[G3 Q&A, Help & Troubleshooting] jbaldwin9182:
Friend got a g3 (d852 Canadian version, came with Lollipop), offered to help him install a debloated ROM on it because it came with McAfee and he didn't want it. Gave him instructions over skype, wound up with a brick instead after installing TWRP via AutoRec and rebooting.

Came over to his house to check it out and:

* It won't boot normally

* TWRP boots but will not mount (claims all partitions are 0MB), wipe, install ROMs, or update itself

* Can be put into download mode, tried flashing stock via both TOT and KDZ method, LG's tools complain about GPT and partition table problems in Engrish and fail.

Decided to delve into the shell and now I'm surprised it works at ALL. There's no block devices in /dev/block/*. I'd blame the kernel in TWRP (apparently some people have problems with encryption with old versions of TWRP though AFAIK this phone doesn't ship encrypted) but given download mode is having problems too I doubt that's the case. Starting to suspect a hardware problem, just triggered by the TWRP flash.

TWRP startup logs:

__bionic_open_tzdata: couldn't find any tzdata when looking for localtime!
__bionic_open_tzdata: couldn't find any tzdata when looking for GMT!
__bionic_open_tzdata: couldn't find any tzdata when looking for posixrules!
Starting TWRP 2.8.6.1 on Fri Jan 2 19:47:29 1970
(pid 185)
BOARD_HAS_NO_REAL_SDCARD := true
RECOVERY_SDCARD_ON_DATA := true
TW_NO_USB_STORAGE := true
TW_INCLUDE_CRYPTO := true
I:Found brightness file at '/sys/devices/f9967000.i2c/i2c-0/0-0036/backlight/lm3697/brightness'
I:TWFunc::Set_Brightness: Setting brightness control to 255
Starting the UI...Pixel format: 1440x2560 @ 32bpp
Pixel format: RGBX_8888
Not using qualcomm overlay, 'mdssfb_80000'
framebuffer: fd 4 (1440 x 2560)
I:Scaling the curtain width 1.333333x and height 1.333333x
=> Linking mtab
Moving /etc/twrp.fstab -> /etc/recovery.fstab
=> Processing recovery.fstab
I:Processing '/boot'
E:Unable to find partition size for '/boot'
I:Processing '/system'
I:Processing '/data'
I:Setting up '/data' as data/media emulated storage.
I:Created '/sdcard' folder.
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
E:Primary block device '/dev/block/platform/msm_sdcc.1/by-name/userdata' for mount point '/data' is not present!
E:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
E:Unable to recreate /data/media folder.
I:Processing '/cache'
I:Unable to mount '/cache'
I:Actual block device: '', current file system: 'ext4'
I:Processing '/recovery'
E:Unable to find partition size for '/recovery'
I:Processing '/efs1'
E:Unable to find partition size for '/efs1'
I:Processing '/efs2'
E:Unable to find partition size for '/efs2'
I:Processing '/radio'
E:Unable to find partition size for '/radio'
I:Processing '/rpm'
E:Unable to find partition size for '/rpm'
I:Processing '/tz'
E:Unable to find partition size for '/tz'
I:Processing '/external_sd'
I:Created '/external_sd' folder.
I:Processing '/usb-otg'
I:Created '/usb-otg' folder.
I:Backup folder set to '/data/media/TWRP/BACKUPS/LGD852d1e0ced5'
I:Settings storage is '/data/media'
Updating partition details...
E:Unable to mount '/system'
I:Actual block device: '', current file system: 'ext4'
E:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
E:Unable to mount '/cache'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/external_sd'
I:Actual block device: '', current file system: 'vfat'
I:Unable to mount '/usb-otg'
I:Actual block device: '', current file system: 'vfat'
...done
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
E:Unable to mount storage.
I:Unmounting main partitions...

