Boot loop after updating to official Android 6.0 Marshmallow on my Nexus 5 Last day I got the notification to download and install official Android 6.0 Marshmallow in my Nexus 5, which is not rooted, was running Android 5.1.1 and no custom ROM. As I downloaded and installed it, from that point its gone to boot loop state (the four dot animation is endlessly running).

I have already searched the web for solution like Boot loop after flashing Android 6.0 Marshmallow on my Nexus 5, Boot loop after flashing android 6.0 marshmallow on nexus 5 follow up and many more, but not tried. Because all those help seekers had tried to manually OS install or phone was rooted or already had custom ROM, but my Nexus 5 did not have any of those.

I had tried "wipe cache partition" and reboot, but it did not helped. As I don't had any data backup of my phone storage, the last thing I will be willing to do is "wipe data/factory reset". As my phone's usb debugging was enabled and I had adb in my desktop, so I have also tried to copy data from my phone using the "adb pull" command in boot looped mood. But also did not got any luck, may be "adp pull" command don't work in booting mood or I am doing something wrong with the command.

Any help to backup/recover the data or solution of the boot loop problem without "wipe data/factory reset" is appreciated. Thanks in advance.....
If your device is in a boot-loop you will not be able to pull anything. 
You might want to try and booting the phone into bootloader IF possible by pressing volume down and power to power on the device.
I would recommend downloading the factory image from Google, extracting it and trying:

fastboot flash bootloader bootloader-hammerhead-hhz12k.img


To flash the bootloader image in in the zip via the command line, as well as boot and radio just to be safe. DO NOT FLASH userdata.img or cache.img, or run any flash all batch or script as this WILL erase everything that is currently on your device.

OR:

You can try to follow the same instructions to boot to bootloader and:

fastboot flash recovery twrp-2.8.7.1-hammerhead.img


To install TeamWin Recovery, which you can download here.
This will give you a custom recovery you can then boot to and possibly be able to adb pull from there.

Hope this helps!!