recognized in BIOS as a bootable device.

Hypothesis

You can't use BIOS boot with this laptop (you have to use UEFI). This is reinforced by the fact that every guide and post I've seen has been for UEFI boot. So, if you can do BIOS boot (and I'm just doing something wrong), why does everyone use UEFI? On the other hand, what would make it incapable of booting with BIOS?

Context

I'm just switching to Linux for the first time from Windows (though I've had some experience with Linux previously). In preparation I installed Arch Linux several times on VirtualBox, successfully.

Setup

ASUS Zenbook Prime UX31A-DB71
BIOS+GPT+GRUB2+LUKS+dm-crypt

Here is a complete list of the steps (psuedo-code, mostly) I have taken (which worked in VirtualBox):

• Partition the system

gdisk /dev/sda
    n \n \n +2M EF02 # BIOS Boot Partition; https://wiki.archlinux.org/index.php/GRUB#GPT_specific_instructions
    n \n \n +200M \n # /boot partition (because of encryption)
    n \n \n (default - 4096) \n # root partition; leaves 2MiB (4096 sectors) for the recovery information
                                # see the note here: https://wiki.archlinux.org/index.php/GPT#Convert_from_MBR_to_GPT
    w

• Format the system

mkfs -t ext4 /dev/sda{2,3}
cryptsetup -c aes-xts-plain64 -y -s 512 luksFormat /dev/sda3
cryptsetup luksOpen /dev/sda3 root # Maps an unecrypted sda3 to /dev/mapper/root.
mkfs -t ext4 /dev/mapper/root

• Mount the partitions

mount /dev/mapper/root /mnt
mkdir /mnt/boot
mount /dev/sda2 /mnt/boot

• Install the system

pacstrap /mnt base base-devel grub-bios gnome vim systemd systemd-arch-units sudo

• Configure the system

genfstab /mnt -p -U >> /mnt/etc/fstab
arch-chroot /mnt
echo arch > /etc/hostname

# locale
ln -s /usr/share/zoneinfo/US/Pacific /etc/localtime
vim /etc/locale.conf
    LANG="en_US.UTF-8"
    LC_COLLATE="C"
vim /etc/locale.gen
     en_US.UTF-8
locale-gen

# mkinitcpio
vim /etc/mkinitcpio.conf
    HOOKS="... encrypt filesystems ..."
mkinitcpio -p linux

# grub
modprobe dm-mod
grub-install --target=i386-pc --recheck --no-floppy /dev/sda
mkdir -p /boot/grub/locale
cp /usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /boot/grub/locale/en.mo
vim /etc/default/grub
    GRUB_CMDLINE_LINUX="cryptdevice=/dev/sda3:root" # Mounts unecrypted sda3 to /dev/mapper/root.
    GRUB_DISABLE_LINUX_UUID=true
grub-mkconfig -o /boot/grub/grub.cfg

# finish
adduser
whef \n \n \n \n \n \n
usermod -p "" whef
passwd root
    *****
visudo
    Defaults targetpw # Must enter the password of the user you're running the command as.
    ALL ALL=(ALL) ALL # All users can use sudo.
exit
umount /mnt/{boot,}
reboot

Thanks a lot for your help! I hope I wasn't so verbose that I scared anyone off.

Whef

Member

Registered: 2012-08-26

Posts: 33

Re: UX31A BIOS boot?

To answer my own question, yes. It seems the UX31A motherboard doesn't have BIOS backwards compatibility. At any rate, I got UEFI working (took me, literally, two days). I faced a ton of challenges and errors, none of which were documented anywhere, but I don't think any of them are relevant to the UX31A as a whole.

Nebucatnetzer

Member

Registered: 2013-12-25

Posts: 6

Re: UX31A BIOS boot?

I'm sorry to rape this thread but this is an excellent guide on how to encrypt a laptop with an UEFI setup.
Much less confusing than the wiki.