opkg update && opkg install ca-certificates zsh curl git-http
sh -c "$(curl -fsSL https://raw.githubusercontent.com/robbyrussell/oh-my-zsh/master/tools/install.sh)"
Edit /etc/passwd and change root:x:0:0:root:/root:/bin/ash
to root\\:x:0:0:root:/root:/bin/zsh
Reboot, all done.