As an administrator, you will also need to keep track of available disk space on your
disks. So let's have a look at the commands that are involved. To start with, there is
the df command. Df shows the amount of space that is available on mounted devices. It has
different options to determine how you want to see it displayed. Then there is du, which
stands for disk usage. It's giving a summary, and the nice thing about it is that you can
see how much files you've got in a specific directory. Now, you should notice that these
utilities don't work very well on thin provisioned storage, and that is because thin provisioned
storage is pretending to offer more storage than is really available. So you might see
20 GB available, where in reality, after writing 5 GB, your thin provisioned storage might
be full. Let me demonstrate these tools. So let's use df –h to start with. I like
the option –h, because –h is giving a human-readable format. So here we can see
the most important storage device, which is the LVM Logical Volume Root on the volume
group CS, and it has 13 GB available. Otherwise, we can see that there is the boot device with
606 MB available. I just said gigabyte. Really, it's gibibyte, because gibi, mebi, and so on
is the default display in anything regarding your storage. Now, if you want to see how much
files in a directory, use du –hs on USR, for instance. Then it needs to calculate a little
bit, and here we can see that USR in total has 3.8 GB of storage available. And that's
how you monitor available disk space.