This article is from the Frequently Asked Questions for Linux, the Free/Open Source UNIX-like operating system kernel that runs on many modern computer systems. Maintained by David C. Merrill with numerous contributions by others. (v1.0).
A: To understand how you got into this state, see EXT2-fs: warning: mounting unchecked file system.
Remount it. If /etc/fstab is correct, you can simply type:
mount -n -o remount /
If /etc/fstab is wrong, you must give the device name and possibly the type, too: e.g.
mount -n -o remount -t ext2 /dev/hda2 /