Checking disk space from the command-line

Josh Sherman
3 min read
Command-line Interface

As you may already be aware, I also write guides for As of late, I’ve been covering a lot of command-line tools and tricks as part of a “Command-line Basics” series.

I’m also a bit of a scatter brain sometimes, and last month ended up starting on this particular blog post, realizing about half way through that I had already written a post on analyzing disk usage.

I had stashed the post in my home directory as I didn’t necessarily want to throw away something I put some effort into. Today as I struggled to come up with a topic for my blog this week, I happened upon the file and figured it’s day has come!

Without further ado…

The moment your system runs out of persistent storage (a/k/a disk space) things can go off the rails quite quickly. Applications begin to behave erratically and you can forget about saving whatever you’re working on. Things are even worse on a remote server since there’s no GUI to growl at you about it. As per usual, the command-line has you covered when you need to check what your current disk usage is looking like.

Getting started

For this post we’re going to be using the commands df and du. Both are pretty standard issue on Unix-like operating systems such as Linux and macOS.

To find out if you have them available, simply try running them.

On the off chance you don’t have these commands available, please consult with your system’s package manager to see about remedying the situation. If you happen to have a remote server available, you can always SSH in and follow along at home.

None of the commands in this post are destructive in nature.

Checking total and available disk space

The quickest and easiest way to check your the total size, usage and availability of all of your mounted disks is to run df without any arguments.

$ df
Filesystem     1K-blocks      Used Available Use% Mounted on
dev             16398928         0  16398928   0% /dev
run             16407640      1688  16405952   1% /run
/dev/nvme0n1p2 982940416 234606476 698333592  26% /
tmpfs           16407640    791960  15615680   5% /dev/shm
tmpfs           16407640         0  16407640   0% /sys/fs/cgroup
/dev/nvme0n1p1    523248    108564    414684  21% /boot
tmpfs           16407640      7468  16400172   1% /tmp
tmpfs            3281528        68   3281460   1% /run/user/1000

Without any arguments, df shows the size in 1K blocks (1024) not to be confused with 1kB blocks (1000).

Those large numbers can be intimidating, but at the very least, we can easily grok what percentage of the disk has been used, and the current mount point.

To corral those blocks a bit, we can pass in the -h or --human-readable argument to display the sizes in the power of 1024.

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
dev              16G     0   16G   0% /dev
run              16G  1.7M   16G   1% /run
/dev/nvme0n1p2  938G  224G  666G  26% /
tmpfs            16G  786M   15G   5% /dev/shm
tmpfs            16G     0   16G   0% /sys/fs/cgroup
/dev/nvme0n1p1  511M  107M  405M  21% /boot
tmpfs            16G  7.3M   16G   1% /tmp
tmpfs           3.2G   68K  3.2G   1% /run/user/1000

Much easier to understand at a glance!

I take things a step further by aliasing df to df -h so I never have to worry about passing in the argument:

alias df='df -h'

Checking disk usage of a particular directory

Finding the total disk…

And that’s when the light bulb went off and I started to feel like I had written this post already. The section that was left unfinished was going to cover using du, which you can read about over on the original post.

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