Cross-Platform File Sharing with SMB

If you possess multiple computers and operating systems, say a Macbook for MacOS applications, a Windows PC for gaming, and a Linux PC or virtual machine for work, moving files between them quickly becomes a headache. You could use a USB drive with exFAT file system format but most USB drives are limited in capacity. You could also use cloud storage but it adds latency and a third-party dependency for files that never need to leave your home network. The most reliable and scalable solution is to buy a dedicated NAS if you have a few hundred dollars to spare, or you could set up your own file sharing system for free.

Introducing SMB (Server Message Block): it is a network file-sharing protocol supported natively by macOS, Windows, and Linux that lets every device on your local network access shared folders as if they were local drives — no format compatibility concerns, no internet required, and full read/write speed over your LAN. Mobile operating systems (iOS and Android) also support SMB through apps like Files and VLC, so the same share can serve your phone too.

This guide covers the specific setup and daily workflow for bi-directional file sharing between a Mac and a Windows machine running WSL2 Ubuntu, which is just about as complicated as it can get, but the concepts apply to any combination of SMB-capable platforms.

Architecture

There are two sharing directions to set up. The first makes WSL2 files visible on the Mac; the second makes Mac files visible inside WSL2.

Mac → WSL2 direction

Mac (macOS)
  |
  |  smb://WINDOWS_LAN_IP:4445/wsl-home
  v
Windows Host (port 4445)
  |  netsh portproxy --> WSL2 IP:445
  v
WSL2 Ubuntu (smbd on port 445, shares /home/your-linux-username)

WSL2 → Mac direction

WSL2 Ubuntu
  |
  |  /mnt/mac-share  (CIFS mount)
  v
Mac (port 445, shares /Users/YourMacUsername)

Port 4445 is used for the Mac → WSL2 direction to avoid clashing with Windows' own SMB service on port 445. A netsh portproxy rule on Windows forwards traffic from port 4445 on the Windows LAN IP to port 445 on the WSL2 IP. For the WSL2 → Mac direction no proxy is needed: the Mac is directly reachable on its own LAN IP at port 445.

Setup

Finding your IPs

You will need three IP addresses during setup. Run these commands once and note the results — WSL2's IP changes on every restart, but once step 7 is complete the portproxy script will handle that automatically.

WSL2 terminal

ip addr show eth0 | awk '/inet / {print $2}' | cut -d/ -f1

Mac terminal

ipconfig getifaddr en0

PowerShell

ipconfig | findstr /i "IPv4"

Use the Wi-Fi or Ethernet line — not vEthernet WSL.

Samba on WSL2

This makes your WSL2 home directory accessible from the Mac. All commands run inside WSL2 unless stated otherwise.

0. Enable systemd in WSL2

The Samba service is managed by systemd. Many WSL2 installations ship with systemd disabled, which would cause systemctl enable smbd (step 4) to silently fail. Check first:

WSL2 terminal

cat /etc/wsl.conf

If you see [boot] with systemd=true underneath, you're good — skip to step 1. If not, add it:

WSL2 terminal

sudo tee -a /etc/wsl.conf <<'EOF'
[boot]
systemd=true
EOF

Then restart WSL2 from a Windows PowerShell window (this closes all WSL2 sessions):

PowerShell

wsl --shutdown

Reopen your WSL2 terminal and confirm systemd is running before continuing:

WSL2 terminal

systemctl is-system-running

The output should be running (or degraded, which is also fine). If it says offline, the /etc/wsl.conf change did not take effect — double-check the file and try wsl --shutdown again.

1. Install Samba and CIFS utilities

WSL2 terminal

sudo apt update && sudo apt install -y samba cifs-utils

2. Define the share in `/etc/samba/smb.conf`

Open the file in a text editor:

WSL2 terminal

sudo nano /etc/samba/smb.conf

Scroll to the very end and append the following block, replacing your-linux-username with your actual WSL2 username. Save with Ctrl+O, confirm, then exit with Ctrl+X:

[wsl-home]
   path = /home/your-linux-username
   browseable = yes
   read only = no
   valid users = your-linux-username

3. Set a Samba password for your user

WSL2 terminal

sudo smbpasswd -a your-linux-username

This is separate from your Linux login password. You will use it when the Mac asks for credentials.

