Imagine I have an unbootable system where I need to update the kernel image using
.
I have seen numerous examples online which show the following
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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What's the correct way to change the initramfs file that's used during boot?
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Discussion started by: Azrael
0 Replies
LEARN ABOUT LINUX
pivot_root
PIVOT_ROOT(8) Maintenance Commands PIVOT_ROOT(8)NAME
pivot_root - change the root file system
SYNOPSIS
pivot_root new_root put_old
DESCRIPTION
pivot_root moves the root file system of the current process to the directory put_old and makes new_root the new root file system. Since
pivot_root(8) simply calls pivot_root(2), we refer to the man page of the latter for further details.
Note that, depending on the implementation of pivot_root, root and cwd of the caller may or may not change. The following is a sequence for
invoking pivot_root that works in either case, assuming that pivot_root and chroot are in the current PATH:
cd new_root
pivot_root . put_old
exec chroot . command
Note that chroot must be available under the old root and under the new root, because pivot_root may or may not have implicitly changed the
root directory of the shell.
Note that exec chroot changes the running executable, which is necessary if the old root directory should be unmounted afterwards. Also
note that standard input, output, and error may still point to a device on the old root file system, keeping it busy. They can easily be
changed when invoking chroot (see below; note the absence of leading slashes to make it work whether pivot_root has changed the shell's
root or not).
EXAMPLES
Change the root file system to /dev/hda1 from an interactive shell:
mount /dev/hda1 /new-root
cd /new-root
pivot_root . old-root
exec chroot . sh <dev/console >dev/console 2>&1
umount /old-root
Mount the new root file system over NFS from 10.0.0.1:/my_root and run init:
ifconfig lo 127.0.0.1 up # for portmap
# configure Ethernet or such
portmap # for lockd (implicitly started by mount)
mount -o ro 10.0.0.1:/my_root /mnt
killall portmap # portmap keeps old root busy
cd /mnt
pivot_root . old_root
exec chroot . sh -c 'umount /old_root; exec /sbin/init'
<dev/console >dev/console 2>&1
SEE ALSO chroot(1), mount(8), pivot_root(2), umount(8)AVAILABILITY
The pivot_root command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
Linux Feb 23, 2000 PIVOT_ROOT(8)