Problems with crossbuilder

[nikalon]

I'm following this guide for compiling Ubuntu Touch packages. Setting up LXD with crossbuilder setup-lxd works well but when I execute the command crossbuilder in any project I get this error:

error: no devices/emulators found
Could not find a device, will not deploy
Building address-book-app for armhf.
Creating LXD container address-book-app-usdk-16-04-amd64-armhf-dev using ubports-sdk:ubuntu-sdk-16.04-amd64-armhf-dev.
Error: Remote ubports-sdk exists as <https://sdk-images.ubports.com>
Creating address-book-app-usdk-16-04-amd64-armhf-dev
Error: Failed container creation: LXD doesn't have a uid/gid allocation. In this mode, only privileged containers are supported.

I tried removing and reinstalling LXD, removing my previous containers, rebooting but nothing works. I'm using Pop!_OS based on Ubuntu 18.04.

[nikalon]

After a searching the internet I found out that I need to add the line root:100000:65536 into /etc/subuid and /etc/subgid.
I think that line is added automatically when installing LXD but for some reason it wasn't generated.

[nikalon]

And if someone wants to know why it's necessary it is well explained here and here.