Query 1. If you remove initrd or
initramfs image or kernel from server what will happen?
Ans: If you remove initrd or
initramfs image or kernel (vmlinuz) from running server then server will run in
good condition till the reboot. Because the kernel or initrd image is present
on memory (RAM).
When we give reboot signal on server the kernel/initrd image
will get loaded back to HDD via RAM. And after reboot while the server coming
up, it (boot loader) will try to search kernel or iinitrd image to load on to
RAM from HDD but it will not get so the server will not come up.
The kernel (vmlinuz) or initrd
image is present under /boot directory or mountpoint.
[root@testmachine
boot]# ls -lrt |egrep -i "initrd|vmlinuz"
-rwxr-xr-x.
1 root root 4128944 Nov 11 2013 vmlinuz-2.6.32-431.el6.x86_64
-rwxr-xr-x 1 root root
4223504 Aug 10 2015
vmlinuz-2.6.32-573.3.1.el6.x86_64
-rw------- 1 root root
5965847 Aug 17 2015
initrd-2.6.32-431.el6.x86_64kdump.img
-rw------- 1 root root
5953546 Oct 8 2015
initrd-2.6.32-573.3.1.el6.x86_64kdump.img
In older version we were having
initrd (init ram disk) image and in newer version we have initramfs image. The
main purpose of this file is to mount / partition in read only mode.
*************************************************************
Query 2: How to view initramfs
image?
Ans: We can find the initramfs file
under /boot partition.
[root@testmachine
boot]# ls -lrt |grep -i initramfs
-rw-------.
1 root root 17551982 Jun 24 2015 initramfs-2.6.32-431.el6.x86_64.img
-rw------- 1 root root 28095966 Aug 17 2015 initramfs-2.6.32-573.3.1.el6.x86_64.img
In older version we were having
initrd (init ram disk) image and in newer version we have initramfs (init ram
filesystem) image. The main purpose of this file is to mount / partition in
read only mode. After mounting the / partition, it calls /sbin/init program
which is father of all processes in user space having PID=1 & start the
system initialization.
[root@testmachine
~]# pidof init
1
We can view content of initramfs
file by lsinitrd command.
[root@testmachine
~]# lsinitrd /boot/initramfs-2.6.32-573.3.1.el6.x86_64.img |more
Image:
/boot/initramfs-2.6.32-573.3.1.el6.x86_64.img: 27M
========================================================================
dracut-004-388.el6
========================================================================
drwxr-xr-x 26 root
root 0 Aug 17 2015 .
drwxr-xr-x 2 root
root 0 Aug 17 2015 bin
lrwxrwxrwx 1 root
root 4 Aug 17 2015 bin/awk -> gawk
-rwxr-xr-x 1 root
root 23720 Aug 17 2015 bin/basename
-rwxr-xr-x 1 root
root 906152 Aug 17 2015 bin/bash
-rwxr-xr-x 1 root
root 45224 Aug 17 2015 bin/cat
-rwxr-xr-x 1 root
root 116824 Aug 17 2015 bin/cp
-rwxr-xr-x 1 root
root 109672 Aug 17 2015 bin/dash
Thanks
& Regards,
Kirann Jadhav
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