how to track the step of linux Startup

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http://stackoverflow.com – i wanna totally understand the linux startup step by step, which means i wanna stop the system when i want and resume it after that. just like gdb stuff so that i am able to see the registers or internal things of that. i am using Ubuntu distribution and i'm a newbee. while i have read the books like Understanding the linux kernel and the source code of linux. I just wanna touch it by my eyes to understand what's going on there. Any help would be very appreciated. Just like what i need to install or what i need to read or what i need to do or anything else. Thanks in advance! (HowTos)