Dual-Boot
The installer can install into existing free space instead of wiping the disk, but it never shrinks anything for you.
The installer supports installing into free space on a disk that already has another OS on it (Windows, most commonly), rather than wiping the whole disk. It does not shrink an existing partition for you: you free up the space yourself first, the same way you would for any other dual-boot install.
1. Free up space
From Windows: Disk Management → right-click the partition to shrink → Shrink Volume → enter how much space to free up. This becomes the disk's unallocated space that sobarch installs into. Leave at least 20GiB free; less than that isn't enough for a comfortable install.
2. Install into the free space
On the disk-selection screen, a disk with enough free space on it (UEFI only; see below) offers a second option alongside the usual "wipe entire disk" one: installing into that free space instead. Picking it:
- Leaves every existing partition on the disk untouched.
- Reuses the disk's existing EFI System Partition (ESP) if it has one, rather than creating a second one -- the same ESP Windows' own bootloader already lives on ends up shared with sobarch's.
- Disables rescue media for this install (the extra partitions it needs aren't worth the added complexity on a disk already shared with another OS).
This is UEFI/GPT only. A BIOS/MBR disk never offers this option: MBR's 3-primary-partition limit is already tight for sobarch's own layout (see Rescue Media), and dual-boot with an existing OS is overwhelmingly a UEFI scenario anyway.
3. Add the other OS to the boot menu
Limine has no built-in equivalent to GRUB's os-prober, so after your first boot into sobarch, open a terminal and run:
sudo /usr/local/lib/sobarch/limine-add-os-entry.shIt lists the other bootloader(s) it finds on the shared ESP, asks which one to add and what to call it, and writes the entry into Limine's boot menu. Run it again for additional OSes, or to pick a different entry.
This approach (install into pre-existing free space, leave shrinking to the user, add the other OS to the boot menu as a manual post-install step) follows the same shape Omarchy's own dual-boot support takes.