114 lines
3.3 KiB
Groff
114 lines
3.3 KiB
Groff
.TH backtunnel 1 "September 2025" "1.2" "BackTunnel – Reverse SSH Sharing Toolkit"
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.SH NAME
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backtunnel-share, backtunnel-access \- Secure reverse SSH folder sharing and access
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.SH SYNOPSIS
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.B backtunnel-share
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/path/to/folder with remoteuser:remotehost for <duration> [options]
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.B backtunnel-access
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/path/to/folder from remoteuser:remotehost [options]
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.SH DESCRIPTION
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\fBbacktunnel-share\fR starts a reverse SSH tunnel from the local (sharing) machine to a remote, reachable host.
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The tunnel exposes the local sshd (typically port 22) on a loopback port on the remote host using \fBssh -R\fR.
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The sharing ends automatically after the given \fIduration\fR via \fBtimeout\fR.
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With the \fB--invite\fR option, \fBbacktunnel-share\fR prints a ready-to-copy access command for the remote user,
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which can be pasted directly into a chat or terminal. The invite can also be rendered as a QR code or written to a file.
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\fBbacktunnel-access\fR mounts the shared folder from the remote side using \fBsshfs\fR by connecting to \fBlocalhost:<port>\fR on the remote host (the port exposed by \fBbacktunnel-share\fR).
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.SH OPTIONS
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.SS backtunnel-share options
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.TP
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.B -p, --tunnel-port <PORT>
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Remote port to bind with \fB-R\fR (default: 2222).
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.TP
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.B -l, --local-ssh-port <PORT>
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Local sshd port to forward to (default: 22).
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.TP
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.B -i, --invite
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Print a ready-to-copy invite command for the remote user.
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.TP
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.B --invite-mount <PATH>
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Mount point suggested in the invite (default: /mnt/remote-rssh).
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.TP
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.B --invite-file <FILE>
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Also write the invite text (including unmount hint) to the given file.
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.TP
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.B --qr
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Render the invite as a terminal QR code (requires \fBqrencode\fR).
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.SS backtunnel-access options
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.TP
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.B -p, --port <PORT>
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Remote port on which the reverse tunnel listens (default: 2222).
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.TP
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.B -m, --mount-point <PATH>
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Local mount point for sshfs (default: /mnt/remote-rssh).
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.SH ARGUMENTS
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.TP
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.B /path/to/folder
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Path to share (server) or to mount (client).
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.TP
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.B remoteuser:remotehost
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Or \fBremoteuser@remotehost\fR. The remote host that accepts the initial SSH connection.
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.TP
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.B <duration>
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Time to keep the share active. Accepts \fBn\fR\fIs\fR|\fIm\fR|\fIh\fR|\fId\fR forms, e.g. 30m, 2h, 1d. Passed to \fBtimeout\fR.
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.SH EXAMPLES
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.TP
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Share for 2 hours on default ports:
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.B backtunnel-share
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/home/user/docs with alice@vps.example.com for 2h
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.TP
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Share for 1 day, using custom ports:
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.B backtunnel-share
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/home/user/docs with alice:vps.example.com for 1d -p 4422 -l 2222
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.TP
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Share with invite printed:
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.B backtunnel-share
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/home/user/docs with alice@vps.example.com for 2h -i
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.TP
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Share with QR invite:
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.B backtunnel-share
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/home/user/docs with alice@vps.example.com for 2h -i --qr
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.TP
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Mount with default port and mount point:
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.B backtunnel-access
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/home/user/docs from alice@vps.example.com
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.TP
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Mount with custom port and mount point:
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.B backtunnel-access
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/home/user/docs from alice@vps.example.com -p 4422 -m /mnt/alice-docs
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.SH NOTES
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By default, \fBssh -R\fR binds to 127.0.0.1 on the remote side, limiting access to local users on the remote machine.
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The client connects to \fBlocalhost:<port>\fR from the remote host.
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The invite feature is intended for convenience: copy-paste the printed command into chat for the remote user.
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Unmount with \fBfusermount -u <mountpoint>\fR after use.
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.SH SEE ALSO
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ssh(1), sshfs(1), timeout(1), autossh(1), qrencode(1), fusermount(1)
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.SH AUTHOR
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Matjaž Mozetič
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