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linux/Documentation/ABI/testing/sysfs-firmware-initrd

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initramfs: Expose retained initrd as sysfs file When the kernel command line option "retain_initrd" is set, we do not free the initrd memory. However, we also don't expose it to anyone for consumption. That leaves us in a weird situation where the only user of this feature is ppc64 and arm64 specific kexec tooling. To make it more generally useful, this patch adds a kobject to the firmware object that contains the initrd context when "retain_initrd" is set. That way, we can access the initrd any time after boot from user space and for example hand it into kexec as --initrd parameter if we want to reboot the same initrd. Or inspect it directly locally. With this patch applied, there is a new /sys/firmware/initrd file when the kernel was booted with an initrd and "retain_initrd" command line option is set. Signed-off-by: Alexander Graf <graf@amazon.com> Tested-by: Bagas Sanjaya <bagasdotme@gmail.com> Link: https://lore.kernel.org/r/20231207235654.16622-1-graf@amazon.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-12-07 16:56:54 -07:00
What: /sys/firmware/initrd
Date: December 2023
Contact: Alexander Graf <graf@amazon.com>
Description:
When the kernel was booted with an initrd and the
"retain_initrd" option is set on the kernel command
line, /sys/firmware/initrd contains the contents of the
initrd that the kernel was booted with.
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