Meet Luft

How Meet Luft prepares a Windows or Linux computer for Luft, makes USB sticks and keeps logs from Try Luft. The app is in apps/meet.

Which Luft it downloads

Meet Luft only downloads the image the computer needs: luft-latest-nvidia.iso when it has an NVIDIA graphics card, hybrid laptops included, and luft-latest-standard.iso otherwise (luft-nightly-… for nightly builds), each with its .sha256. Until a build has its own image for that, it falls back to the universal luft-latest.iso. The size it shows is the real size of that download, and Get the newest Luft keeps to the same one.

On Windows

The steps people see are in Try Luft with Meet Luft. Underneath:

• Windows shrinks its own partition through its storage service, as Disk Management does, so it works with BitLocker on. Luft’s room and Meet Luft’s partitions go right after Windows, in front of a recovery partition at the end of the drive.
• The download is checked against its .sha256, and the live system is copied out of the ISO as it arrives.
• The start entry Meet Luft goes at the end of the firmware’s list, and the firmware is asked to use it once (BootNext). Some firmware drops entries it doesn’t know, so Meet Luft puts it back before each restart. Luft starts through Fedora’s signed shim and GRUB, like the stick.
• The clock (RealTimeIsUniversal) and Fast Startup are changed in Windows itself, so they work with BitLocker on, where Luft can’t read Windows’ drive.
• The moving box holds folders from the Windows account, the wallpaper, name and account picture, time zone, keyboard and language, Bluetooth pairings, and Wi-Fi networks with their passwords when ticked.

Partitions

Partition	Size	What’s on it
Luft’s room	your choice, at least 32 GB (34 GB next to a small EFI system partition)	Empty until Luft is installed into it
Moving box	what you packed, plus a little	exFAT, labelled Moving box, with box.json listing what’s inside
Start	about 512 MB	FAT, an EFI system partition of its own with shim, GRUB, the kernel and its initramfs
Luft	the live system plus 1 GB	exFAT, labelled Luft, with LiveOS from the ISO, meet.json and the logs from Try Luft

When Windows encrypts new partitions with BitLocker as soon as they’re formatted, as it does on PCs with device encryption, Meet Luft decrypts its own right away, so the firmware and Luft can read them. Windows’ drive stays encrypted. Meet Luft also notes the partitions it made in C:\ProgramData\Lantharos\Meet Luft\made.json, so it can always take them back out.

meet.json names Meet Luft’s partitions by their GUIDs, the room, the start entry and whether the last restart was to try or to install. The live system finds its partition with root=luft-live:PARTUUID=… on the kernel command line; the stick uses root=luft-live:LABEL=…. None of the partitions get a drive letter.

After Luft is installed and you sign in for the first time, it removes the start entry, the moving box, the start and live partitions, and grows into the space they used.

Getting a newer Luft

When a newer Luft is out than the one on its partition, Meet Luft offers Get the newest Luft next to Try Luft. Newer means a different checksum than the build it copied, from the releases or nightly builds Meet Luft is using, or from an ISO picked with Use an ISO I already have; an ISO without a .sha256 next to it always counts as newer. It downloads the new build in place of the old one and keeps the room, the moving box and the logs from Try Luft. When the new build fits the partitions Meet Luft already made, only their files change. Otherwise it makes them again at the size the new build needs, taking what’s missing from Windows, and adds the start entry back. Meet Luft remembers which build it copied by its checksum in LiveOS\iso.sha256. If an update stops halfway, Meet Luft won’t restart into Luft until the update is done.

Making a USB stick

Make a USB stick, on the first screen and next to Try Luft and Install Luft, puts Luft on a stick, on Windows and on Linux. It lists only USB drives that can be taken out, with each one’s name, size and what’s on it. Internal drives, read-only sticks, the drive the computer runs from and the drive holding a chosen ISO never show up. Sticks are looked for again every few seconds, so one plugged in later appears by itself.

By default the stick gets the universal image, luft-latest.iso (luft-nightly.iso for nightly builds), since a stick is often used on other computers. For this PC picks the smaller image built for this computer’s graphics instead, luft-latest-standard.iso or luft-latest-nvidia.iso. Use an ISO I already have writes that ISO, checked against a .sha256 next to it when there is one.

Downloads are checked against their .sha256 and kept, so the next stick doesn’t download again: in ~/.cache/luft-meet on Linux, and %LOCALAPPDATA%\Lantharos\Meet Luft\Downloads on Windows. A newer build replaces the one kept there. They can be deleted any time.

Erasing the stick

Meet Luft names the stick and asks before erasing it. It writes the ISO to the whole stick, reads everything back and compares its SHA-256 with the ISO’s, then ejects the stick.

• Windows: the helper locks and dismounts each of the stick’s volumes, clears its partition table and writes \\.\PhysicalDriveN unbuffered, as Rufus does. Windows then reads the new partitions, and the stick is ejected like Safely Remove Hardware does.
• Linux: the helper unmounts the stick’s partitions through UDisks, opens the drive exclusively with O_DIRECT, writes and flushes it, reads it back past the page cache, and powers it off through UDisks.

Ventoy

A stick made with Ventoy is recognised the way Ventoy recognises it: its first partition starts at 1 MiB, its second is exactly 32 MiB right after it and is the FAT partition labelled VTOYEFI (named VTOYEFI too on GPT). Meet Luft then asks whether to add Luft to it, or to erase the whole stick and make it a Luft stick.

