This message comes at boot time from the /etc/rcS script whenever it gets a bad return code from fsck(1M) after checking a file system. The message recommends an fsck(1M) command line, and instructs you to exit the shell when done to continue booting. Then the script places the system in single-user mode so fsck(1M) can be run effectively.
For information about repairing UFS file systems, refer to "/dev/rdsk/string: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.".
For information about repairing non-UFS file systems, refer to "THE FOLLOWING FILE SYSTEM(S) HAD AN UNEXPECTED INCONSISTENCY:".