By the end of this lesson you will be able to
- Explain what a file system is using an everyday comparison.
- Name ext4, NTFS, FAT32 and exFAT and say where each is used.
- Choose a suitable file system for a USB stick used on several systems.
- Explain why a program for one operating system may not run on another.
- List at least three ways to get a job done when software is not available for your system.
Two common frustrations have the same root cause. A USB stick works on one computer and not on another. A program your friend uses will not install on your laptop. Both are about compatibility: whether two things were built to understand each other. Once you know the reasons, you can choose the right option instead of guessing.
What a file system is
A drive is just a long row of tiny storage cells. Without organisation, nobody could find where one file ends and another begins. A file system is the system of organisation: it decides how names, folders, sizes and dates are recorded, and where on the drive each file's data sits. Think of a library. The books are the data. The catalogue, the shelf labels and the numbering scheme are the file system. Without them the books are still there but nobody can find anything.
Different operating systems favour different catalogues. A computer can read a drive only if it understands the catalogue on it. A drive that has none, or one the computer does not know, may show up as unreadable or ask to be formatted. Formatting sets up a new, empty catalogue, and it erases everything that was on the drive.
- Data exists
- No names or folders
- Nothing can be found
Unusable until formatted.
- Files have names and places
- Folders keep order
- Quick to find
Ready to use.
Read this figure as text
A compare diagram of a drive with and without a file system, using a library comparison.
Without a file system: the drive holds data, but nothing records which data belongs to which file, like books piled on the floor with no catalogue. With a file system: each file has a name, a place, a size and a date, folders organise them and the computer finds them quickly, like a library with labelled shelves and a catalogue.
The file systems you will meet
| File system | Main use | Works with | Watch out for |
|---|---|---|---|
| ext4 | Ubuntu and many Linux systems' main drive | Linux. Windows cannot read it without extra software. | Not suitable for a USB stick that you share with Windows users. |
| NTFS | Windows' main drive | Windows fully. Ubuntu can read and write it. Some devices cannot. | Cameras, TVs and some consoles may not accept it. |
| FAT32 | Older USB sticks, memory cards, some devices | Almost everything. | A single file cannot be larger than 4 GB. |
| exFAT | Large USB sticks and cards, sharing between systems | Windows, Ubuntu, macOS and many cameras. | Designed for removable drives, not the main system drive. |
- ext4Linux main drive. Not read by plain Windows.
- NTFSWindows main drive. Ubuntu reads and writes it.
- FAT32Works almost anywhere. 4 GB file limit.
- exFATWorks on Windows, Ubuntu and macOS. Good for sharing.
Read this figure as text
A set of four cards summarising ext4, NTFS, FAT32 and exFAT and where each works.
ext4: best on Linux, not readable on a plain Windows laptop. NTFS: best on Windows, readable and writable on Ubuntu, not on every device. FAT32: works nearly everywhere but a file cannot exceed 4 GB. exFAT: works on Windows, Ubuntu, macOS and many devices, and has no 4 GB limit, so it is the usual choice for a shared USB stick.
Finding out which file system a drive uses
Look, do not change
Ubuntu: Disks
Step 1: Open Disks
Open Activities, type
Disksand press Enter. It is a tool for viewing drives.You should see: A window opens with a list of drives on the left.
Step 2: Choose a drive
Click a drive in the left list. Look at the large block that appears in the main part of the window and click it.
You should see: Details appear below, including Contents, which names the file system, for example Ext4 or FAT.
Step 3: Leave it alone
Do not click the buttons marked with a gear or minus. Close the window when you have read the type.
You should see: Nothing has changed.
Windows: File Explorer
Step 1: Open This PC
Open File Explorer from the taskbar and click This PC in the left list.
You should see: Your drives are shown, such as Local Disk (C:).
Step 2: Open Properties
Right-click a drive and choose Properties. Stay on the General tab.
You should see: A small window shows File system, for example NTFS or exFAT, and the used and free space.
Step 3: Close without changing
Click Cancel or close the window.
You should see: Nothing has changed.
Name: Practice stick
File system: exFAT
Used 2.1 GB, free 29.9 GB
- Marker 1: The file system type
- Marker 2: Used and free space
- Marker 3: Close without changing anything
Read this figure as text
A simulated properties dialog for a drive, showing File system and free space with a Cancel button.
A simulated dialog titled Drive properties. A line says Name: Practice stick. A second line says File system: exFAT, marker 1. A third line says Used space 2.1 GB and Free space 29.9 GB, marker 2. A Cancel button at the bottom, marker 3, closes the window without changing anything. Real tools word these slightly differently.
So if you will use one USB stick on both Ubuntu and Windows, exFAT is normally the right choice. If a file is larger than 4 GB, avoid FAT32. If a stick is read-only on one computer or not recognised at all, check its file system first.
Why programs do not run everywhere
A program is a set of instructions built for one operating system. It makes requests that only that system understands, and it comes in a file format that only that system knows how to open. A Windows program often has the extension .exe or .msi. Ubuntu cannot normally run it. Ubuntu programs arrive from the App Center, as Debian packages with a .deb extension, or as Snap or Flatpak packages. Windows cannot run those either. This is not a fault. It is the same as an English book on a shelf of French readers.
- Files end in .exe or .msi
- Installed by Setup or the Microsoft Store
- Speak to Windows
Run on Windows.
- From App Center, .deb, Snap or Flatpak
- Installed through the App Center
- Speak to Linux
Run on Ubuntu and other Linux.
Read this figure as text
A compare diagram of a Windows program and an Ubuntu program, each fitting only its own system.