Adding copies the ISO into Ventoy’s data partition, the large exFAT or NTFS one, next to the other ISOs. On Windows it’s opened by its drive letter or volume path; on Linux through UDisks when it isn’t mounted yet. Meet Luft checks the free space first, asks before replacing a Luft ISO already on the stick, copies to a temporary name, reads the copy back and compares its SHA-256, and only then gives it its name and ejects the stick.

Luft starts from Ventoy’s normal mode, with nothing to set in ventoy.json: Ventoy maps the ISO onto a device-mapper device, and Luft’s live system looks for its label on every block device, not only on whole sticks. With Secure Boot on, Ventoy asks once, on its own blue screen, to enroll its key.

Logs from Try Luft

When Luft starts from Meet Luft’s partition or folder, it keeps its logs on that partition, so problems on real hardware can be looked at from Windows afterwards. It saves them a minute after starting, every five minutes after that, right after an app crashes, and when it shuts down or restarts, so pulling the plug loses a few minutes at most. Each start gets one zip, Luft logs\YYYY-MM-DD HH-MM-SS.zip on the Luft partition (on Linux, in Meet Luft’s folder), named after the time of its first save, and each save replaces it whole. Starting from a USB stick saves nothing.

A zip stays under 48 MB. When the logs of one start get bigger than that, the JSON journal is left out first, then only the last part of the text journal is kept. The last five starts are kept, and older ones are removed sooner when the partition gets short of space.

File	What’s in it
journal.txt	The whole journal of that start (journalctl -b -o short-precise)
journal.json.zst	The same journal as JSON, compressed with zstd
kestrel.txt	Kestrel’s own messages: the desktop, setup mode, the login screen and the graphics watchdog
kestrel-watchdog	The graphics watchdog’s records, when it has any
coredumps.txt	coredumpctl list and coredumpctl info for every crash, with backtraces
dmesg.txt	Kernel messages
system.txt	Kernel, version, command line, meet.json, memory, free space and drives
lspci.txt, lsusb.txt	Devices and their drivers (lspci -nnk, lsusb, lsusb -t)
drm.txt	The framebuffer and logo the firmware left, graphics cards and their drivers, and each connector’s state and modes
vainfo.txt	Video decoding, for each render node
graphics.txt	Vulkan and EGL drivers and devices (vulkaninfo --summary, eglinfo -B)
sushi.txt	sushictl status
sabine	Sabine’s logs from the live account, with Chromium’s own log in chromium.log

In Meet Luft, Ctrl+Shift+L copies the newest zip to the desktop as Luft logs YYYY-MM-DD HH-MM-SS.zip, and Show opens it in Explorer or your file manager.

To read them without Meet Luft, use the partition’s volume path. It works without giving the partition a drive letter, and only reads:

$luft = (Get-Volume -FileSystemLabel Luft).Path        # \\?\Volume{…}\
Get-ChildItem -LiteralPath "${luft}Luft logs"
Copy-Item -LiteralPath "${luft}Luft logs" -Destination "$env:TEMP\Luft logs" -Recurse

Taking it back out

Remove Luft from this PC deletes the start entry and every partition Meet Luft made, moving box included, and gives Windows all of its space back. Once Luft is installed, its partition is Luft’s own: remove it from Windows’ Disk Management if you go back.

Running it

Meet Luft asks Windows for administrator rights once, when it first looks at the drive. A small helper does the disk and firmware work with those rights; the window itself runs as you, so it sees your own folders and settings. It needs Windows 10 or 11, and an internet connection unless you pick an ISO.

When a step doesn’t finish, Meet Luft says which one and offers to try it again. What went wrong is written to %LOCALAPPDATA%\Sabine\logs\meet.jsonl.

On Linux

Meet Luft for Linux is an AppImage. It needs UEFI and a GPT drive, and checks Secure Boot, the TPM, the graphics card (an NVIDIA card gets the image with NVIDIA’s driver), the Wi-Fi chip, free space, the EFI system partition and how the system is laid out.

Nothing is repartitioned. Meet Luft keeps the live system as files in a folder, /home/.luft-meet on the drive that holds your home folder, or /var/lib/luft-meet/live when that one can’t be used. The folder has to be on ext4, btrfs or XFS on a plain partition: Luft can’t start from an encrypted drive, LVM or RAID yet, and Meet Luft says so. Next to the system’s own boot files on the EFI system partition it adds EFI/luft-meet with Fedora’s signed shim and GRUB, about 5 MB, and a start entry called Meet Luft. GRUB reads the kernel and initramfs straight from the folder, and the live system finds it with root=luft-live:UUID=<file system>/<folder> on the kernel command line, the folder being its path from the top of the file system (for btrfs, from the top-level subvolume). Restarting sets BootNext once, so the restart after that is back in the old system.

Secure Boot can stay on: Luft starts through Fedora’s shim and GRUB, like the stick. Luft’s own key is only added when it’s installed, with the usual blue screen at its first start.

Luft is ready offers Try Luft, Replace and Install Luft; Try Luft with Meet Luft describes them.

Get the newest Luft and the nightly builds (Ctrl+Shift+N) work as on Windows. Remove Luft from this computer deletes the folder, EFI/luft-meet and the start entry. /var/lib/luft-meet/made.json notes what Meet Luft made, so it can always take it back out. After Luft is installed and you sign in for the first time, it removes them itself.

Meet Luft asks for your password through polkit once, when it first looks at the computer; a helper started with pkexec does the work on the drive and the firmware, and the window runs as you.