The one thing that trips people up: Ryoku does not shrink Windows for you.
If Windows fills the whole disk, there is no free space for Ryoku, and the
installer’s Disk layout step will not let you continue (Tab does nothing)
until you free some space. Do Step 1 first.
What you need
Dual-boot alongside Windows requires all of these:- UEFI + GPT. Boot the Ryoku USB in UEFI mode (not BIOS/CSM/legacy). A UEFI Windows install already uses GPT and has an EFI System Partition (ESP).
- An existing EFI partition to reuse — a UEFI Windows install has one.
- Enough unallocated free space for Ryoku: at least 15 GiB for the root plus your swap size (the default swap is 16 GiB, so ~31 GiB; 64 GiB or more is comfortable). Ryoku and the Windows boot manager then share the one ESP.
Step 1: Make room in Windows
Do this from Windows, before booting the installer.1
Turn off Fast Startup and BitLocker
Fast Startup leaves the Windows filesystem in a hibernated state, which can
corrupt data when another OS touches the disk. Turn it off: Control Panel →
Power Options → Choose what the power buttons do → uncheck “Turn on fast
startup”. If BitLocker is on, suspend or disable it first (and save your
recovery key).
2
Shrink the Windows partition
Press
Win + X → Disk Management. Right-click your Windows (C:) volume →
Shrink Volume, and shrink it by at least the space Ryoku needs (aim for
64000 MB / 64 GiB or more). This leaves Unallocated space after the
Windows partition — that is where Ryoku goes.3
Fully shut down Windows
Use Shut down (not Restart, not Sleep) so the disk is left clean.
Step 2: Disable Secure Boot
Reboot into your firmware setup (usuallyF2, Del, or F12 at power-on) and
turn Secure Boot off. Save and exit. See Install Ryoku for
the full pre-install checklist and how to write the USB.
Step 3: Install alongside Windows
Boot the Ryoku USB in UEFI mode. In the installer:1
Pick the target disk
At Target disk, choose the disk that holds Windows.
2
Choose the alongside strategy
At Disk strategy, pick Install alongside Windows (it is the first,
default option). Nothing is written until the final Review step.
3
Confirm the layout, then press Tab
The Disk layout step shows your disk: the kept Windows and EFI
partitions, and a new Ryoku root in the free space. Adjust swap if you like,
then press Tab to continue to Review. Confirm on Review to install.
”I press Tab and nothing happens”
On the Disk layout step, Tab only continues once the alongside layout is actually installable. When it is blocked, the screen shows a red⚠ line with
the reason. The usual causes:
Not enough free space (the most common one)
Not enough free space (the most common one)
Windows is using the whole disk, so there is no room for Ryoku. Go back to
Step 1 and shrink the Windows partition to
leave at least 15 GiB plus your swap size of unallocated space, then reboot
into the installer. (Or press
esc and choose Erase whole disk on a
dedicated drive.)No EFI partition to reuse
No EFI partition to reuse
The installer found no EFI System Partition on the disk. This happens when
Windows was installed in legacy/BIOS (MBR) mode instead of UEFI, or when
you booted the USB in BIOS mode. Reinstall/boot in UEFI mode, or press
esc
and choose Erase whole disk.The disk is smaller than 32 GiB
The disk is smaller than 32 GiB
Ryoku needs at least 32 GiB total. Pick a larger disk.
After install
The Limine boot menu appears at power-on with entries for Ryoku and Windows — pick whichever you want. If Windows does not appear, boot Ryoku and runryoku doctor, then see Troubleshoot.
See also
Install Ryoku
The full install walkthrough, from ISO to first boot.
Troubleshoot
Boot, login, and disk recovery when something goes wrong.