Partition Logs:
/boot | | Size: 0MB
Flags: Can_Be_Backed_Up Can_Flash_Img
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/boot
Display_Name: Boot
Storage_Name: boot
Backup_Path: /boot
Backup_Name: boot
Backup_Display_Name: Boot
Storage_Path: /boot
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/system | | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB
Flags: Can_Be_Mounted Can_Be_Wiped Can_Be_Backed_Up Wipe_Available_in_GUI
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/system
Display_Name: System
Storage_Name: System
Backup_Path: /system
Backup_Name: system
Backup_Display_Name: System
Storage_Path: /system
Current_File_System: ext4
Fstab_File_System: ext4
Backup_Method: files

/data | | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB
Flags: Can_Be_Mounted Can_Be_Wiped Can_Be_Backed_Up Wipe_During_Factory_Reset Wipe_Available_in_GUI Can_Be_Encrypted Has_Data_Media Can_Encrypt_Backup Use_Userdata_Encryption Is_Storage
Symlink_Path: /data/media
Symlink_Mount_Point: /sdcard
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/userdata
Display_Name: Data
Storage_Name: Internal Storage
Backup_Path: /data
Backup_Name: data
Backup_Display_Name: Data
Storage_Path: /data/media
Current_File_System: ext4
Fstab_File_System: ext4
Backup_Method: files
MTP_Storage_ID: 65537

/cache | | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB
Flags: Can_Be_Mounted Can_Be_Wiped Can_Be_Backed_Up Wipe_During_Factory_Reset Wipe_Available_in_GUI
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/cache
Display_Name: Cache
Storage_Name: Cache
Backup_Path: /cache
Backup_Name: cache
Backup_Display_Name: Cache
Storage_Path: /cache
Current_File_System: ext4
Fstab_File_System: ext4
Backup_Method: files

/recovery | | Size: 0MB
Flags: Can_Flash_Img
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/recovery
Display_Name: Recovery
Storage_Name: recovery
Backup_Path: /recovery
Backup_Name: recovery
Backup_Display_Name: Recovery
Storage_Path: /recovery
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/efs1 | | Size: 0MB
Flags: Can_Be_Backed_Up Has_SubPartition
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/modemst1
Display_Name: EFS
Storage_Name: EFS
Backup_Path: /efs1
Backup_Name: efs1
Backup_Display_Name: EFS
Storage_Path: /efs1
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/efs2 | | Size: 0MB
Flags: Can_Be_Backed_Up Is_SubPartition
SubPartition_Of: /efs1
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/modemst2
Display_Name: efs2
Storage_Name: efs2
Backup_Path: /efs2
Backup_Name: efs2
Backup_Display_Name: efs2
Storage_Path: /efs2
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/radio | | Size: 0MB
Flags: Can_Be_Backed_Up Has_SubPartition
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/modem
Display_Name: Modem
Storage_Name: Modem
Backup_Path: /radio
Backup_Name: radio
Backup_Display_Name: Modem
Storage_Path: /radio
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/rpm | | Size: 0MB
Flags: Can_Be_Backed_Up Is_SubPartition
SubPartition_Of: /radio
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/rpm
Display_Name: rpm
Storage_Name: rpm
Backup_Path: /rpm
Backup_Name: rpm
Backup_Display_Name: rpm
Storage_Path: /rpm
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/tz | | Size: 0MB
Flags: Can_Be_Backed_Up Is_SubPartition
SubPartition_Of: /radio
Primary_Block_Device: /dev/block/platform/msm_sdcc.1/by-name/tz
Display_Name: tz
Storage_Name: tz
Backup_Path: /tz
Backup_Name: tz
Backup_Display_Name: tz
Storage_Path: /tz
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/external_sd | | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB
Flags: Can_Be_Mounted Can_Be_Wiped Wipe_Available_in_GUI Removable Is_Storage
Primary_Block_Device: /dev/block/mmcblk1p1
Alternate_Block_Device: /dev/block/mmcblk1
Display_Name: External SD
Storage_Name: External SD
Backup_Path: /external_sd
Backup_Name: external_sd
Backup_Display_Name: External SD
Storage_Path: /external_sd
Current_File_System: vfat
Fstab_File_System: vfat
Backup_Method: files
MTP_Storage_ID: 65538

/usb-otg | | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB
Flags: Can_Be_Mounted Can_Be_Wiped Wipe_Available_in_GUI Removable Is_Storage
Primary_Block_Device: /dev/block/sda1
Alternate_Block_Device: /dev/block/sda
Display_Name: USB-OTG
Storage_Name: USB-OTG
Backup_Path: /usb-otg
Backup_Name: usb-otg
Backup_Display_Name: USB-OTG
Storage_Path: /usb-otg
Current_File_System: vfat
Fstab_File_System: vfat
Backup_Method: files
MTP_Storage_ID: 65539

