What does this line "/dev/sda5: clean, 956436/30277632 files, 37421846/121093120 blocs" mean while booting? [duplicate]

After I upgraded my Ubuntu from 14.04 to 16.04, I am getting a weird line on my screen each time I power on my laptop:

/dev/sda5: clean, 956436/30277632 files, 37421826/123093120 blocks

What does this line mean?

I worry about the meaning of the numbers, because the first number says that some files were cleaned, and the second one says that some files were blocks...

Nothing special or complicated, just for general understanding.

It's a harmless message, rather a good news for you!!

While booting, by default, the root filesystem (filesystem containing mount point /), is gone through a filesystem check using fsck, this is the result of that check. If there were any error the filesystem would be mounted read only, rather than read-write.

Although this an assumption from my side, to be precise this is the fsck output for the filesystem created on partition /dev/sda5, as you can do fsck on any disk backed filesystem but by default fsck is not done on filesystems other than the one having the root directory as mount point.

About the blocks, the filesystem divides the while partition into blocks, blocks are the minimal operational unit (so also the storage unit) to a filesystem. While writing, filesystem writes in full blocks i.e. if a file's actual size is 200 Bytes, it will take a block size space in the filesystem, hence on the underlying disk. For ext4, the block size is 4 KB.

In the message:

956436/30277632 files, 37421826/123093120 blocks

956436 is the number of inodes used from a total of 30277632(fixed at the time of filesystem creation), same goes for the blocks usage numbers.

Here "clean" after the partition means the partition is allright, there is no issue with it.