4. Enable and start smbd

WSL2 terminal

sudo systemctl enable smbd
sudo systemctl start smbd

5. Store Mac credentials for the reverse mount

Create /etc/samba/mac-credentials with your Mac account details. Replace YourMacUsername with your macOS account name and YourMacPassword with your macOS login password (the same password you use to unlock the Mac — not a separately configured SMB password):

WSL2 terminal

sudo tee /etc/samba/mac-credentials <<'EOF'
username=YourMacUsername
password=YourMacPassword
EOF

Lock down the file so only root can read it:

WSL2 terminal

sudo chmod 600 /etc/samba/mac-credentials

6. Add the Mac share to `/etc/fstab`

First create the mount point:

WSL2 terminal

sudo mkdir -p /mnt/mac-share

Next, find your Linux user ID and group ID — you will need them for the fstab entry:

WSL2 terminal

id your-linux-username

The output looks like uid=1000(your-linux-username) gid=1000(your-linux-username) .... Note the numeric values. Now open /etc/fstab:

WSL2 terminal

sudo nano /etc/fstab

Append the following line at the end, substituting MAC_LAN_IP, YourMacUsername, and the uid/gid values you just noted. Save and exit (Ctrl+O, Enter, Ctrl+X):

//MAC_LAN_IP/YourMacUsername /mnt/mac-share cifs credentials=/etc/samba/mac-credentials,uid=1000,gid=1000,x-systemd.automount,noauto 0 0

The x-systemd.automount,noauto flags mean the share is not mounted at boot (which would hang if the Mac is off) but is mounted transparently on the first access. Reload systemd so it picks up the new mount unit:

WSL2 terminal

sudo systemctl daemon-reload

Windows port proxy

How does this work?

WSL2 runs inside a lightweight VM with its own internal IP address. From the Mac's perspective, it cannot reach that IP directly — only the Windows machine's LAN IP is visible on your network. We therefore set up a port proxy rule on Windows: the Mac connects to port 4445 on the Windows LAN IP, and Windows silently forwards those packets to port 445 on the WSL2 VM. Port 4445 (not 445) is used because Windows already occupies port 445 for its own SMB service.

The WSL2 VM gets a fresh IP on every restart, so a hard-coded proxy rule would break after reboots. The fix is a short PowerShell script that looks up the current WSL2 IP and rewrites the proxy rule each time it runs. We save that script to disk and register it with Windows Task Scheduler so it fires automatically at every logon and startup.

All steps below run in Windows PowerShell opened as Administrator — search for "PowerShell" in the Start menu, right-click → Run as administrator.

1. Create the Scripts folder

We will store the portproxy script at C:\Scripts\update-wsl2-portproxy.ps1. Create the folder if it does not already exist:

PowerShell (Admin)

New-Item -ItemType Directory -Force -Path C:\Scripts

2. Create the portproxy script

The following command writes the script file directly from PowerShell. It reads the current WSL2 IP, removes any stale proxy rule on port 4445, then adds a fresh one pointing at the new IP:

PowerShell (Admin)

@'
$wsl2ip = (wsl hostname -I).Trim()
netsh interface portproxy delete v4tov4 listenport=4445 listenaddress=0.0.0.0 2>$null
netsh interface portproxy add    v4tov4 listenport=4445 listenaddress=0.0.0.0 connectport=445 connectaddress=$wsl2ip
'@ | Set-Content C:\Scripts\update-wsl2-portproxy.ps1

To confirm the file looks right, open it in Notepad:

PowerShell (Admin)

notepad C:\Scripts\update-wsl2-portproxy.ps1

3. Open port 4445 in the Windows Firewall

Without this, Windows will silently drop inbound packets from the Mac before they ever reach the proxy rule:

PowerShell (Admin)

New-NetFirewallRule -DisplayName "WSL2 SMB" -Direction Inbound -Protocol TCP -LocalPort 4445 -Action Allow

4. Run the script once now

This creates the proxy rule immediately without needing a reboot. PowerShell's default execution policy may block unsigned scripts — the -ExecutionPolicy Bypass flag overrides it for this single run:

PowerShell (Admin)

powershell.exe -ExecutionPolicy Bypass -File C:\Scripts\update-wsl2-portproxy.ps1

Verify that the rule was created:

PowerShell (Admin)

netsh interface portproxy show all

You should see a row with listen port 4445 and a connect address matching the WSL2 IP you noted earlier.

5. Register with Task Scheduler

This ensures the proxy rule is refreshed automatically on every Windows logon and startup, even after WSL2's IP changes:

PowerShell (Admin)

$action  = New-ScheduledTaskAction `
               -Execute   "powershell.exe" `
               -Argument  "-NonInteractive -ExecutionPolicy Bypass -File C:\Scripts\update-wsl2-portproxy.ps1"
$trigger = @(
    $(New-ScheduledTaskTrigger -AtLogOn),
    $(New-ScheduledTaskTrigger -AtStartup)
)
Register-ScheduledTask `
    -TaskName  "\WSL2\WSL2-Samba-PortProxy-Update" `
    -Action    $action `
    -Trigger   $trigger `
    -RunLevel  Highest `
    -Force

To confirm, open Task Scheduler (search Start menu), navigate to Task Scheduler Library → WSL2, and verify WSL2-Samba-PortProxy-Update is listed there.

