When working with Windows Subsystem for Linux (WSL), you might notice that changes to your Windows hosts file (%WINDIR%\System32\drivers\etc\hosts) don't automatically propagate to WSL's /etc/hosts. This happens because:

• WSL only reads the Windows hosts file during initial startup
• The copy is cached for the WSL instance's lifetime
• Simply closing and reopening terminals doesn't trigger a refresh

Method 1: Restarting the WSL Instance

The most reliable way is to completely restart your WSL instance:

wsl --shutdown
wsl

This terminates all WSL instances and creates a fresh one with updated hosts.

Method 2: Using a Custom Script

For frequent updates, create a bash script:

#!/bin/bash
# Force update WSL hosts file
sudo cp /mnt/c/Windows/System32/drivers/etc/hosts /etc/hosts
sudo chmod 644 /etc/hosts
sudo service networking restart

Save as update-hosts.sh and make it executable with chmod +x update-hosts.sh.

Method 3: Automating the Process

For developers who frequently modify hosts, consider this PowerShell automation:

# PowerShell script to watch for hosts file changes
$watcher = New-Object System.IO.FileSystemWatcher
$watcher.Path = "C:\Windows\System32\drivers\etc"
$watcher.Filter = "hosts"
$watcher.NotifyFilter = [System.IO.NotifyFilters]::LastWrite

Register-ObjectEvent $watcher "Changed" -Action {
    wsl --shutdown
    wsl
}

For those running multiple WSL distributions:

wsl --shutdown
wsl -d Ubuntu-20.04
wsl -d Debian

Remember that each distribution maintains its own /etc/hosts copy.

A full Windows reboot achieves the same result as wsl --shutdown because:

• All WSL instances are terminated during shutdown
• The fresh start reads the current Windows hosts file
• No cached versions remain in memory

---

When working with Windows Subsystem for Linux (WSL), you might notice that the /etc/hosts file gets automatically populated from the Windows host file (%WINDIR%\System32\drivers\etc\hosts) during the first WSL instance launch. However, subsequent modifications to the Windows hosts file don't automatically propagate to WSL.

The current behavior requires either:

• A full Windows system reboot
• Completely shutting down all WSL instances and restarting

This can be particularly frustrating during development when you're:

• Testing local domain configurations
• Working with containerized environments
• Developing microservices with custom host entries

Here are three reliable methods to force a refresh:

Method 1: Full WSL Shutdown

Run these commands in PowerShell:

wsl --shutdown
wsl

This completely terminates all WSL instances and forces a fresh initialization.

Method 2: Temporary File Replacement

Create a script in your WSL instance:

#!/bin/bash
sudo cp /dev/null /etc/hosts
sudo wsl.exe -d "$(wsl.exe -l | head -n 2 | tail -n 1 | awk '{print $1}')" -u root -e cp /etc/hosts /etc/hosts.bak
sudo wsl.exe -d "$(wsl.exe -l | head -n 2 | tail -n 1 | awk '{print $1}')" -u root -e cp /mnt/c/Windows/System32/drivers/etc/hosts /etc/hosts

Method 3: Using wsl.conf (Permanent Solution)

Create or modify /etc/wsl.conf:

[network]
generateHosts = false

Then manually copy your Windows hosts file:

sudo cp /mnt/c/Windows/System32/drivers/etc/hosts /etc/hosts

For frequent updates, create a PowerShell function:

function Update-WslHosts {
    wsl --shutdown
    wsl -d Ubuntu-20.04 -- sudo cp /mnt/c/Windows/System32/drivers/etc/hosts /etc/hosts
}

After refreshing, verify the changes with:

cat /etc/hosts

Or test specific entries with:

ping mylocal.dev