Depending on the scrap collected - you may not be able to use Legacy boot.
I have an 5y old Acer winbook - no legacy boot
I have a 3y old Yepo winbook - no legacy boot
Using xfce iso minimal (codename Ruah)
- fresh download of manjaro-xfce-21.3.7-220816-linux515.iso
My test subject is a 8y old Asus laptop with an 240G ssd booted in efi mode and installed in efi mode.
CSM enabled.
- → Reboot to a ventoy disk using boot override
- → choice between efi and bios
- → select bios (the non efi entry)
- → select xfce minimal (codename Ruah)
- → added a 240G SSD on usb (empty no partitions)
- → started installer
- → select usb (/dev/sdc)
- → select erase disk (swap - no hibernate - ext4)
- → installer creates dos partition set
- → installer fails on bootloader
→ caused by my mistake - I didn’t check which device to install the loader on
→ preselected to /dev/sda
→ fail is to be expected - you cannot write mbr to a gpt disk
Reboot test subject
repeat step 1…8
- → set bootloader to /dev/sdc
- → installer creates parition set
- → installer finish with no errors
Rebooted and sucessfully booted from USB on bios/mbr
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS
sda 8:0 0 223,6G 0 disk
├─sda1 8:1 0 300M 0 part
├─sda2 8:2 0 214,5G 0 part
└─sda3 8:3 0 8,8G 0 part
sdb 8:16 0 476,9G 0 disk
├─sdb1 8:17 0 76,9G 0 part
├─sdb2 8:18 0 32M 0 part
└─sdb3 8:19 0 400G 0 part
sdc 8:32 0 223,6G 0 disk
├─sdc1 8:33 0 214,8G 0 part /
└─sdc2 8:34 0 8,8G 0 part [SWAP]
sr0 11:0 1 1024M 0 rom
$ sudo fdisk -l /dev/sda
Disk /dev/sda: 223,57 GiB, 240057409536 bytes, 468862128 sectors
Disk model: OCZ-AGILITY3
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 1CC09109-A435-6A43-BFD0-7CE414902324
Device Start End Sectors Size Type
/dev/sda1 4096 618495 614400 300M EFI System
/dev/sda2 618496 450402086 449783591 214,5G Linux filesystem
/dev/sda3 450402087 468857024 18454938 8,8G Linux swap
$ sudo fdisk -l /dev/sdc
Disk /dev/sdc: 223,57 GiB, 240057409536 bytes, 468862128 sectors
Disk model: ITY3
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xd5abf184
Device Boot Start End Sectors Size Id Type
/dev/sdc1 * 2048 450402086 450400039 214,8G 83 Linux
/dev/sdc2 450402087 468857024 18454938 8,8G 82 Linux swap / Solaris
In theory it is possible to boot both bios and efi from same disk - condition - you use grub.
Create an unformatted partition of size between 1M-32M (calamares prefer 32M) on a GPT disk with partition type EF02.
Then run grub-install for i386 targeting the device
It is possible to migrate to Arch32 - I haven’t done it lately so the notes may be imcomplete