Recently I've seen the root filesystem of a machine in a remote datacenter get remounted read-only, as a result of consistency issues.
On reboot, this error was shown:
UNEXPECTED INCONSISTENCY: RUN fsck MANUALLY (i.e., without -a or -p options)
After running fsck as suggested, and accepting the corrections manually with Y, the errors were corrected and the system is now fine.
Now, I think that it would be interesting if fsck was configured to run and repair everything automatically, since the only alternative in some cases (like this one) is going in person to the remote datacenter and attach a console to the affected machine.
My question is: why does fsck by default ask for manual intervention? How and when a correction performed by such program would be unsafe? Which are the cases when the sysadmin might want to leave a suggested correction aside for some time (to perform some other operations) or abort it alltogether?