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initrd in desktop

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Ciro Santilli
2018-02-16 09:39:13 +00:00
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@@ -1526,12 +1526,26 @@ The main ingredients to get this working are:
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It is also possible to compress that image with other options. It is also possible to compress that image with other options.
* `qemu -initrd`: make QEMU put the image into memory and tell the kernel about it. * `qemu -initrd`: make QEMU put the image into memory and tell the kernel about it.
* `CONFIG_BLK_DEV_INITRD=y`: Compile the kernel with initrd support * `CONFIG_BLK_DEV_INITRD=y`: Compile the kernel with initrd support, see also: https://unix.stackexchange.com/questions/67462/linux-kernel-is-not-finding-the-initrd-correctly/424496#424496
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Buildroot forces that option when `BR2_TARGET_ROOTFS_CPIO=y` is given Buildroot forces that option when `BR2_TARGET_ROOTFS_CPIO=y` is given
https://unix.stackexchange.com/questions/89923/how-does-linux-load-the-initrd-image asks how the mechanism works in more detail. https://unix.stackexchange.com/questions/89923/how-does-linux-load-the-initrd-image asks how the mechanism works in more detail.
==== initrd in desktop distros
Most modern desktop distributions have an initrd in their root disk to do early setup.
The rationale for this is described at: https://en.wikipedia.org/wiki/Initial_ramdisk
One obvious use case is having an encrypted root filesystem: you keep the initrd in an unencrypted partition, and then setup decryption from there.
I think GRUB then knows read common disk formats, and then loads that initrd to memory with a `/boot/grub/grub.cfg` directive of type:
initrd /initrd.img-4.4.0-108-generic
Related: https://stackoverflow.com/questions/6405083/initrd-and-booting-the-linux-kernel
==== initramfs ==== initramfs
initramfs is just like initrd, but you also glue the image directly to the kernel image itself. initramfs is just like initrd, but you also glue the image directly to the kernel image itself.