How to set 1024x600 HDMI resolution

Hello, dear BPI team! Help please, how to setup HDMI resolution to 1024x600 in Ubuntu image? Where are stored current uEnv & dts files?

Thanks!

UPD. I mean, how to cretate own (customized) file for bpi-bootsel. For example: /usr/lib/u-boot/bananapi/bpi-m64/u-boot-with-dtb-bpi-m64-lcd7-8k.img.gz