If you try to create any folder or push any file using ADB to android file systems like /system and if it is mounted as Read-Only then it may shows error code like “failed to copy files to ‘/system/lib//cfg80211.ko’: Read-only file system. In this case you nee,d to remount it as Read-Write(RW). Below are the commands for this.

$mount -o rw,remount /system  • For remounting root, //will be used for pushing init.rc files in /root $ mount -o rw,remount /

$mount -o ro,remount /system  • Or you can use adb tool to remount it as R/W $ adb remount