Why bind to LiveCD /proc before building initramfs ? Post: 303001642

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Top Forums UNIX for Beginners Questions & Answers Why bind to LiveCD /proc before building initramfs ? Post 303001642 by Corona688 on Tuesday 8th of August 2017 11:29:22 AM

08-08-2017

Registered User

Quote:

Originally Posted by sreyan32

Imagine I have an unbootable system where I need to update the kernel image using

Code:

update-initramfs

.

I have seen numerous examples online which show the following

Code:

$ mount -t proc none /mnt/ubuntu/proc
$ mount -o bind /dev /mnt/ubuntu/dev
$ mount -o bind /sys /mnt/ubuntu/sys

After that we chroot into the broken OS and then execute the command to update the initramfs.

My questions are as follows-:
[LIST=1][*]Are we binding the /proc and /dev of the Live CD to the broken system ? Or are we binding the /proc and /dev of the broken system to the live cd ?

Neither. /dev and especially /proc are virtual filesystems, which don't show files but rather imaginary kernel things.

So they're neither livecd, nor your broken system, but something belonging to whatever kernel you're running.

These kernel / device interfaces are pretty hard for a system to do without.

Quote:

If building the initramfs is dependent on the information of the OS for which the initramfs is built then won't it contain erroneous information if we build for the Live CD ? That is use the /proc and /dev of the LiveCD ?

It doesn't so much archive them as use them.

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mkinitrd

MKINITRD(8)							      dracut							       MKINITRD(8)

NAME

       mkinitrd - is a compat wrapper, which calls dracut to generate an initramfs

SYNOPSIS

       mkinitrd [OPTION...] [<initrd-image>] <kernel-version>

DESCRIPTION

       mkinitrd creates an initramfs image <initrd-image> for the kernel with version <kernel-version> by calling "dracut".

	   Important
	   If a more fine grained control over the resulting image is needed, "dracut" should be called directly.

OPTIONS

       --version
	   print info about the version

       -v, --verbose
	   increase verbosity level

       -f, --force
	   overwrite existing initramfs file.

       *--image-version
	   append the kernel version to the target image <initrd-image>-<kernel-version>.

       --with=<module>
	   add the kernel module <module> to the initramfs.

       --preload=<module>
	   preload the kernel module <module> in the initramfs before any other kernel modules are loaded. This can be used to ensure a certain
	   device naming, which should in theory be avoided and the use of symbolic links in /dev is encouraged.

       --nocompress
	   do not compress the resulting image.

       --help
	   print a help message and exit.

AVAILABILITY

       The mkinitrd command is part of the dracut package and is available from https://dracut.wiki.kernel.org

AUTHORS

       Harald Hoyer

SEE ALSO

       dracut(8)

dracut								    06/12/2014							       MKINITRD(8)