2 clarify some details
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If you have an initramfs the kernel just unpacks and mounts the initramfs and executes /init, nothing afterwards. Everything else will happenbe handled by the /init executable. This also means the kernel doesn't mount the device specified in the root boot parameter.

Different Distributions use different initramfs frameworks like e.g. dracut for Fedora or initramfs-tools for Debian. Most common solutions are either using something like udev, mdev or devtmpfs. Some may also just use MAKEDEV to generate a static layout or have the device files already integrated into their image.

If you boot without an initramfs the kernel can just boot from devices with known major/minor numbers, e.g. /dev/sda1 but not from lvm devices.

If you have an initramfs the kernel just mounts and executes /init, nothing else will happen. This also means the kernel doesn't mount the device specified in the root boot parameter.

Different Distributions use different initramfs frameworks like e.g. dracut for Fedora or initramfs-tools for Debian. Most common solutions are either using something like udev, mdev or devtmpfs. Some may also just use MAKEDEV to generate a static layout or have the device files already integrated into their image.

If you boot without an initramfs the kernel can just boot from devices with known major/minor numbers, e.g. /dev/sda1 but not from lvm devices.

If you have an initramfs the kernel just unpacks and mounts the initramfs and executes /init afterwards. Everything else will be handled by the /init executable. This also means the kernel doesn't mount the device specified in the root boot parameter.

Different Distributions use different initramfs frameworks like e.g. dracut for Fedora or initramfs-tools for Debian. Most common solutions are either using something like udev, mdev or devtmpfs. Some may also just use MAKEDEV to generate a static layout or have the device files already integrated into their image.

If you boot without an initramfs the kernel can just boot from devices with known major/minor numbers, e.g. /dev/sda1 but not from lvm devices.

1
source | link

If you have an initramfs the kernel just mounts and executes /init, nothing else will happen. This also means the kernel doesn't mount the device specified in the root boot parameter.

Different Distributions use different initramfs frameworks like e.g. dracut for Fedora or initramfs-tools for Debian. Most common solutions are either using something like udev, mdev or devtmpfs. Some may also just use MAKEDEV to generate a static layout or have the device files already integrated into their image.

If you boot without an initramfs the kernel can just boot from devices with known major/minor numbers, e.g. /dev/sda1 but not from lvm devices.