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Fix WSL Path Error: Invalid Character & Colon in Files

Struggling with 'Invalid character' or colon errors in your WSL path? Learn the permanent fix using wsl.conf metadata and other quick workarounds. Tame your WSL!

Alex Carter

A DevOps engineer and technical writer passionate about cross-platform development and automation.

September 12, 20256 min read13 views

You’re in the zone. Firing on all cylinders, deep inside your Windows Subsystem for Linux (WSL) terminal. You go to clone a repository, unzip an archive from a colleague, or run a script that generates timestamped files. And then... BAM.

tar: 'backup-2025-01-15T10:30:00.log': Cannot open: Invalid argument

Or maybe you see a cryptic Function not implemented or a simple Invalid character in path. You stare at the screen, then at the filename. And there it is, mocking you: a colon (:). Or maybe it's a question mark, or an asterisk. What gives? You thought WSL was your seamless bridge between the worlds of Windows and Linux.

Don't worry, it still is. This is one of the most common—and most frustrating—hiccups WSL users encounter. The good news is that it’s not just fixable; it’s understandable. Let's dive in and fix this for good.

A Tale of Two Filesystems

The root of this problem lies in a fundamental difference between how Linux and Windows think about filenames. It’s a classic case of lost in translation.

Your main Linux environment within WSL (the one you get to by typing cd ~) typically runs on a filesystem like Ext4. This filesystem is incredibly flexible. It happily accepts filenames containing a wide variety of characters, including the infamous colon. This is why a file named report:final-draft.docx is perfectly normal on Linux or macOS.

Windows, on the other hand, uses the NTFS filesystem. NTFS has a stricter set of rules. For historical and system-level reasons, it reserves certain characters for special functions. The colon, for example, is sacred—it’s used to denote drive letters (C:) and more obscure things like Alternate Data Streams.

Here’s the list of forbidden characters in Windows filenames:

< > : " / \ | ? *

When you work within a mounted Windows drive in WSL (like your C: drive, which appears as /mnt/c/), you're not actually on the Linux filesystem anymore. You're asking Linux to write a file directly onto the NTFS partition. When Linux tries to create a file named log:123.txt on /mnt/c/Users/YourUser/Documents, Windows throws its hands up and tells WSL, "I can't do that," resulting in the "Invalid argument" error.

The Permanent Fix: Unleash WSL Metadata

For a long time, the only solution was to manually rename files. Thankfully, the WSL team provided a powerful, permanent solution: metadata support. This is the fix you should implement today.

What is WSL Metadata?

In simple terms, enabling metadata on your Windows mounts tells WSL to get creative. When it encounters a file with a character that’s illegal in Windows (like a colon), it doesn't try to write the colon directly. Instead, it saves the file with a Windows-compliant name and stores the "real" Linux name, including the special characters and permissions (like chmod/chown), as extra data attached to the file.

To you, inside WSL, the file looks completely normal: ls will show backup-2025-01-15T10:30:00.log. But to Windows File Explorer, the file might look slightly different, with the illegal characters encoded. This is the magic bridge that lets both systems coexist peacefully.

Step-by-Step: Enabling Metadata in wsl.conf

Ready to apply the fix? It only takes a minute.

Open Your WSL Terminal
Launch your favorite WSL distribution (Ubuntu, Debian, etc.).
Edit the WSL Configuration File
This file, /etc/wsl.conf, controls how WSL behaves. If it doesn't exist, this command will create it. We'll use the simple `nano` editor, but feel free to use `vim` or your editor of choice.
```
sudo nano /etc/wsl.conf
```
Add the Metadata Option
Add the following lines to the file. If the file already has an [automount] section, just add the options line to it.
```
[automount]
options = "metadata"
```
Your file should look exactly like that. This tells WSL to enable the metadata feature for all automatically mounted Windows drives (like C: and D:).
Save and Exit
In `nano`, press Ctrl+X, then Y to confirm you want to save, and finally Enter to accept the filename.
THE CRUCIAL STEP: Restart WSL
This change will not take effect until WSL is fully shut down. Simply closing the terminal window is not enough. You must open PowerShell or Command Prompt and run:
```
wsl --shutdown
```
This command terminates all running distributions and the WSL 2 lightweight VM. It will restart automatically the next time you open your WSL terminal.

And that's it! The next time you open your WSL terminal, navigate to a Windows directory (e.g., cd /mnt/c/Users/) and try to create a file with a colon. It will work flawlessly.

# This will now work!
touch /mnt/c/Users/YourUser/Desktop/file:with:colons.txt

Alternative Solutions & Quick Fixes

While the wsl.conf metadata fix is the best all-around solution, it’s good to have a few other tricks up your sleeve for situations where you can't or don't want to change the configuration.

On-the-Fly Transformation with `tar`

A common source of this error is extracting a .tar archive created on a Linux or macOS system. The tar command has a fantastic, underused feature called --transform that can solve this problem on the fly.

Let's say you have archive.tar.gz full of files with colons. You can extract it while replacing all colons with underscores like this:

tar -xvf archive.tar.gz --transform='s/:/_/g'

This command uses a regular expression to substitute (s) every colon (:) with an underscore (_) globally (g) for every filename it extracts. The original archive remains untouched.

The "Stay in Your Lane" Approach

For performance and compatibility, one of the best practices with WSL is to do your heavy lifting inside the native Linux filesystem. Clone your git repositories, run your build processes, and manage your containers in your Linux home directory (~).

In this workflow:

Do all your work in ~/projects/my-repo. Filenames with colons are fine here.
When you have a final artifact or file you need to access from Windows, copy it to a mounted drive like /mnt/c/Users/YourUser/Documents/.
If that final file has an illegal name, rename it before or during the copy.

This avoids the path translation issue entirely for your day-to-day work and often results in significantly faster file operations.

Conclusion: No More Path Headaches

That pesky "Invalid argument" error is more than just a minor annoyance; it’s a crack in the seamless experience WSL promises. But by understanding the simple conflict between Linux and Windows filesystem rules, you can easily patch it up.

For 99% of users, editing /etc/wsl.conf to enable metadata is the definitive, set-and-forget solution. It bridges the gap, allowing you to work with Linux-style filenames on your Windows drives without a second thought. For those one-off situations, keeping tools like tar --transform in your back pocket makes you a more versatile command-line navigator.

Now, go forth and conquer your command line—colons, question marks, and all. They hold no power over you anymore.