[ahepp]

If you're familiar with the Linux boot process, you may be aware that the system often does run from RAM for a period of time, before mounting a filesystem from a block device and calling pivot_root to transfer the rootfs over.

If you want to run the OS from RAM, the absolute simplest way to do it is to simply never transfer. Building a custom initramfs has never been easier. There are tools explicitly geared towards making an initramfs, like Dracut, but also a huge ecosystem of tools for building container images which could almost certainly be scripted to spit out a cpio without a lot of trouble. You can even use something like Buildroot.

As far as loading it from the network easily, I would also look into Unified Kernel Images (UKIs). They combine the EFI stub, the kernel, and the initramfs into one single file. You should be able to load that directly from the PXE firmware.

[hardwaresofton]

Yeah I'm famliar with initramfs-es (well at least enough to be dangerous)! I've run Alpine from ram before but it just wasn't stable and I ended up going back to a more traditional and perfectly fine setup.

> If you want to run the OS from RAM, the absolute simplest way to do it is to simply never transfer. Building a custom initramfs has never been easier. There are tools explicitly geared towards making an initramfs, like Dracut, but also a huge ecosystem of tools for building container images which could almost certainly be scripted to spit out a cpio without a lot of trouble. You can even use something like Buildroot.

This certainly seems like a lot of responsibility to take on, I'm just surprised there isn't already a distro that is very good at doing everything it does (with modern ease of use) with the caveat of the OS disk being in RAM. Technically there are (there's a whole list on Wikipedia), but last I tried it just didn't work well for me.

These days there are more build-your-own distro options like CoreOS, Flatcar, linuxkit that absolutely make things even easier but they don't have that final bit of being runnable from RAM.

I question whether it's worth it to maintain my own UEFI/initramfs/boot setup rather than just building (or pulling off the shelf) an immutable OS image and using the reset + wipe automation to flash the disks once in a blue-moon when reconfiguring/scaling machines up/down.

> As far as loading it from the network easily, I would also look into Unified Kernel Images (UKIs). They combine the EFI stub, the kernel, and the initramfs into one single file. You should be able to load that directly from the PXE firmware.

This is certainly interesting -- haven't looked into these much, but this would certainly be useful in the PXE firmware (or custom UEFI). But my problem here is that iPXE is dependent on support at the provider level (and Hetzner does not make this available to end users, though they use it internally obviously when you reset), so the other commenter's suggestion:

> replace the PXE stack with an OS installer written in UEFI.

Would not work with this approach. The suggestion is interesting though, custom installer that pulls down a UKI sounds viable from my particular armchair.

[wazdra]

Tails works like this, and has gained a lot of traction in the past few years — although one may argue that running from RAM is only indirectly responsible for its popularity.

I think this idea appeals to many people, also concerning remanence: keeping your system and user data separate to the point that you could virtually mount your /home on any given UNIX host, with the added bonus that if the host is not compatible with your setup, you can always reboot it on your USB stick, run a live ISO on RAM, and retrieve a decent work environment.