[LG G Watch R] lion567:
[MENTION=398245]LeeDroid[/MENTION], I'm sure you already know this :D , but it worth to mention that Urbane OTA ZIP (7252d535d6a18047daaf3bfd4745f1c86ef7e7f1.signed-bass-ota-2576000.zip) posted by [MENTION=1378823]AndiTails[/MENTION] contains complete Urbane 6.0.1 ROM (except recovery) - all bootloader staff, boot.img and complete system.img in so called Lollipop/Marshmallow DAT files sparse format (system.new.dat, system.transfer.list). BTW - system.patch.dat (updates file) is empty (zero length) that confirms completeness of ROM. You can convert system.new.dat to raw system.img file via sdat2img tool from [MENTION=5132229]xpirt[/MENTION] using blocks map file system.transfer.list.

sdat2img.py system.transfer.list system.new.dat system.img

Resulted system.img file can be flashed via fastboot, mounted (-o loop), if you have squashfs kernel module with lz4 support, or unpacked it with unsquashfs, so you can start rock and roll :D

One problem, I've just steped in, it seems that in 6.0.1 LG switched from ext4 filesystem to SquashFS compressed read-only file system for system partition, that resultes in raw system.img file is not ext4, but squashfs image :(

file system.img
system.img: Squashfs filesystem, little endian, version 4.0, 224820863 bytes, 1132 inodes, blocksize: 131072 bytes, created: Tue Feb 2 02:25:00 2016

and openSuSE 13.1 squashfs kernel module (squashfs: version 4.0 (2009/01/31) Phillip Lougher) don't recognise filesystem compression type :(

SQUASHFS error: Filesystem uses "unknown" compression.

Hope somebody can find solution, possibly via squashfs-tools or may be other Linux derivates has newer squashfs kernel module, so rock and roll can be started. ;)

PS. It seems that full dump wouldn't help in this case, because it'll contain the same squashfs filesystem image.

Update: Finally I've managed to build squashfs-tools v.4.3 with LZ4 support and successfully finished unpacking system.new.dat from OTA update 6.0.1

It contains SquashFS filesystem with LZ4 compression.

~/squashfs-tools/unsquashfs -v
unsquashfs version 4.3 (2014/05/12)
copyright (C) 2014 Phillip Lougher <phillip@squashfs.org.uk>

~/squashfs-tools/unsquashfs -s system.img
Found a valid SQUASHFS 4:0 superblock on system.img.
Creation or last append time Tue Feb 2 02:25:00 2016
Filesystem size 219551.62 Kbytes (214.41 Mbytes)
Compression lz4
Block size 131072
Filesystem is not exportable via NFS
Inodes are compressed
Data is compressed
Fragments are compressed
Always-use-fragments option is not specified
Xattrs are compressed
Duplicates are removed
Number of fragments 178
Number of inodes 1132
Number of ids 3

~/squashfs-tools/unsquashfs -d ./system -user-xattrs system.img
Parallel unsquashfs: Using 3 processors
1034 inodes (3093 blocks) to write

[==============================================================================================================================================================|] 3093/3093 100%

created 883 files
created 98 directories
created 151 symlinks
created 0 devices
created 0 fifos

grep fingerprint ./system/build.prop
# Do not try to parse description, fingerprint, or thumbprint
ro.build.fingerprint=lge/bass/bass:6.0.1/MEC23G/2576000:user/release-keys