dbclient

Connect to a remote host

$ dbclient [user]@[host]

$ dbclient [user]@[host] -p 2222

$ dbclient -i [path/to/key_file] [user]@[host]

$ dbclient [user]@[host] -t [command] [argument1 argument2 ...]

$ dbclient -A [user]@[host]

dbclient [options] user@host [command]

-h
    Display help message and exit.

-V
    Display version information and exit.

-p port
    Connect to the specified port on the remote host. Defaults to 22.

-i identity_file
    Specify the path to the private key file for authentication.

-l username
    Specify the username to log in as on the remote host.

-y
    Always accept new host keys without prompting. Use with extreme caution as it bypasses host key verification, making it vulnerable to man-in-the-middle attacks.

-N
    Do not execute a remote command or allocate a pseudo-terminal. Useful for port forwarding only.

-T
    Disable pseudo-terminal allocation. Useful for executing commands non-interactively.

-C
    Enable compression for the connection, which can be useful over slow links.

-L local_port:remote_host:remote_port
    Local port forwarding. Forward local port to a remote host and port via the SSH tunnel.

-R remote_port:local_host:local_port
    Remote port forwarding. Forward a remote port to a local host and port via the SSH tunnel.

-W host:port
    Proxy forwarding. Forward stdio to a remote host and port.

-s
    Request subsystem (e.g., used for sftp). If this option is used, command specifies the subsystem name.

-f
    Go to background after successful authentication. Requires -N (no command).

user@host
    The remote user and hostname or IP address to connect to.

[command]
    An optional command to execute on the remote host. If not provided, an interactive shell will be opened.

dbclient is the client program for Dropbear, a small and efficient SSH 2 server and client. It's designed to be lightweight and resource-friendly, making it suitable for embedded systems, routers, and environments where OpenSSH might be considered too large.

It allows users to securely connect to remote servers, execute commands, and transfer files over an encrypted channel. While offering a subset of OpenSSH's features, it provides essential SSH protocol version 2 functionality, focusing on minimal overhead and efficient operation for systems with constrained resources.

Feature Limitations: Compared to OpenSSH, dbclient has fewer features, notably lacking support for X11 forwarding, SSH agent forwarding (though private key files can be specified), and a wider range of authentication methods.

Security Warning (-y): Using the -y option is highly discouraged in production environments as it disables critical host key verification, making connections susceptible to active man-in-the-middle attacks. Always verify host keys manually or via known_hosts.

Community Support: While stable, Dropbear and its client generally have a smaller community and less extensive public documentation than OpenSSH.

dbclient is known for its exceptional portability and minimal resource requirements. Its small binary size and low memory footprint make it an ideal choice for resource-constrained environments like IoT devices, network appliances, and older hardware where a full-fledged OpenSSH installation might be too heavy.

Dropbear, including its client dbclient, was developed by Matt Johnston with its initial release around 2003. It emerged as a lightweight, small-footprint alternative to the more feature-rich OpenSSH suite, specifically targeting embedded Linux systems, routers, and devices with limited memory and storage. Its design prioritizes efficiency and low resource consumption, which has cemented its place in the embedded systems world.

dropbear(8), ssh(1), scp(1), sftp(1)