Quote:
Originally Posted by rynax
Other than the diags partition,
do you need a main kernel in "kernel" or a diags kernel in "diags_kernel" or both to be able to go into diags mode?
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The K4 & K5 implement an embedded Linux version of a "Dual Boot" computer. U-boot (the bootloader) is a "multiboot", bootloader.
Same principle as setting up your PC as "dual boot", to boot either Linux or Windows.
You can boot Linux and use it to fix Windows;
You can boot Windows and use it to break Linux.
Earlier Kindles also are setup as a "Dual Boot" computer. It those they boot either the regular system or a memory resident system.
An embedded Linux version of being able to boot your "rescue" system from your LiveCD.
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*nix nit:
The inode file systems used by *nix systems have a very strong separation between the file system naming (directory) system and the file system data storage system.
This allows a file that is open and in use to be deleted and replaced without disturbing the programs that have it (the old one) open and in use.
The "delete and replace"
name in the directory is separate from the "delete and replace" of the
data.
On a system without constrained media storage size, not a problem to have two copies (old and new) of a file present at the same time.
On a system with highly constrained storage size (a small, fixed size, flash memory) this behavior when updating will cause you to run out of room in a hurry.
So the practice in the embedded Linux world is to have two bootable systems, where the one running is used to update the one that is not running. I.E: None of the files being replaced or changed are open and running.
That lets both the name and the data storage of a file to be deleted and replaced without using double of the storage area.
Windows does not work like that. They do things their way.
In Windows, you'll eventually get a "system restart required" message.
If you watch the progress message while your *nix package manager does a system update, you will see (if required) a four step sequence:
- installing new xyz
- ldconfig updated
- xyz stopped
- xyz started
Rather than a "you must now reboot" message.