I:Loading package: TWRP (/script/ui.xml)
I:Load XML directly
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
E:Unable to mount /data/media during GUI startup.
I:Loading package: TWRP (/twres/ui.xml)
I:Load XML directly
I:Checking resolution...
I:Scaling theme width 1.333333x and height 1.333333x, offsets x: 0 y: 0
I:Loading resources...
open_png /twres/images/twrplogo.png
libpng warning: iCCP: Not recognizing known sRGB profile that has been edited
open_png /twres/images/menu-button.png
open_png /twres/images/file.png
open_png /twres/images/folder.png
open_png /twres/images/slideout.png
open_png /twres/images/indeterminate001.png
open_png /twres/images/indeterminate002.png
open_png /twres/images/indeterminate003.png
open_png /twres/images/indeterminate004.png
open_png /twres/images/indeterminate005.png
open_png /twres/images/indeterminate006.png
open_png /twres/images/indeterminate007.png
open_png /twres/images/progress_empty.png
open_png /twres/images/progress_fill.png
open_png /twres/images/checkbox_empty.png
open_png /twres/images/checkbox_checked.png
open_png /twres/images/radio_empty.png
open_png /twres/images/radio_selected.png
open_png /twres/images/medium-button.png
open_png /twres/images/sort-button.png
open_png /twres/images/minus-button.png
open_png /twres/images/plus-button.png
open_png /twres/images/home-icon.png
open_png /twres/images/back-icon.png
open_png /twres/images/slider.png
open_png /twres/images/slider-used.png
open_png /twres/images/slider-touch.png
open_png /twres/images/unlock.png
open_png /twres/images/keyboard1.png
open_png /twres/images/keyboard2.png
open_png /twres/images/keyboard3.png
open_png /twres/images/keyboard4.png
open_png /twres/images/cursor.png
I:Loading variables...
I:Loading mouse cursor...
I:Loading pages...
I:PageSet::CheckInclude loading filename: '/twres/portrait.xml'
I:Loading included resources...
I:Loading included variables...
I:Loading mouse cursor...
I:Loading included pages...
I:Loading page main
I:Loading page main2
I:Loading page install
I:Loading page flash_confirm
I:Loading page flash_zip
I:Loading page flash_done
I:Loading page install_image
I:Loading page flashimage_confirm
I:Loading page clear_vars
I:Loading page confirm_action
I:Loading page action_page
I:Loading page singleaction_page
I:Loading page action_complete
I:Loading page filecheck
I:Loading page rebootcheck
I:Loading page wipe
I:Loading page advancedwipe
I:Loading page formatdata
I:Loading page formatdata_confirm
I:Loading page checkpartitionlist
I:Loading page partitionoptions
I:Loading page refreshfilesystem
I:Loading page selectfilesystem
I:Loading page backup
I:Loading page backupname1
I:Loading page backupname2
I:Loading page backupencryption
I:Loading page backupencryption2
I:Loading page checkbackuppassword
I:Loading page backup_run
I:Loading page restore
I:Unable to open '/data/media/TWRP/BACKUPS/LGD852d1e0ced5'
I:Loading page restore_read
I:Loading page restore_decrypt
I:Loading page try_restore_decrypt
I:Loading page restore_select
I:Loading page renamebackup
I:Loading page restore_run
I:Loading page selectstorage
I:Loading page mount
I:Loading page usb_mount
I:Loading page usb_umount
I:Loading page reboot
I:Loading page settings
I:Loading page timezone
I:Loading page screen
I:Loading page Vibrate
I:Loading page advanced
I:Loading page partsdcard
I:Loading page htcdumlock
I:Loading page lock
I:Loading page filemanagerlist
I:Loading page filemanageroptions
I:Loading page choosedestinationfolder
I:Loading page filemanagerrenamefile
I:Loading page filemanagerrenamefolder
I:Loading page filemanagerchmod
I:Loading page filemanagerconfirm
I:Loading page filemanageracction
I:Loading page decrypt
I:Loading page decrypt_pattern
I:Loading page trydecrypt
I:Loading page terminalfolder
I:Loading page terminalcommand
I:Loading page sideload
I:Loading page fixperms
I:Loading page installsu
I:Set page: 'clear_vars'
I:Set page: 'main2'
I:Switching packages (TWRP)
SELinux contexts loaded from /file_contexts
E:Unable to mount '/cache'
I:Actual block device: '', current file system: 'ext4'
I:Could not check /cache/recovery SELinux contexts, using /sbin/teamwin instead which may be inaccurate.
Full SELinux support is present.
E:Unable to mount '/cache'
I:Actual block device: '', current file system: 'ext4'
E:Cannot load volume /misc!
E:Cannot load volume /misc!
Startup Commands:
ro.adb.secure=0
ro.com.google.clientidbase=android-google
ro.com.android.dateformat=MM-dd-yyyy
ro.com.android.dataroaming=true
ro.com.android.wifi-watchlist=GoogleGuest
ro.url.legal=<link removed because of XDA new user restrictions>
ro.boot.emmc=true
ro.boot.baseband=msm
ro.boot.hardware=g3
ro.boot.serialno=LGD852d1e0ced5
ro.boot.bootdevice=msm_sdcc.1
ro.boot.dlcomplete=0
ro.omni.device=d852
ro.omni.version=5.0.2-20150326-d852-HOMEMADE
ro.twrp.boot=1
ro.twrp.version=2.8.6.1
ro.wifi.channels=
ro.allow.mock.location=0
ro.board.platform=
ro.build.id=LRX22G
ro.build.date=Thu Mar 26 14:45:46 EDT 2015
ro.build.date.utc=0
ro.build.host=777jon
ro.build.tags=test-keys
ro.build.type=userdebug
ro.build.user=777jon
ro.build.display.id=omni_d852-userdebug 5.0.2 LRX22G eng.777jon.20150326.144459 test-keys
ro.build.product=d852
ro.build.version.sdk=21
ro.build.version.release=5.0.2
ro.build.version.codename=REL
ro.build.version.incremental=eng.777jon.20150326.144459
ro.build.version.all_codenames=REL
ro.build.description=omni_d852-userdebug 5.0.2 LRX22G eng.777jon.20150326.144459 test-keys
ro.build.fingerprint=LG/omni_d852/d852:5.0.2/LRX22G/777jon03261445:userdebug/test-keys
ro.build.characteristics=default
ro.config.ringtone=Orion.ogg
ro.config.alarm_alert=Argon.ogg
ro.config.notification_sound=pixiedust.ogg
ro.dalvik.vm.native.bridge=0
ro.secure=1
ro.zygote=zygote32
ro.carrier=unknown
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.cpu.abilist=armeabi-v7a,armeabi
ro.product.cpu.abilist32=armeabi-v7a,armeabi
ro.product.cpu.abilist64=
ro.product.name=omni_d852
ro.product.board=MSM8974
ro.product.brand=LG
ro.product.model=LG-D852
ro.product.device=d852
ro.product.locale.region=US
ro.product.locale.language=en
ro.product.manufacturer=LG
ro.baseband=msm
ro.bootmode=unknown
ro.hardware=g3
ro.revision=10
ro.serialno=LGD852d1e0ced5
ro.bootloader=unknown
ro.debuggable=1
ro.modversion=OmniROM-5.0.2-20150326-d852-HOMEMADE
ro.factorytest=0
ro.setupwizard.enterprise_mode=1
net.bt.name=Android
net.change=net.bt.name
init.svc.adbd=running
init.svc.healthd=running
init.svc.ueventd=running
init.svc.recovery=running
init.svc.set_permissive=stopped
twrp.crash_counter=0
dalvik.vm.isa.arm.features=div
dalvik.vm.lockprof.threshold=500
dalvik.vm.dex2oat-Xms=64m
dalvik.vm.dex2oat-Xmx=512m
dalvik.vm.stack-trace-file=/data/anr/traces.txt
dalvik.vm.image-dex2oat-Xms=64m
dalvik.vm.image-dex2oat-Xmx=64m
persist.sys.usb.config=adb
persist.sys.dalvik.vm.lib.2=libart.so
persist.sys.root_access=1
service.adb.root=1
keyguard.no_require_sim=true

