I've been pretty much following the steps within the scripts found in https://github.com/ubports/device-builds, and after some code adjustments have been able to build ubp-5.1-allthefixings on my ubuntu 18.04 box.

However, now that I have the device_hammerhead_devel.tar.xz file ready, I am not sure of the next steps... Unfortunately I do not have the ubuntu-device-flash as that package did not exist under 18.04.

Can anyone explain the next steps? Do I fastboot into recovery, copy the xz files and install (similar to lineageOS)? Do I need to use some other tool to flash my nexus5?

So a follow up to this, for others...

After completing all the steps in https://github.com/ubports/device-builds, I then did the steps in https://docs.ubports.com/en/latest/porting/ubp-5.1.html

That is, reboot into fastboot and

fastboot flash boot boot.img
fastboot flash recovery recovery.img

Reboot to validate new kernel

uname -a
lsb_release -a
cat /proc/version

Then fastboot again and do

./replace-android-system system.img

From https://github.com/janimo/phablet-porting-scripts/blob/68734ca07998b8e784397df77d9aca4b968b3815/build/replace-android-system

In my Nexus5, I had to modify the script since I fastboot'ed already...

read -t 10 -n 1 -p "Reboot to recovery (y/n)? " answer
[ -z "$answer" ] && answer="Yes"  # if 'yes' have to be default choice
case ${answer:0:1} in
    y|Y )
        adb reboot recovery;
        wait_for_device;
    ;;
    * )
        echo "Assuming device in recovery mode";
    ;;
esac

Once you reboot into UT, you can validate the updated build properties...

cat /android/system/build.prop

which should match what you built on your machine!

@AppLee said:

Before I could last at most 8h now it's up to 36 hours.
Recently I had some battery leak, but nothing a reboot wouldn't solve or simply waiting.

Wut?! What configuration options do you have? I've tweaked my governor to be conservative, but even then I last less than 10 hours. What apps are you using? As far as I can tell, dekko is my biggest power consumer...