Editing the kernel command line parameters

To edit the kernel command-line, you need to edit /boot/boot.txt. You'll need to be root to do this.

[alarm@pinephone ~]$ cd /boot
[alarm@pinephone ~]$ sudo su
[sudo] password for alarm: 
[root@pinephone boot]# vi boot.txt

Look for the line setenv bootargs...

...
    setenv bootdir "/boot"
fi

setenv bootargs loglevel=3 console=${console} console=tty0 root=/dev/mmcblk${linux_mmcdev}p${rootpart} rw rootwait bootsplash.bootfile=bootsplash-themes/danctnix/bootsplash

echo "Loading kernel..."
...

Change it to whatever you need, save your changes, and exit.
Finally, run ./mkscr from within /boot.

[root@pinephone boot]# ./mkscr