chapter: role of the initramfs

[orangecms]

probably under LinuxBoot Components

TL;DR Linux needs a rootfs; either storage/partition with any supported fs, or initrd, or initramfs

initrd is being deprecated (has been for a decade anyway...):
https://www.phoronix.com/news/Initrd-Linux-Try-Removing-2025
because it is treated as a block device, which causes overhead

initramfs just means it's a cpio, can be either included in the kernel (CONFIG_INITRAMFS_SOURCE, mind calling it *.cpio or, if compressed. *.cpio.xz etc) or passed by placing in memory and giving the address via cmdline.
initrd can also be passed via cmdline, and the distinction is made by Linux when it recognizes a cpio - then it's an initramfs.

cmdline argument: initrdmem https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html

• https://docs.kernel.org/filesystems/ramfs-rootfs-initramfs.html
• https://www.kernel.org/doc/Documentation/blockdev/ramdisk.txt
• https://www.kernel.org/doc/html/latest/admin-guide/initrd.html

[rminnich]

might want to comment that it can be one or more cpio concatenated together, and if a file is seen twice, the most recent version wins.