Ubuntu - How to change the file system from read-only to read-write in safe mode

Environment
  • Ubuntu 12.04

Content
When in safe mode, the file system was read-only, and I had to edit some files in "/usr/share/pam-configs/". How the file system was changed to be read-write. From askubuntu.com, it can be by remounting.
#mount -o remount,rw /