Android

CID

CID would appear to stand for 'Country ID' - but LTE users have found flashing a different number CID firmware (than their original) broke network support. More here.
CID6 = XT1031 - CDMA (Republic Wireless US)
CID7 = XT1032 - European Global GSM (Single-SIM) or XT1033 - Retail Asia (Dual-SIM) 
CID9 = XT1031 - CDMA (Boost US) or XT1032 - Retail US Global GSM or XT1034 - Retail US AWS
CID12 = XT1032 - Latin America / Brazil Global GSM (Single-SIM) or XT1033 - Latin America / Brazil Global GSM (Dual-SIM) 
CID14 = XT1034 - Retail Canada AWS or XT1034 - Bell Canada AWS

IMEI

IMEI=$(cat /proc/config/imei/ascii)
echo 'AT+EGMR=1,9,'"$IMEI" > /dev/pttycmd1

Commands

List all files:

ls -lRa

Remount file system as read/write:

mount -o remount,rw /system

Symbolic Link:

ln -sf /system/efs

Change modes:

chmod 0555 filename