# What's Filling My Disk? du and df du shows how much disk space each file and folder takes, sort -h puts those sizes in order with the biggest first, and df shows how much room is left on the drive. Apprentice · Unix · Linux · Updated November 10, 2026 ## After this lesson you can - Find what takes the most space in a folder with du -sh, sorted biggest first with sort -h - Check how much room is left on a drive with df -h ## Key takeaways - du -sh and a name shows how much space a file or folder takes. du -sh * does it for everything in the folder you're in. - The | (pipe) hands one command's output to the next one: du -sh * | sort -hr lists the biggest first. - sort -h understands sizes such as 28K and 3.9M. Plain sort reads them as text and gets the order wrong. - df -h shows a drive's size, how much of it is used and how much is left. df -h . shows only the drive you're working on. - du and df only read sizes, so they're safe to run on any folder. It's the night before a trip, you want to download a few movies for the flight, and your laptop says the disk is almost full. Something is taking up the space, but what? A file manager makes you open folder after folder and check each one's size by hand. The terminal answers in one line: `du` says what takes the space, and `df` says how much is left. IT help-desk techs ask exactly this on a full laptop, and web developers ask it when a server stops saving files because its disk filled up. ## Set up a packing folder The lessons in this chapter use a made-up folder of things for a summer trip: photos, a video, some music and the travel papers. Copy these lines into your terminal. They make the folder `~/terminal-practice/packing`, fill it with stand-in files, and list what's there. They're safe to run again. ```bash mkdir -p ~/terminal-practice/packing && cd ~/terminal-practice/packing mkdir -p photos/beach photos/city videos music documents/2026/summer-trip/tickets printf 'passport\nphone charger\nsunscreen\nheadphones\n' > packing-list.txt head -c 2500000 /dev/urandom > photos/beach/sunset.jpg head -c 2100000 /dev/urandom > photos/beach/waves.jpg head -c 1800000 /dev/urandom > photos/city/museum.jpg head -c 1600000 /dev/urandom > photos/city/street-food.jpg head -c 15000000 /dev/urandom > videos/drone-flight.mp4 head -c 4000000 /dev/urandom > music/road-trip-mix.mp3 printf 'Flight to Lisbon, June 12, seat 14C\n' > documents/2026/summer-trip/tickets/flight.txt printf 'Train to Porto, June 15, coach 4\n' > documents/2026/summer-trip/tickets/train.txt printf 'Hotel Sol, June 12 to 15, booking 4471\n' > documents/2026/summer-trip/hotel.txt ls ``` ```text documents music packing-list.txt photos videos ``` The `head -c` lines give each stand-in photo and video a real size. `/dev/urandom` is an endless supply of random bytes that Linux and macOS both have; `head -c 2500000` takes the first 2,500,000 of them (`-c` counts bytes, where plain `head` counts lines), and `>` saves them as the file. ## du: how much space does it take? `du` stands for *disk usage*. Give it `-s` (for *summary*: one total, not every folder inside), `-h` (for *human-readable*, the same `-h` as in `ls -lh`) and a folder's name: ```bash du -sh photos ``` ```text 7.7M photos ``` The four photos take 7.7 megabytes. To see everything in the folder at once, use `*` (read "star"), which stands for every name here, as in *Wildcards: \*, ? and [ ]*: ```bash du -sh * ``` ```text 28K documents 3.9M music 4.0K packing-list.txt 7.7M photos 15M videos ``` One line per name, size first. Two things look odd at first. `packing-list.txt` holds only 44 bytes, yet du says 4.0K: a disk hands out space in blocks, usually 4 kilobytes each, and even a tiny file takes a whole block. And the list is in alphabetical order, so in a folder of 200 names the big one could be anywhere. ## Biggest first: sort -h and a first pipe The fix is to hand du's list to `sort`, which puts lines in order. The `|` between them (read "pipe") works like the pass in a restaurant kitchen: one cook sets a finished plate on it, and the next cook picks it up. du's lines go to `sort` instead of to the screen: ```bash du -sh * | sort -h ``` ```text 4.0K packing-list.txt 28K documents 3.9M music 7.7M photos 15M videos ``` `-h` tells `sort` to read sizes the human way, so K comes before M, and M before G. Add `-r` (for *reverse*) to put the biggest first: ```bash du -sh * | sort -hr ``` ```text 15M videos 7.7M photos 3.9M music 28K documents 4.0K packing-list.txt ``` There's the answer: one video takes more space than all four photos together. Leave out the `-h` and `sort` compares the sizes as text, character by character, so `15M` lands above `28K` because 1 comes before 2. Pipes can do a lot more than this; *Pipes: |*, in Module 3, takes them apart. To look one level deeper, leave out `-s`. du then lists every folder inside, with the total last: ```bash du -h photos ``` ```text 3.3M photos/city 4.4M photos/beach 7.7M photos ``` ## df: how much room is left? du measures what's in your folders; `df` (*disk free*) measures the drive itself. `df -h .` reports on the drive that holds the folder you're in (`.` is "this folder"): ```bash df -h . ``` ```text Filesystem Size Used Avail Use% Mounted on /dev/sdd 1007G 30G 926G 4% / ``` Your numbers and names will be different. Read the line left to right: the drive's name, its size, how much is used, how much is available, the used part as a percentage, and the folder where it appears ("mounted on"). Linux calls each of these a **file system**: a drive, or part of one, set up to hold files. A "disk almost full" warning means Use% is close to 100%. On its own, `df -h` lists every file system, including small ones the system keeps for itself, so expect a long list. In WSL it also shows your Windows drives, such as `C:\` mounted on `/mnt/c`. On a Mac, the volume that holds your files is usually the one mounted on `/System/Volumes/Data`; `du -sh` and `sort -h` work the same there. du and df only read sizes; they never move or delete anything. So try them on your real files: `du -sh ~/* | sort -hr` lists everything in your home folder, biggest first. On a big home folder it can take a moment. ## Check yourself 2 questions to try on the lesson page. ## So what "Disk almost full" stops being a mystery: `du -sh * | sort -hr` points straight at what's taking the space, and `df -h` tells you how much room you've won back. ## Key terms - [df and du](https://www.ask-codey.com/glossary/df-and-du) - [Pipe](https://www.ask-codey.com/glossary/pipe-unix) - [File System](https://www.ask-codey.com/glossary/file-system) ## Cheat sheets - [What's Filling My Disk? du and df](https://www.ask-codey.com/cheat-sheets/bash-disk-space-cheat-sheet) ## Related - [Looking Around: ls](https://www.ask-codey.com/lessons/bash-looking-around) - [Shortcuts to Files: ln -s](https://www.ask-codey.com/lessons/bash-symbolic-links) - [Many Files as One: tar and zip](https://www.ask-codey.com/lessons/bash-archives) Source: https://www.ask-codey.com/lessons/bash-disk-space