Errors in a filesystem can prevent a system from booting properly and are commonly caused by improper system shutdown. The fsck (filesystem check) utility can identify and repair errors.
To check and interactively repair filesystem errors on the device c0t0d0s1, run the following command as root:
Be careful when specifying the path to the device. There are two links to the same physical device, one in /dev/dsk and the other in /dev/rdsk. The rdsk represents the media as a raw device which is appropriate for low-level operations such as fsck and newfs. The dsk represents a cooked filesystem that is appropriate for mounting and other high-level operations.