How can I boot from a root filesystem (maybe squashfs or dd image)?

[MultimediaMan]

A Read Only NFSroots install is nearly perfect for what you want.

With a little juggling, it is possible to go with a Stateless (RO) NFSroots installation.

I have quite a bit of current production experience with Stateful (RW) NFSroots installations: they are actually quite stable; both PCBIOS and EFI (without SecureBoot).

RedHat and CentOS based installations are fairly portable to NFS (care must be taken to use some workarounds with somewhat intentionally-broken NFS boot support) in vmlinuz and initrd builds, but they ARE able to be worked-around with a fair amount of ease. The Workarounds involve installing kernel-devel, replacing the OEM vmlinuz kernel and initrd from the netinstaller or pxe vmlinuz/initrd out of the Installer ISO. Then preparations for NFS migration can continue with subsequent Kernel updates and initrd (dracut) rebuilds then able to take the NFS parameters correctly.

Ubuntu is fairly straightforward for NFSroots, again having to export the OS over to an NFS mount.

SuSE and Open SuSE are some of the few distributions that actually natively support an NFSroots installation; they are not perfect, but they certainly work.

I have a "Garage" computer that I triple boot (iSCSI for Windows, NFSroots for CentOS or Ubuntu) with iPXE and it's been running for three+ years on both OS with nary a hiccup.

Best,

M^3