saned

saned [-a] [-d] [-o outfile] [-u username]

-a
    Auto-enable. Used when saned is run by a super-server (like inetd or xinetd) to automatically enable debugging and logging.

-d
    Debug mode. Increases the verbosity of log messages, showing more details about internal operations. Can be specified multiple times (e.g., -dd) for even more verbose output.

-o outfile
    Output file. Redirects debugging and other log messages to the specified outfile instead of standard error.

-u username
    Run as user. Changes the user ID of the saned process to username after binding to the SANE port. This is a security measure, typically used when saned is started as root.

The saned command provides a network daemon that allows remote clients to access scanners connected to the local machine. It is part of the SANE (Scanner Access Now Easy) project, which offers a standardized API for accessing various scanning devices. When saned is running, SANE-enabled client applications (such as scanimage or xsane) on remote machines can connect to the host running saned and utilize its locally connected scanners as if they were directly attached. This is particularly useful for sharing a single scanner among multiple users or computers on a network.

saned typically listens on a well-known port (TCP 6566) for incoming connections, receives scanning requests from clients, passes them to the appropriate local SANE backend (driver) for the scanner, and returns the scan data back to the client. It can be run as a standalone daemon or managed by super-servers like inetd or xinetd.

Configuring saned requires careful attention to network security. By default, it may allow access from any host if not properly configured in saned.conf. It's crucial to restrict access to trusted clients or networks to prevent unauthorized use of the scanner or potential security vulnerabilities. Firewall rules must also be configured to allow incoming connections on the SANE port (TCP 6566) for clients to reach saned. Running saned as root and failing to drop privileges via the -u option can also pose a security risk.

The primary configuration file for saned is /etc/sane.d/saned.conf. This file controls which client IP addresses or hostnames are allowed to connect to the saned server. It also specifies other options, such as the user under which saned should run if not specified on the command line. Proper configuration of this file is essential for both functionality and security.

The SANE backend configuration files, located in /etc/sane.d/ (e.g., epson.conf, net.conf), also play a role as saned relies on these to find and communicate with local scanners.

saned can be deployed in two main ways:
1. Super-server management: This is the most common method. inetd or xinetd listens for incoming connections on the SANE port and then launches a saned instance for each connection. This conserves resources as saned only runs when needed. Configuration usually involves adding an entry to /etc/services and /etc/inetd.conf or /etc/xinetd.d/saned.
2. Standalone daemon: saned can be run directly as a persistent daemon. This might be preferred in high-traffic environments where the overhead of launching saned for each connection is undesirable. When run standalone, it typically needs to be started at boot time and manages multiple concurrent connections itself.

When troubleshooting issues with saned, enabling debug mode (-d or -dd) is crucial. If saned is managed by a super-server, you might need to use the -a option to enable auto-debugging, which logs output to a file (specified with -o). Examining the debug output can help identify problems related to network connectivity, permissions, scanner detection, or backend communication. Ensure that logging is redirected to a writable file if running as a non-privileged user.

The SANE (Scanner Access Now Easy) project, which includes saned, began in the mid-1990s with the goal of providing a standardized API for scanner hardware. saned was developed to extend this functionality over networks, allowing remote access to scanners. Its core function has remained consistent since its inception, evolving primarily in terms of robustness, security features, and support for new SANE backends.

sane-backends(7), saned.conf(5), scanimage(1), xsane(1), inetd(8), xinetd(8)