Sometimes when you boot Ubuntu you can see this error:
(Initramfs): /dev/sda1 contains a file system with errors, check forced. Inodes that were a part of a corrupted orphan linked lost found. /dev/sda1 : UNEXPECTED INCONSISTENCY; RUN fsck manually.(I.e ., without -a or -p options). fsck exited with status code 4. The root filesystem on /dev/sda1 requires a manual fsck
Solution:
From there, you should be able to drop to some maintenance shell (if not already opened), where you may run fsck -yf /dev/sda1.
If there are any errors rerun fsck -yf /dev/sda1
To login as usual simply run exit and proceed normally.