[generator] Add warning if boot without initramfs is possible.

[oech3]

linux 6.14.arch1-1 of Arch Linux is built with CONFIG_BTRFS_FS=y and CONFIG_SATA_AHCI=y.

In such case, booster generate initramfs without any modules if modules are highly selected in config. User can move to initramfs less setting if warning about it appear.

By the way, rootflags=noatime without initramfs is impossible (https://bugzilla.kernel.org/show_bug.cgi?id=61601 ). Surprisingly, lz4 compressed moduleless booster initramfs is FASTER than no initramfs+a service to remount / with noatime. Moreover, systemd-gpt-auto-generator does not work with Btrfs / (https://github.com/systemd/systemd/issues/16953). Thus, booster is still useful. It may be a motivation to make small init binary.

Edit: fixed to correct url.

[anatol]

Thank you, this is indeed might be a useful warning for the boot speed improvement enthusiasts.

I am trying to figure out what would be the criteria for the initrd-less boot. Basically booster modifies the system in multiple ways:

• loads kernel modules based on the available hardware
• uses boot flags to perform the required actions
• uses booster config to perform the required actions (e.g. configures network needed for boot)

Further looking into the configuration options currently available - all of them affect the boot process itself, but are not intended to alter the booted machine state.

So it really the modules and boot flags that booster uses to alter the machine. If there is a clean criteria to detect situation of no-op initrd then we can add a warning for it.