To update boot codes.

The file to edit resides on the boot partition. Typically this is the sdcard mmcblk0p1
$ sudo -s
# mount /mnt/mmcblk0p1
# cd /mnt/mmcblk0p1
# vi bootcmd.src

Look for the line with nozswap and then continue the line with desired boot codes, e.g.,

waitusb=5:LABEL=mypen tce=LABEL=mypen tz=PST+8PDT,M3.2.0/2,M11.1.0/2 desktop=flwm_topside

# update_ubootcmd.sh

When successfully completed, reboot to effect.
# reboot