BackTunnel

BackTunnel lets you share and mount folders between Linux machines behind NAT or firewalls using just two friendly commands. No central servers. No cloud uploads. Temporary, peer-to-peer, SSH-based.

⚡ Quick Start (3 steps)

On the sharing machine (server):
```
backtunnel-share ~/Documents with user@remotehost for 2h -i
```
→ Opens a tunnel for 2 hours and prints an invite.

Send the invite (via chat, email, QR). It looks like:

backtunnel-auth-setup -p 2222 user@localhost
backtunnel-access '/home/alice/Documents' from user@remotehost -p 2222 -m "$HOME/remote-rssh"

On the accessing machine (client):

mkdir -p ~/remote-rssh
backtunnel-auth-setup -p 2222 user@localhost
backtunnel-access '/home/alice/Documents' from user@remotehost -p 2222 -m ~/remote-rssh

→ Folder is mounted at ~/remote-rssh.

Unmount afterwards with:

fusermount -u ~/remote-rssh

🚀 Why BackTunnel?

Works behind NAT/firewalls: reverse SSH tunnels, no port forwarding needed.
Private by design: no third-party relays or cloud.
Temporary by default: shares auto-stop after chosen duration.
Simple invites: send one-liners (or QR codes) to colleagues.
Safe: restricted SFTP-only keys ensure no shell access.
Desktop integration: right-click folders in Dolphin to share or access.

✨ Commands

`backtunnel-share` — start a share

(sharing side)

backtunnel-share /path/to/folder with user@remotehost for <duration> [options]

Duration formats: 30m, 2h, 1d Key options:

-p, --tunnel-port <PORT> — Remote port (default: 2222)
-l, --local-ssh-port <PORT> — Local SSHD port (default: 22)
-i, --invite — Print a ready-to-copy invite
--invite-mount <PATH> — Suggested mount point (default: ~/remote-rssh)
--qr — Show invite as QR code

`backtunnel-access` — mount a share

(accessing side)

backtunnel-access /path/to/folder from user@remotehost [options]

Options:

-p, --port <PORT> — Remote tunnel port (default: 2222)
-m, --mount-point <PATH> — Local mount point (default: ~/remote-rssh)

Unmount with:

fusermount -u ~/remote-rssh

📁 Profiles

Simplify frequent shares with ~/.config/backtunnel/profiles.ini. Example:

[default]
tunnel_port=4422
invite_mount=$HOME/shared

[work]
user=alice
host=vps.example.com
tunnel_port=4423

Use with:

backtunnel-share ~/reports with @work for 6h -i

🔒 Security

Restricted keys: usable only through the tunnel (127.0.0.1).
SFTP-only: enforced with internal-sftp,restrict.
Temporary: ends when the tunnel closes.

🖥️ Dolphin Integration

After install, Dolphin menus appear:

Share via BackTunnel… — GUI wizard for remote, duration, ports, invite.
Access via BackTunnel… — GUI wizard for remote, port, mount point.

Logs:

~/.local/state/backtunnel/servicemenu.*.log

📦 Install

sudo bash scripts/install.sh
make init   # copy example profiles.ini

Uninstall:

sudo bash scripts/uninstall.sh

Arch Linux:

makepkg -si

📖 Man Page

man backtunnel

🧾 License

📝 Cheat Sheet (TL;DR)

Start a share:

backtunnel-share ~/Documents with user@remotehost for 2h -i

Send this invite to your colleague:

backtunnel-auth-setup -p 2222 user@localhost
backtunnel-access '/home/user/Documents' from user@remotehost -p 2222 -m ~/remote-rssh

On the client:

mkdir -p ~/remote-rssh
backtunnel-auth-setup -p 2222 user@localhost
backtunnel-access '/home/user/Documents' from user@remotehost -p 2222 -m ~/remote-rssh

Unmount:

fusermount -u ~/remote-rssh

README.md Unescape Escape

BackTunnel – Secure Reverse SSH Folder Sharing Toolkit