File Sharing on Mac

This makes your Mac home directory (or any folder you choose) accessible from WSL2.

Open System Settings → General → Sharing and toggle File Sharing on.
Under Shared Folders, click + and add your home folder (/Users/YourMacUsername) or whichever directory you want WSL2 to reach.
Under Users, confirm your Mac account has Read & Write access. New shares default to Everyone: Read Only — if that's the case, click your user entry, click the dropdown next to it, and change it to Read & Write.
The share name defaults to your Mac username — this is the name used in the /etc/fstab line above (//MAC_LAN_IP/YourMacUsername).

File Sharing persists across reboots once enabled; no further configuration is needed on the Mac side.

Daily Workflow

Mac → WSL2 (access WSL2 files from Mac)

In Finder press Cmd+K and enter smb://WINDOWS_LAN_IP:4445/wsl-home.
Log in with username your-linux-username and your Samba password.
The WSL2 home directory mounts in Finder — drag, drop, edit in place, or copy freely.

To skip step 1 permanently, right-click the mounted share in the Finder sidebar and choose Add to Login Items.

WSL2 → Mac (access Mac files from WSL2)

Just use the path — no manual mount is needed because the share is configured to auto-mount on first access via /etc/fstab:

ls /mnt/mac-share/
cp ~/file /mnt/mac-share/Desktop/
cat /mnt/mac-share/.zshrc
rsync -av ~/project/ /mnt/mac-share/project/

After restarts

Event	Action needed
Windows / WSL2 restart	None — Task Scheduler updates the portproxy rule, systemd starts smbd
Mac restart	None — File Sharing re-enables automatically
Finder mount dropped	`Cmd+K` and reconnect

Common Commands

# Copy file from Mac to WSL2
cp /mnt/mac-share/somefile ~/

# Copy file from WSL2 to Mac Desktop
cp ~/somefile /mnt/mac-share/Desktop/

# Sync folder Mac -> WSL2
rsync -av /mnt/mac-share/project/ ~/project/

# Sync folder WSL2 -> Mac
rsync -av ~/project/ /mnt/mac-share/project/

# Check Samba is running
sudo systemctl status smbd

# Manually remount Mac share (if automount failed)
sudo mount /mnt/mac-share

# Check WSL2 is listening on port 445
ss -tlnp | grep 445

Key Files

File	Purpose
`/etc/samba/smb.conf`	Samba config — defines the `wsl-home` share
`/etc/samba/mac-credentials`	Mac login credentials for the CIFS mount (chmod 600)
`/etc/fstab`	Persistent Mac share mount with `x-systemd.automount`
`C:\Scripts\update-wsl2-portproxy.ps1`	Windows script that refreshes the portproxy rule on each restart
Windows Task Scheduler `\WSL2\WSL2-Samba-PortProxy-Update`	Runs the portproxy script at logon and startup

Troubleshooting

Symptom	Fix
Mac Finder "Connection Failed"	Check smbd is running in WSL2: `sudo systemctl status smbd`. Then in Windows run `netsh interface portproxy show all` to confirm the 4445 rule exists
Mac auth error	Run `sudo smbpasswd -e your-linux-username` in WSL2 to re-enable the Samba account
`/mnt/mac-share` empty or permission denied	Verify File Sharing is enabled on the Mac; run `ping MAC_LAN_IP` from WSL2 to confirm connectivity
Mount hangs on boot	The Mac was off — automount retries on first access, no action needed
After WSL2 restart, Mac can't connect	The Task Scheduler script may not have fired yet; wait 10 s or run the script manually from an Administrator PowerShell: `powershell.exe -ExecutionPolicy Bypass -File C:\Scripts\update-wsl2-portproxy.ps1`

Architecture

Setup

Finding your IPs

Samba on WSL2

0. Enable systemd in WSL2

1. Install Samba and CIFS utilities

2. Define the share in /etc/samba/smb.conf

3. Set a Samba password for your user

4. Enable and start smbd

5. Store Mac credentials for the reverse mount

6. Add the Mac share to /etc/fstab

Windows port proxy

1. Create the Scripts folder

2. Create the portproxy script

3. Open port 4445 in the Windows Firewall

4. Run the script once now

5. Register with Task Scheduler

File Sharing on Mac

Daily Workflow

Mac → WSL2 (access WSL2 files from Mac)

WSL2 → Mac (access Mac files from WSL2)

After restarts

Common Commands

Key Files

Troubleshooting

Comments

2. Define the share in `/etc/samba/smb.conf`

6. Add the Mac share to `/etc/fstab`