I:Unable to mount '/cache'
I:Actual block device: '', current file system: 'ext4'
I:Failed to mount /cache for TWFunc::Update_Log_File
E:Unable to mount '/cache'
I:Actual block device: '', current file system: 'ext4'
tw_get_context failed to get selinux context
I:Failed to get default contexts and file mode for storage files.
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
E:Unable to mount /data/media/TWRP/.twrps when trying to read settings file.
I:Attempt to load settings from settings file...
I:Settings file '/data/media/TWRP/.twrps' not found.
I:Unable to mount '/cache'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '' to write version number.
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Unable to mount '/external_sd'
I:Actual block device: '', current file system: 'vfat'
I:Unable to mount '/usb-otg'
I:Actual block device: '', current file system: 'vfat'
__bionic_open_tzdata: couldn't find any tzdata when looking for CST6CDT!
__bionic_open_tzdata: couldn't find any tzdata when looking for posixrules!
I:TWFunc::Set_Brightness: Setting brightness control to 255
I:TWFunc::Fixup_Time: Pre-fix date and time: 1970-01-02--14-47-33
I:TWFunc::Fixup_Time: Setting time offset from file /sys/class/rtc/rtc0/since_epoch
I:TWFunc::Fixup_Time: will attempt to use the ats files now.
I:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
I:Enabling MTP during startup
I:Starting MTP
Starting MTP
E:Unable to mount '/data'
I:Actual block device: '', current file system: 'ext4'
MTP Enabled
I:Switching packages (TWRP)
created new mtpserver object
MtpServer::run fd: 14

