ADBD

ADBD, short for Android Debug Bridge Daemon, is the background service on Android devices that implements the server side of the Android Debug Bridge (ADB). It allows a host computer running the ADB client to issue commands to the device, including shell access, file transfers, and package management.

Operation and scope

adbd runs on the device and communicates with the ADB client on the host over USB or over a network connection (TCP/IP). It authenticates connections using RSA key pairs and, once authenticated, relays commands and streams between the host and the device. Typical tasks include executing shell commands, pushing and pulling files, installing or uninstalling apps, and collecting logs.

Lifecycle and access

On startup, the device’s init system launches adbd as part of the system services. Its access is controlled by device security settings; in particular, USB debugging and host authorization must be enabled so that the host computer’s key can be trusted. When a new host connects, the device may prompt the user to authorize the host’s public key. Adbd operates with the device’s permissions, and its capabilities can be restricted by the device’s security policies or by using root access when the device is rooted.

Security considerations

ADBD relies on cryptographic authentication to prevent unauthorized control of the device. Leaving USB debugging enabled or exposing adbd over a network without proper protection can create security risks. Users should enable USB debugging only when needed and authorize hosts carefully; disable or revoke authorization when not in use.

Troubleshooting

Common issues include a device being “unauthorized” by the host, adbd not running, or connectivity problems over USB or TCP/IP. Solutions typically involve authorizing the host on the device, restarting the ADB server on the host, or restarting adbd on the device.