Differences between du and df

Issue link

You will certainly ask yourself one day: “What is the difference between the du command and the df command?”

According to the man page for du:

  du - estimate file space usage
  

And df displays exactly the space taken on your hard drive. I encountered a case where on a 30 GB partition, I had this:

  du -sh | grep /home : 13 G used
df -h /home : 26 G used
  

The df command is not wrong.

Solutions link

Check the number and size of blocks on your partition link

Indeed, when formatting your partition, you can choose the block size. By default it’s 8KB. This means that if you have many files of just a few bytes, they will still take up 8KB each.

The only solution is to backup your data, reformat with a much smaller block size, and then restore the backup.

Check processes that are writing to this partition link

It can happen that processes that were writing to the partition have crashed. In this case, the size remains in virtual memory and that’s when problems occur. So analyze your partition:

  lsof /home
  

and check the running processes:

  ps -aux