I just got my Dragonboard 820c and it boots fine with its initial boot, but it’s on an older kernel than I would like. So I follow this tutorial and created a boot.img with kernel 5.4, but now I am on the regular fastboot instructions and I am stuck. My board won’t go into fastboot mode, when I hold (-) and start up my board it will just restart and never do as its supposed to.
I then go into terminal and type
cat /dev/zero > /dev/disk/by-partlabel/boot but I get “Permissions Denied”, I tried to sudo it but get the same result. I tried to chmod /dev but the same result. I tried to superuser but I do not know the password and it is not
Once I get passed this step, I am also unsure what to do with my boot.img
Any advice would be helpful.