[Nexus 6 Q&A, Help & Troubleshooting] extremx:
Hi,

I'll try and give as many details as possible. between me trying to get a root method to pass safteynet and updating to Nougat.

I manually updated to nougat as to not lose my data... ie: flashed radio, firmware, system, etc. First oddity was that twrp (twrp-3.0.2-0-shamu.img) would not stick unless i was rooted....weird. I also read I needed to rename recovery-from-boot.p to recovery-from-boot.bak and it would stick, though this made no difference, which i figured out why (coming up later). Ok, so i'm now rooted twrp and twrp is sticking. This is where i went to install the new pixel launcher as i was using nexus launcher before the update and was quite fond of it. I would flash the zip through twrp, but it would never show up as a system app. i tried and tried to get it there, to no avail. Ok, so i need to boot to recovery to access /system... sure, lets try that. I mount /system in twrp, flash the zip, use the file manager to check it out. It is showing in /system/priv-app. Cool. Boot phone, not there. :( Some weirdness is happening....

Twrp and /system are doing strange things...

While booted (truncated):

shamu:/ $ mount
/dev/block/dm-0 on /system type ext4 (ro,seclabel,relatime,data=ordered)

While in twrp:

~ # mount
/dev/block/mmcblk0p41 on /system type ext4 (rw,seclabel,relatime,data=ordered)

Why is one dm-0 and the other mmcblk0p41? Lets keep looking...

While booted:

shamu:/ $ ls /system/
app build.prop fake-libs framework lost+found priv-app usr xbin
bin etc fonts lib media recovery-from-boot.p vendor

While in twrp:

~ # ls /system/
app fonts priv-app
bin framework recovery-from-boot.bak
build.prop lib usr
etc lost+found vendor
fake-libs media xbin

Ah! i knew i changed the recovery-from-boot.p file! But.... why is it changed in the twrp /system and not the booted /system? That would explain why twrp kept getting overwritten. But whats going on here? Its like twrp is not mounting the right /system.... yet i can figure out how to mount the proper one.

While booted:

shamu:/data/data # mount -o rw,remount,rw /system
mount: '/dev/block/dm-0'->'/system': Device or resource busy

While in twrp:

~ # mount -o rw,remount,rw /system
mount: can't find /system in /proc/mounts
~ # mount /system
~ # mount
rootfs on / type rootfs (rw,seclabel)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=1506976k,nr_inodes=172637,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
tmpfs on /tmp type tmpfs (rw,seclabel,relatime,size=1506976k,nr_inodes=172637)
pstore on /sys/fs/pstore type pstore (rw,relatime)
adb on /dev/usb-ffs/adb type functionfs (rw,relatime)
/dev/block/mmcblk0p38 on /cache type ext4 (rw,seclabel,relatime,data=ordered)
/dev/block/dm-0 on /data type ext4 (rw,seclabel,relatime,data=ordered)
/dev/block/dm-0 on /sdcard type ext4 (rw,seclabel,relatime,data=ordered)
/dev/block/mmcblk0p41 on /system type ext4 (rw,seclabel,relatime,data=ordered)

I'm at a loss about what to do. I thought twrp was not decrypting properly, so i removed exchange and removed my pin code in case that was causing it. No change. Any help or advice would be appreciated. I really would like Pixel launcher and tethering :)

Specs:

Nexus 6 32gb

Android 7.0, Oct 5,2016

twrp-3.0.2-0-shamu.img

Phone is encrypted, no pin code to boot.

rooted with superuser-r266-hidesu, systemless with phh superuser gui