Slimkat, suddenly won't boot - Galaxy S II Q&A, Help & Troubleshooting

Hi, my i9100 is on Slimkat (Slim-i9100-4.4.2.build.4-OFFICIAL-3666) -- and has been for a while, slightly over two months I believe.
Yesterday, after rebooting the phone it refused to boot -- it's stuck on the first boot screen, the one that says "Samsung Galaxy SII GT-I9100" and has the yellow triangle on it. It does react to power button, I can still turn off the phone this way. I did not do anything unusual lately, haven't tried installing anything.
I cannot access recovery:
Home+VolDown+Power -- brings up a Warning screen ("A custom OS can cause critical")
Home+VolUp+Power -- does nothing, the boot screen appears for 2 seconds, the phone reboots/ turns off
Any idea how:
diagnose the issue
retrieve data on internal SD
bring the phone back to usable state
Thanks!

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No recovery = your only option is back to stock via Odin/download mode. You shouldn't lose any data doing this, but it may not fix the problem on its own, you still may need to do a factory reset after doing this.
Only way to find out is to try it & see what happens. And no, you don't have any other options.

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Thanks a god, Download mode is working.
As say above flash stock ROM via Odin. Download: sammobile.com

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Can someone guide me to a suitable recovery? I've tried flashing "CWM-KitKatCompatible-i9100.tar" (which seemed like a good idea since the phone was already on KitKat) via Odin 3.09 however this did not quite work:
Code:
<ID:0/007> Added!!
<ID:0/007> Odin v.3 engine (ID:7)..
<ID:0/007> File analysis..
<ID:0/007> SetupConnection..
<ID:0/007> Initialzation..
<ID:0/007> Get PIT for mapping..
<ID:0/007> Firmware update start..
<ID:0/007> SingleDownload.
<ID:0/007> zImage
<ID:0/007> NAND Write Start!!
<ID:0/007> Complete(Write) operation failed.
<OSM> All threads completed. (succeed 0 / failed 1)
Can still enter download mode. Now I need a working recovery. Slimkat was on TWRP I believe however I can't seem to find a standalone version (flashable via Odin)

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No, that was not a good idea at all. Because you won't fix it that way.
You won't fix it by flashing recovery. You need to go back to stock, get it fixed, then you can re-root the phone & either restore a nandroid or reinstall a custom rom/kernel.
Also, if you flash a recovery independently of the kernel, it won't stick anyway & will disappear when you reboot.
So...You can either take the advice you've been given & fix your phone fairly quickly, or you can muck around for however long & live with a busted phone.
Problems with Odin flash = same as everyone else; find Hopper8's 'Odin troubleshooting' thread stickied in General & go through the troubleshooting steps in a methodical way as many times as you need to in order to get a successful flash.

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MistahBungle said:
No, that was not a good idea at all. Because you won't fix it that way.
You won't fix it by flashing recovery. You need to go back to stock, get it fixed, then you can re-root the phone & either restore a nandroid or reinstall a custom rom/kernel.
Also, if you flash a recovery independently of the kernel, it won't stick anyway & will disappear when you reboot.
Click to expand...
Click to collapse
I was hoping I can flash recovery and then immediately reflash Slimkat from it (which includes TWRP, kernel & ROM).
OK, I'll give stock a go first. But only after I sort out Odin.

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You're having that problem because recovery is busted. Flashing another custom recovery won't fix that. Only going back to stock which will give you a fresh stock recovery will fix the problem (and as I said in my PP, you might need to do a reset after).
I've given you the tools (Hopper's thread) to enable you to 'sort out Odin'. You need to pay more attention to what people have posted after you've asked for help.

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Update: I am unable to get Odin to flash the phone with latest stock. I've been through Odin problems in the past, with 3 different Samsung models and was able to resolve them. Not this time it seems, it's stuck on starting flashing boot.img however I try. Looking at forum responses this often requires a hardware replacement (mobo/ flash chip).
However: I've noticed I can (kind of) enter recovery. If I keep the VolUp+Home pressed long enough, it will ultimately get me to the following screen:
{
"lightbox_close": "Close",
"lightbox_next": "Next",
"lightbox_previous": "Previous",
"lightbox_error": "The requested content cannot be loaded. Please try again later.",
"lightbox_start_slideshow": "Start slideshow",
"lightbox_stop_slideshow": "Stop slideshow",
"lightbox_full_screen": "Full screen",
"lightbox_thumbnails": "Thumbnails",
"lightbox_download": "Download",
"lightbox_share": "Share",
"lightbox_zoom": "Zoom",
"lightbox_new_window": "New window",
"lightbox_toggle_sidebar": "Toggle sidebar"
}
-- but it doesn't go any further, it just stays there. What's more it reboots within 5-10 minutes.
BUT!
When I connect the phone to PC, my Win7 says it installed 2x
Code:
"Linux File-CD Gadget USB Device"
It doesn't show up as a drive unfortunately.
If I do
Code:
adb devices
on my PC, it does detect it:
Code:
* daemon not running. starting it now on port 5037 *
* daemon started successfully *
List of devices attached
0123456789ABCDEF recovery
I can't connect or do
Code:
adb shell
because I get:
Code:
- exec '/system/bin/sh' failed: No such file or directory (2) -
But I am able to do
Code:
adb pull /proc/cpuinfo
Not sure if partitions got mounted properly, especially the emmc sdcard but -- what's the easiest way to browse the filesystem via adb now and hopefully retrieve some data from the phone?