Poking around via adb

adb shell
~ # twrp
TWRP openrecoveryscript command line tool, TWRP version 2.8.6.1

Allows command line usage of TWRP via openrecoveryscript commands.
Some common commands include:
install /path/to/update.zip
backup BSDC backupname
restore backupname BSDC
factoryreset
wipe cache
sideload
set variable value
get variable
decrypt password

See more documentation at <link removed because of XDA new user restrictions>
~ # uname -a
Linux localhost 3.4.0-CM-gab802aa #1 SMP PREEMPT Sun Mar 1 12:16:41 EST 2015 armv7l GNU/Linux
~ # df
Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 1447288 16 1447272 0% /dev
tmpfs 1447288 32 1447256 0% /tmp
~ # ls /dev/block/
loop0
loop1
loop2
loop3
loop4
loop5
loop6
loop7
ram0
ram1
ram10
ram11
ram12
ram13
ram14
ram15
ram2
ram3
ram4
ram5
ram6
ram7
ram8
ram9
zram0
~ # ls /proc
1
100
101
102
103
104
105
106
107
108
109
11
110
114
115
116
117
118
119
12
120
121
122
123
124
127
128
129
13
130
131
132
133
134
135
136
14
15
157
158
159
16
160
161
162
167
168
169
17
170
172
173
174
175
178
18
180
181
182
183
185
186
19
190
191
196
2
20
205
208
21
22
23
240
241
247
25
26
27
28
29
3
30
31
32
33
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
5
50
51
52
53
54
55
56
57
58
59
6
60
61
62
63
64
65
66
67
68
69
7
70
71
72
73
74
75
76
8
9
95
96
97
98
99
asound
buddyinfo
bus
cgroups
cmdline
consoles
cpu
cpuinfo
crypto
devices
diskstats
driver
execdomains
fb
filesystems
fs
interrupts
iomem
ioports
irq
kallsyms
key-users
kmsg
kpagecount
kpageflags
loadavg
locks
meminfo
misc
mounts
msm_pm_stats
net
pagetypeinfo
partitions
sched_debug
scsi
self
slabinfo
softirqs
spd
stat
swaps
sys
sysrq-trigger
sysvipc
timer_list
timer_stats
tty
uid_stat
uptime
version
vmallocinfo
vmstat
zoneinfo
~ # cat /proc/mounts
rootfs / rootfs rw 0 0
tmpfs /dev tmpfs rw,seclabel,nosuid,relatime,size=1447288k,nr_inodes=84924,mode=755 0 0
devpts /dev/pts devpts rw,seclabel,relatime,mode=600 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,seclabel,relatime 0 0
selinuxfs /sys/fs/selinux selinuxfs rw,relatime 0 0
tmpfs /tmp tmpfs rw,seclabel,relatime,size=1447288k,nr_inodes=84924 0 0
~ # cat /proc/partitions
major minor #blocks name

Current plan is to have him take it back to PC Mobile (Telus reseller) and play dumb if we can't figure out a fix.