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Old 11-22-2012, 03:35 PM   #256
ixtab
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Posts: 2,903
Karma: 6677485
Join Date: Dec 2011
Device: K3, K4, K5, KPW, KPW2
Ahh... lots of questions

Quote:
Originally Posted by cryzed View Post
Okay, this sounds convincing. And I am sorry if I seem lazy or uneducated about this whole stuff but I couldn't actually find much information about the diags mode in the Wiki. What does this special system-partition(?) when booted into, allow me to do? With the rescue pack it basically provides me with a way to access my Kindle over SSH and possibly save it by replacing/deleting/modifying some files, given that I know what went wrong or even restore entire partitions. What does the diags partition do by default? nothing that could possibly unbrick the Kindle? I assume it's just a usually "useless" diagnostics partition which is used by the Amazon staff to check if the system is alright and you guys just modified that slightly with the rescue pack, as to allow full root access to the Kindle's file system over SSH additionally.
Umm... yes!
The kindle is actually a dual-boot system. Much like you can boot your PC into Windows or Linux, a Kindle can boot into diags and main (=normal mode). These two systems are "strictly" separated, so (most importantly), even if you completely destroy your main partition and/or kernel, diags still remains functional.*
Just actually boot into diags mode to see what its "normal" purpose is. It's really a "diagnostics" mode, where you can test all kinds of hardware and system functionality.

What "we" use it for is mostly as a "life insurance". If the diags partition can boot and enable SSH access, then we have full access to the device. And even if the main partition and/or kernel were completely FUBAR, we could still fix it. In the simplest case, that's just overwriting the main kernel and partition with working ones, but you can also just mount the main partition and selectively edit a file to fix a mistake, etc. You have all the power of a full Linux (well ok, busybox) system at hands.

(*) The restriction on the Paperwhite is that there is currently no known way to directly boot into diags, without requiring a functional main partition ("rescue pack" way) or at least u-boot ("serial connection" way).


Quote:
Originally Posted by cryzed View Post
From what I gather installing the regular USBNet is not important anymore after installing the rescue partition because I already have another way to enable SSH (by booting into diags mode) and creating back-ups of all system partitions would be a great idea too, so that, if I actually fuck something up, I can overwrite the partitions which I had previously backed up? Are the images provided by you, ixtab, here then just a way for people who did not back up their own partitions to save their Kindle by overwriting their partitions with your back-ups of them basically?
I think that there's a fundamental misunderstanding here, because you seem to imply that USB network access / SSH is only useful for backup purposes. You're probably right that this is indeed one of the major uses for the "average kindle user out there" who reads these mobileread threads, but that's only scratching the surface, and it's only because most people turn here when their device is already broken, and want to "repair" it.

What SSH really does is give you access to the OS of the device. And specifically, on the Kindles, it gives you full administrative access to the device. If you have a root shell on a Kindle, you can do *anything*. You can monitor what the device does, you can start your own applications, you can join a botnet, you can even have it display Mickey Mouse's face every minute, if you so desire. You can do *anything*.

To get this a bit more down-to-earth: where do you think all the modifications for the K3/K4/KT come from? They're not just "invented" in thin air and then magically work. Everything - starting from the jailbreak itself, and through to - to stay with an example that you know - Collections Manager, has been executed hundreds of times, while being logged in via SSH and watching the system behavior, and monitoring various log files.

In other words: there is a reason why usbNetwork is listed as the most important, and as the very first modification, right after the jailbreak: because *it is* the most important, and the most potent. The entire point is about remotely (USB) telling the device what to do (root). From there on, everything is easy...


Quote:
Originally Posted by cryzed View Post
Is there any good reason why I should still install USBNet after having installed the rescue pack? And after having updated to version 5.3.0 is it possible to basically revert to 5.2.0 by restoring all partitions that I have backed up (during the 5.2.0 state), or will this create problems?
Yes, keep usbnet installed. If you don't actually use it, it won't harm you in any way. But it still provides a safety net that you can enable when you need it.

Concerning 5.2.0 or 5.3.0: yes, provided that you do have a working diags partition with SSH (and that your main partition, be it 5.3.0 or 5.2.0, will actually let you boot to that partition [cf "rescue pack"]), you can always freely switch between versions.
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