Windows program: file names often end in dot exe or dot msi, installed through Setup or the Microsoft Store, runs on Windows. Ubuntu program: comes from App Center, or as a dot deb, Snap or Flatpak package, runs on Ubuntu and many other Linux systems. Each speaks to its own operating system and does not work on the other without a translator or a different version.
What to do when the program you want is not available
- Look for a version for your system. Many popular programs, such as browsers, media players and LibreOffice, exist for Windows, Linux and macOS.
- Use an alternative. Ubuntu offers LibreOffice for documents, GIMP for pictures and Firefox for browsing. Files can often be shared between them.
- Use a {{web-app|web app}}. Many programs now run inside the browser, so they work on any system. This is the easiest route to compatibility.
- Try a {{compatibility-layer|compatibility layer}}. A tool called Wine lets some Windows programs run on Linux. It does not work for everything, can be fiddly and is for later, not for beginners.
- Use a computer with the right system. For a program that is essential, such as a work tool, a Windows computer may be the right answer. Check what you need before buying.
- Is there a version for your system?
- YesDo thisInstall it from the App Center or the maker's official site.
- NoIs there an alternative that opens the same files?
- YesDo thisUse the alternative, for example LibreOffice for documents.
- NoIs there a web version?
- YesDo thisUse it in your browser. It works on any system.
- NoDo thisYou may need a computer with the right system. A compatibility layer such as Wine is an advanced option that does not always work.
Read this figure as text
A yes or no decision tree that ends in a native version, an alternative, a web app or a Windows computer.
Start: does the program have a version for your system? If yes, install that version from the App Center or the maker's official site. If no: is there a good alternative that opens the same files? If yes, use it. If no: does the program have a web version? If yes, use it in your browser. If no, you may need a computer with the right operating system, or to ask whether a compatibility layer is suitable.
Common mistakes
✖ Instead of: Clicking Format when a drive shows as unreadable, to see if it fixes it.
✔ Do this: Formatting erases the drive. Check the file system first, try another computer, and copy anything important off before formatting.
✖ Instead of: Pulling out a USB stick without ejecting it.
✔ Do this: Eject it first. The system may still be writing data, and pulling it out can damage files.
✖ Instead of: Downloading a free copy of a paid Windows program to try on Ubuntu.
✔ Do this: Such files often carry malware. Use official sources and legitimate alternatives.
✖ Instead of: Assuming a 4 GB file will fit on any stick that has enough space.
✔ Do this: A FAT32 stick cannot hold a file bigger than 4 GB, however much space is free. Use exFAT.
If something goes wrong
- A USB stick does not appear in Files or File Explorer.
- Try another port, then another computer. Check in Disks (Ubuntu) or Disk Management (Windows) whether it appears there. If it appears with an unknown file system, do not format it unless it holds nothing you need.
- A stick is read-only on one computer.
- It may have been unplugged without ejecting, or have a physical lock switch. Check for a switch, then eject properly and try again. Copy files to your computer if you need to edit them.
- Copying a large file to a stick fails with a message about file size.
- The stick is probably FAT32. Copy the stick's files elsewhere, then format it as exFAT only if it has nothing else you need.
- A downloaded program will not open on Ubuntu.
- Check the extension. A .exe or .msi is for Windows. Look in the App Center for a version for Ubuntu, or use an alternative or a web app.
Key terms
- File system
- The way a drive organises and keeps track of files and folders.
- ext4
- The standard file system that Ubuntu and many other Linux systems use on their main drive.
- NTFS
- The standard file system that Windows uses on its main drive.
- exFAT
- A simple file system that Windows, Ubuntu, macOS and many cameras can all read and write, with no small file size limit.
- FAT32
- An old, very widely understood file system that cannot hold a single file larger than 4 GB.
- Formatting
- Preparing a drive with a file system, which erases everything that was on it.
- Web app
- A program you use inside a web browser, so it works on any computer with a browser and an internet connection.
- Compatibility layer
- Software that lets programs made for one operating system try to run on another, though not always perfectly.
Practise it for real
Reading is not the same as being able to do it. Complete these on your own computer, then tick only what you have actually done. These ticks are your own honest record: nothing checks them for you.
Find the file system of two drives
Use Disks (Ubuntu) or File Explorer properties (Windows) to find the file system of your laptop's main drive. If you have a USB stick, plug it in and find its file system too. Write down both. Do not format, repartition or change anything. Safely remove the stick afterwards by right-clicking it in the file manager and choosing Eject (Ubuntu) or Eject (Windows) before you pull it out.
Challenge: plan for an unavailable program
Choose a program you have heard of that only runs on Windows (a friend or a job advert may mention one). Use the decision path from this lesson to write what you would do on Ubuntu: look for a native version, an alternative, a web version or another computer. Name your choice and the first step. Use only the maker's official sites for your research.
Knowledge check
6 questions. You need 80% to pass. Mistakes here are part of learning, and you can retry as often as you like.
Summary
- A file system is the catalogue that lets an operating system find files on a drive.
- ext4 is usual on Ubuntu, NTFS on Windows, and exFAT is the best choice for a stick shared between systems.
- FAT32 works nearly everywhere but cannot hold a file larger than 4 GB.
- Formatting erases everything on a drive.
- Programs are built for one operating system. Use a native version, an alternative, a web app or the right computer.
Checklist: can you do these?
Marking a lesson as read does not prove you can do it. Skills count as demonstrated when you pass the quiz (not yet) and complete the practical tasks (not yet).
Related lessons
References and further reading
Official sources for details that can change between versions.
- Ubuntu Desktop help (Ubuntu)
- Windows help and learning (Microsoft)