Busybox Init

[Rajeev Bansal]

Hello Walter,

Please see below mentioned text which I extracted from 
"ramfs-rootfs-initramfs.txt"

What is initramfs?
83 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#83>	------------------
84 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#84>	
85 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#85>	All 2.6 Linux kernels contain a gzipped "cpio" format archive, which is
86 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#86>	extracted into rootfs when the kernel boots up.  After extracting, the kernel
87 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#87>	checks to see if rootfs contains a file "init", and if so it executes it as PID
88 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#88>	1.  _*If found, this init process is responsible for bringing the system the
89 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#89>	rest of the way up, including locating and mounting the real root device (if
90 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#90>	any).*_  If rootfs does not contain an init program after the embedded cpio
91 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#91>	archive is extracted into it, the kernel will fall through to the older code
92 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#92>	to locate and mount a root partition, then exec some variant of /sbin/init
93 <http://www.mjmwired.net/kernel/Documentation/filesystems/ramfs-rootfs-initramfs.txt#93>	out of that.


So according to them , its init responsibility to mount the real root 
device, I think VI init works in that way, but not sure about the 
busybox Init. Can anyone clarify me that?

I have post my question to LFS also.

Thanks
Rajeev Bansal.

walter harms wrote:
> Rajeev Bansal wrote:
>   
>> Hi Mike,
>>
>> Thanks for replying the query.
>>
>> I am not sure about this but don't you think when you run the command 
>> switchroot in init script, then its Init's job to remount the previous 
>> mounted root with read-write options.
>>
>> Thanks
>> -Rajeev
>>
>>     
>
>
> hi Rajeev,
> from 'man init'
>        Init  is  the  parent  of all processes.  Its primary role is to create
>        processes from a script stored in  the  file  /etc/inittab  (see  init-
>        tab(5)).   This file usually has entries which cause init to spawn get-
>        tys on each line that users can log in.  It  also  controls  autonomous
>        processes required by any particular system.
>
> obviously it is NOT the job of init to mount anything or even to know about mounting.
> he is starting and supervising processes nothing more. doing a UNIX from scratch is
> a huge undertaking. People from "linux from scratch" are much more prepared (and
> capable) than the busybox ml to explain details of a system start-up.
> see: http://www.linuxfromscratch.org/
>
> re,
>  wh
>
>
>   



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