[Nexus 7 Q&A, Help & Troubleshooting] bftb0:
You have 83 posts - is there some reason you can not ask your question in the Toolkit thread? After all, it was the toolkit that got you here, right? Does the Toolkit dev offer customer support, or is it more a less "yer on your own" kinda deal?

At the moment it sounds like that partially-functioning recovery is the only hope that your tablet will be recovered, given the very odd behavior of being unable to get it to power up into fastboot mode. If you try to replace the recovery and that fails, there won't be anything left for you. That means that you should proceed very very carefully.

(I am also wondering why - if you can manually communicate with the tablet in recovery mode using adb - why exactly it is that the Toolkit can not do exactly the same thing.)

It is encouraging that your tablet is able to run shell commands via adb. That means you can do some things as root. So, I would start with an investigation that is completely non-destructive and changes nothing. So first:

What output do these command produce?

adb shell cat /proc/mounts
adb shell cat /proc/partitions

# carefully check to see if any read errors occur ANYWHERE from the eMMC flash memory device

adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/APP bs=1024 of=/dev/null
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/CAC bs=1024 of=/dev/null
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/LNX bs=1024 of=/dev/null
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/MDA bs=1024 of=/dev/null
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/MSC bs=1024 of=/dev/null
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/PER bs=1024 of=/dev/null
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/SOS bs=1024 of=/dev/null
# note if N7 is a 32 GB device, reading all of UDA takes a while (> 14 minutes) be patient
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/UDA bs=1024 of=/dev/null
adb shell dd if=/dev/block/platform/sdhci-tegra.3/by-name/USP bs=1024 of=/dev/null
adb shell dd if=/dev/block/mmcblk0boot0 bs=1024 of=/dev/null
adb shell dd if=/dev/block/mmcblk0boot1 bs=1024 of=/dev/null

The first command will just tell me whether TWRP sucessfully mounted /data or not. The second command will give me confidence there is nothing seriously wrong with the partitioning of your eMMC flash chip.

The rest of the commands (above) will attempt to read the entire device, partition by partition to see if you get read errors. (Note this is also non-destructive)

These next commands check to see if the "system" ext4 filesystems is corrupted or not. With the "-f -n" option, these are "check only" commands, no attempt will be made to fix or write changes.

adb shell e2fsck -f -n /dev/block/platform/sdhci-tegra.3/by-name/APP

If it is clean you will see output from the above like this:

e2fsck 1.41.12 (17-May-2010)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
APP: 4273/41664 files (0.2% non-contiguous), 94112/166400 blocks

If it has problems, you will see an incredible amount of output complaining about this and that.

OK, next, userdata partition (/data or UDA).

If it was mounted (see /proc/partitions output above) you will see two lines like this:

/dev/block/mmcblk0p9 /data ext4 rw,relatime,user_xattr,acl,barrier=1,data=ordered 0 0
/dev/block/mmcblk0p9 /sdcard ext4 rw,relatime,user_xattr,acl,barrier=1,data=ordered 0 0

If you don't see the above lines, then that means that the initial mount of /data that TWRP attempted failed, and you can run this check:

adb shell e2fsck -f -n /dev/block/platform/sdhci-tegra.3/by-name/UDA

to verify if the userdata (UDA) partition has a clean ext4 filesystem. As before, you will see a ton of messages if there is filesystem corruption.

OK, so far so good. Now some homework (above) for you. Cut-n-Paste your output into a reply. (Note: if the "e2fsck" program starts spewing tons and tons of error messages, I don't need to see that in a cut-n-paste.)

The above instructions fix nothing - but they will tell us if your tablet has further problems that need to be addressed before you start flashing things. I wouldn't be attempting any flashing until you are at least confident in the state of various partitions.

good luck - I have a feeling it is going to be needed

.