Push command not working says permission denied I rooted my micromax p275 and wanted to change its font by replacing /system/fonts/Roboto-Regular.ttf with my desired font but i accidentally replaced it with Robot.Regular.ttf.  Now it doesn't starts. 
  I want to push another font file in /system/fonts with the correct name (Roboto-Regular.ttf)  but it doesn't works saying permission denied. I have tried su command  but it just reprints the same commands i type and press enter and thus doing nothing. Any way out friends. I would be greatly helped by you. Every single hint is wanted.
If you have a backup font file and adb is working, then you can just do adb remount and try pushing the backup font again. This command is just a shortcut for adb shell mount -o remount.rw /system, which remounts /system as writable.

If adb remount doesn't work, then run adb root and try again. (i.e., run adb root, adb remount, and adb push /path/to/backup/Roboto-Regular.ttf /system/fonts/, in that order). I'm not sure how picky adb is about telling it to use root.