FSIyagi — One Partition for Windows and Linux (Delete-Protection Filesystem)

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Windows and Linux read and write the same partition. FSIyagi is a partition format that takes the place of NTFS, ext4, or exFAT. On a dual-boot PC both systems see the same original folders, so there is no more "which side has the latest copy?"

	NTFS	ext4	exFAT	FSIyagi
Read/write on Linux	△ (ntfs3 · ntfs-3g)	✔	✔	✔
Read/write on Windows	✔	✘	✔	✔ (own driver, drive letter)
Journaling (power-loss safety)	✔	✔	✘	✔
Delete protection	✘	✘	✘	✔

And the partition keeps project folders from being deleted — by accident, or by a runaway script. Reads, writes, and creation all pass through untouched. Only deletion is refused.

os.remove()  shutil.rmtree()  find -delete  rm  perl unlink
                          │
                          ▼  they all collapse into the same syscall
                    unlink / rmdir
                          │
                    FSIyagi  ──▶  refused (EPERM)

No matter which language or tool tries to delete, it passes through the same point in the kernel, so blocking it there leaves no way around it. This isn't a command-name check, so a script that imitates rm or calls it under a different name is blocked just the same.

It also guards against wiping a file's contents without deleting it (> file.cpp, a mistaken save in an editor, and so on) by keeping one copy of a file's contents from just before it gets overwritten (the Vault).

Install

Linux

⬇ Latest release

Your system	File to pick
Ubuntu 24.04 · Debian	.deb marked ubuntu24.04
Ubuntu 26.04	.deb marked ubuntu26.04
Fedora · openSUSE	.rpm
Arch · Manjaro	.pkg.tar.zst
Any other Linux	.AppImage or .zip

sudo apt install ./fsiyagi_*_amd64.deb       # Ubuntu / Debian

Nothing turns on automatically after install. Choosing the mount point yourself is the point, so the service is started manually too.

Windows

The Windows version is coming to Releases. The installer adds the FSIyagi driver; then assign a drive letter to the FSIyagi partition in fsiyagi-manager: it shows up in Explorer like any NTFS drive, and since Windows remembers the letter, it mounts on its own at every boot.

On Windows, the right to delete belongs to the local group "FSIyagi Guard" instead of Linux's fsguard group. The installer creates that group and adds the user who is signed in. Windows can open partitions formatted in NATIVE MODE (see "Two storage modes" below).

First use

1. Add your account to the group allowed to delete

Only processes in the fsguard group may delete. Everyone else — including an admin account — has every delete attempt refused.

sudo gpasswd -a "$USER" fsguard

Log in again for this to take effect.

2. Prepare a partition with the management UI

fsiyagi-manager

Pick a partition from the disk list, then Format and Mount it. For a first try, start with an empty or disposable partition rather than one you already rely on.

3. Use it as normal

Inside the mounted directory, creating, editing, and building files all work exactly as they always have. The one difference: trying to delete is refused.

$ rm important.txt
rm: cannot remove 'important.txt': Operation not permitted

When you genuinely need to delete something, borrow fsguard group privileges explicitly through fsiyagi-admin:

fsiyagi-admin run rm important.txt

4. Check on things through the UI

The Disks tab in fsiyagi-manager shows usage and mount state. The Tools tab lets you find and restore preserved originals from the Vault, inspect the policy, or undo a format if needed.

Two storage modes

	EXT4 MODE	NATIVE MODE
Storage format	Layered on standard ext4	Own on-disk format
Recovery	Works with ordinary ext4 tools	Needs the dedicated fsck
Best for	Compatibility, existing setups	Performance, self-containment
Opens on Windows	✘	✔

You choose which mode to use at mount time. Both modes share the same delete-protection code, so the behavior is identical either way.

Language

The UI follows your system language automatically. Supported: Korean, English, Deutsch, Español, Français, Bahasa Indonesia, 日本語, Português, Русский, Türkçe, Tiếng Việt, 中文. To force a specific language, add ui/language=<code> to the config file (e.g. ko, ja).

Troubleshooting

Deletion fails with Operation not permitted That's the intended behavior. Run it through fsiyagi-admin run <command>, or check that your account is in the fsguard group (groups).

The mount point shows up empty If the mount point already had content but the target partition is empty, mounting is refused outright to prevent that content from silently disappearing under a blank overlay. Double-check you picked the right partition in fsiyagi-manager.

Transport endpoint is not connected The daemon died. Unmount and mount again.

I want to undo a format If you enabled the "save a backup for undo" option when formatting, you can undo it from the Tools tab in fsiyagi-manager. The data area is never touched by formatting, so as long as nothing new has been written to the partition since, the original filesystem comes back intact.