Hop – Install Linux next to Windows without a USB stick

The idea

A USB installer is a FAT32 drive with the ISO's files on it, which the PC's firmware starts. hop makes the same thing on the internal disk: a small FAT32 partition, plus a one-time startup entry.

Before [EFI][MSR][ C: Windows ][Recovery] After [EFI][MSR][ C: Windows ][ Installer ][ Linux ][Recovery]

The installer sits straight after C:, so once Linux is installed, removing it hands its space to C:. Undo extends C: over all of it. Older builds put the installer after Linux, where Windows can't reach it.

src/ (C#, WinForms on .NET Framework 4.8) The window, plus what PowerShell can't do well: UEFI variables (Firmware.cs) and raw disk reads (DiskProbe.cs)

engine/ (Windows PowerShell 5.1) Everything that happens to the PC. Embedded in the exe and run in-process, because the Storage cmdlets are the supported way to resize partitions

Both ship with Windows 10 and 11, so hop.exe needs nothing installed. Engine.cs hosts the scripts in a runspace and calls their functions one at a time. Progress comes back through a shared hashtable, $Sync, which the window polls.

File What it does

Common.ps1 Names and labels, logging and progress. Loaded first

System.ps1 Blockers and warnings, BitLocker and Fast Startup

Catalog.ps1 The list of systems

Download.ps1 Finds the official ISO, downloads and verifies it

Iso.ps1 Mounts an ISO and checks hop can use it

SecureBoot.ps1 Works out whether Secure Boot will let the ISO start

Disk.ps1 Plans the space, makes partitions, copies files

Boot.ps1 The EFI partition and the startup entry

State.ps1 What hop left on this PC, and state.json

OtherLinux.ps1 Finds and removes another Linux, such as Pond

Install.ps1 The main flows: install, restart and undo

Steps.ps1 What to click in each Linux installer

Report.ps1 The bug report

The install, step by step

Check the PC (Get-Blockers).

Download and verify, or take the user's ISO.

Mount and check the ISO, check Secure Boot will start it and the EFI partition has room, and plan the space. Nothing on the disk has changed yet.

Save the state, pause BitLocker, turn off Fast Startup.

Shrink C: if needed, and make the partitions. Each is recorded before it's formatted.

Copy the files and compare them one by one, then mark Copied.

Add the startup entry. A failure here is kept, not rolled back, and Restart now tries again.

On Restart now, and not before, set the one-time start. Other restarts still go to Windows.

A failure in steps 4 to 6 runs Invoke-Cleanup, which puts everything back.

What Where How it's found

Installer partition After Linux Label HOPINSTALL

Linux partitions (prepared systems) After C: Labels LINUXBOOT, LINUXROOT

Boot loader copy \EFI\hop on the EFI partition Fixed path

Startup entry UEFI variables (hop) in its name

State and logs C:\ProgramData\hop Fixed path

Clean-up works from these, not just the state file, so it works after a crash. Builds named LinuxHop used LINUXHOP, \EFI\linuxhop and (LinuxHop), which are still recognised.

Read from the boot files of the ISOs in the catalog (October 2026):

A problem from step 3 onwards stops at GRUB or the Linux console. Coming straight back to Windows means step 1 or 2 failed, or the firmware never tried: firmware moves on to the next startup entry when a loader is refused or exits. Firmware clears BootNext as it starts, so one still set after coming back means it never tried, which is what Test-BootNextIgnored looks for.

bcdedit can only make Windows Boot Manager objects, and the firmware's one-time boot can't use those. Firmware.cs writes Boot#### and BootNext itself, as efibootmgr does on Linux.

To Windows, an ext4 partition and a locked BitLocker drive look the same: unreadable, with no letter. DiskProbe.cs reads the first bytes of the partition, so hop only offers to remove what it can positively identify as Linux.