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Old 07-08-2012, 04:20 AM   #1
manoj7410
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Question Study about Kernel bootup..


hi..
I want to know the complete boot process of linux kernel after the step of bringing the kernel image into the RAM.
.
.
I mean, I have studied about first stage/middilestage and second stage boot loaders... but what happens inside the RAM with kernel image.. who starts the kernel??
I came to know that init/main.c is the source for it..
.
.
Can I get some links to study about it... ??

Thanks

Maddy
 
Old 07-08-2012, 05:45 AM   #2
pixellany
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Google is your friend:
http://www.google.com/search?q=linux...ient=firefox-a

short answer: kernel is loaded into RAM and de-compressed, then the boot loader transfers control to the kernel. The kernel then calls "init"
 
Old 07-08-2012, 06:43 AM   #3
manoj7410
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Quote:
Originally Posted by pixellany View Post
Google is your friend:
http://www.google.com/search?q=linux...ient=firefox-a

short answer: kernel is loaded into RAM and de-compressed, then the boot loader transfers control to the kernel. The kernel then calls "init"
Thanks but I already know that... I want to know how exactly init started..??
 
Old 07-08-2012, 06:46 AM   #4
pixellany
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???
the kernel issues the "init" command, and the init program starts running. It uses /etc/inittab to set specific configurations.

Or maybe I don't understand your question.......
 
Old 07-08-2012, 06:53 AM   #5
manoj7410
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Quote:
Originally Posted by pixellany View Post
???
the kernel issues the "init" command, and the init program starts running. It uses /etc/inittab to set specific configurations.

Or maybe I don't understand your question.......
My question is:
my second stage boot loadar fetches the kernel and put it into RAM, Now very first task that happens is start_kernel(). That is available in kernel/init/main.c .... I want to understand the working of the start_kernel()... I think it will be clear to you now..
.
 
Old 07-08-2012, 07:02 AM   #6
pixellany
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OK---it seems that you are reading the source code. (You have more patience than I do....)

I will GUESS that the function "start_kernel()" will either call "init"--or it will call some other function which in turn calls init.

Have you read any of the links that Google found? If the answer is not there, then your options include:
---read the source code
---buy a book on the kernel---eg this one: http://www.google.com/url?sa=t&rct=j...PTDaEA&cad=rja
 
Old 07-08-2012, 07:12 AM   #7
manoj7410
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Quote:
Originally Posted by pixellany View Post
OK---it seems that you are reading the source code. (You have more patience than I do....)

I will GUESS that the function "start_kernel()" will either call "init"--or it will call some other function which in turn calls init.

Have you read any of the links that Google found? If the answer is not there, then your options include:
---read the source code
---buy a book on the kernel---eg this one: http://www.google.com/url?sa=t&rct=j...PTDaEA&cad=rja
thanks..
you are right about involking init through start_kernel().. but starting init is the last step of start_kernel().. What happens before that..??
No one is helping me...
.
.
Even books are not defining it. every place is providing the code of internal functions but not the theortical functionality of those functions. well,
thanks again.
 
Old 07-08-2012, 10:44 AM   #8
pixellany
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If it's not in the books, then you may just have to hunker down and read the code. Without really knowing anything about the kernel, I'll guess that the early stages are all about detecting hardware, setting up drivers, and initializing data structures in RAM. I would be surprised if a good book on the kernel did not give some flow charts to show what is happening.
 
  


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