Linux boot loading process

linux boot loading process

This procedure has room for improvements and optimizations, for example there’s too much memory copying here and there, where mostly everything can be executed in place. As usual, this is possible mainly due to the fact that all the tools are free and open source. It is anyway a nice exercise and a good starting point that reveals interesting details about the boot process in embedded systems.

With these modifications it works for me. I discovered this address my doing “md 0 64” and inspecting the data that looked like an address. You are right: I just tried and the ramdisk is placed at 0xd00000 instead. Then I misinterpreted the initrd parameter, it should be something like “initrd=0xd00000,2M“, where the value after the comma is the size of the ramdisk (I rounded by eccess).

With all 512 diodes in place, the memory contained all “one” bits; the card was programmed by cutting off each diode whose bit was to be “zero”. It consisted of a printed circuit card, the M792, that plugged into the Unibus and held a 32 by 16 array of semiconductor diodes. DEC also sold versions of the card, the BM792-Yx series, pre-programmed for many standard input devices by simply omitting the unneeded diodes. DEC later added an optional diode matrix read-only memory for the PDP-11 that stored a bootstrap program of up to 32 words (64 bytes).

Growth in the capacity of ROM has allowed ever more elaborate start up procedures to be implemented. The invention of read-only memory (ROM) of various types solved this paradox by allowing computers to be shipped with a start up program that could not be erased. [3][citation needed ]The usage calls attention to the requirement that, if most software is loaded onto a computer by other software already running on the computer, some mechanism must exist to load the initial software onto the computer. [4] Early computers used a variety of ad-hoc methods to get a small program into memory to solve this problem. Boot is short for bootstrap[1][2] or bootstrap load and derives from the phrase to pull oneself up by one’s bootstraps.

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The zeros were just a typo. Bin file as the rootfs. The patching was the issue. H i added
#define CONFIG_BOOTARGS “root=/dev/ram mem=128M rdinit=/sbin/init”
#define CONFIG_INITRD_TAG 1
didn’t add the bootm command as i had to create a larger flash. Hello , thanks for the reply. C file and added : || defined (CONFIG_VERSATILE)
and in the versatile. Nevertheless , it works fine. Instead this is what i did :
After looking through the patch file i modified the image. Uimg was over 3 MB , and so had different memory values.

In, Linux most of the drivers are pre-built as modules, these would be initial ram drive (initrd. Img) where it can keep all the information of additional modules. So, when the kernel boots, it creates ramdrive, loads the initrd. Img and its depended modules.

Feel free to configure unused run levels (commonly run level 4) as you see fit. This allows them to quickly move in and out of their custom configuration without disturbing the normal set of features at the standard run levels. Many users configure those run levels in a way that makes the most sense for them while leaving the standard run levels as they are by default.

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Setenv bootargs ‘console=ttyAMA0,115200n8 root=/dev/ram rw’
I have created uImage loaded at addr1 and created ramdisk of mkimage compatible loaded at
addr2 (addr1 > addr2). I missed to give you the details about boot args. I did below command
$ bootm $addr1 $addr2.

Thus setting the switches to 7004000400 and pressing the appropriate button would read the first card in the card reader into memory (op code 70), starting at address 400 and then jump to 400 to begin executing the program on that card. Another example was the IBM 650 (1953), a decimal machine, which had a group of ten 10-position switches on its operator panel which were addressable as a memory word (address 8000) and could be executed as an instruction.

For example, on a PC with Windows XP installed on the hard drive, the user could set the boot order to the one given above, and then insert a Linux Live CD in order to try out Linux without having to install an operating system onto the hard drive. In this example of dual booting, the user chooses by inserting or removing the CD from the computer, but it is more common to choose which operating system to boot by selecting from a BIOS or UEFI boot menu, by using the computer keyboard; the boot menu is typically entered by pressing Delete or F11 keys during the POST. This is an example of dual booting, in which the user chooses which operating system to start after the computer has performed its Power-on self-test (POST).

When you freshly set up a Linux distribution by hand, you get a lot of verbose output when booting into your system, but also install’n’go distributions like Ubuntu.

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