cupsd is the server daemon for the CUPS (Common UNIX Printing System) print server. CUPS is a widely used printing system for Unix-like operating systems, including Linux and macOS. The cupsd daemon is responsible for managing print queues, processing print jobs, and providing printing services to client applications.
When the cupsd daemon is running, it listens for incoming print requests from client applications and handles the printing process. Here are some key functionalities of cupsd:
- Print Queue Management: cupsd manages print queues, which are logical representations of physical printers or virtual printers. It maintains the status of print queues, including information about the print jobs in the queue, their priority, and their progress.
- Job Processing: cupsd processes print jobs submitted by client applications. It handles tasks such as job scheduling, job prioritization, and job routing to the appropriate print queues.
- Printer Configuration: cupsd allows configuration of printers and print queues. Administrators can use cupsd to add or remove printers, set printer properties (such as paper size, resolution, or print quality), and define access control rules for printers.
- Printer Sharing: cupsd supports printer sharing, allowing multiple clients on a network to access and use shared printers. It provides mechanisms for printer discovery, authentication, and secure printing.
- Job Filtering: cupsd supports job filtering, which involves applying filters to print data to perform tasks such as format conversion, image manipulation, or adding watermarks. These filters can be configured to process print jobs based on specific criteria.
- Logging and Monitoring: cupsd logs various events and activities related to printing, including print job status updates, error messages, and administrative actions. It provides logging and monitoring capabilities to help administrators diagnose and troubleshoot printing issues.
The cupsd daemon is typically started automatically during system boot and runs as a background process. It listens on a specified network port (usually port 631) for incoming print requests. Administrators can interact with cupsd using command-line tools, web-based administration interfaces, or graphical tools to manage printers, print queues, and other printing-related configurations.
Please note that the specific configuration and behavior of cupsd may vary depending on the operating system and the version of CUPS you are using. It is recommended to refer to the documentation or manual pages for cupsd for detailed information on configuration options, command-line tools, and other aspects of managing the CUPS print server.
cupsd Command Examples
1. Start cupsd in the background, aka. as a daemon:
# cupsd
2. Start cupsd on the [f]oreground:
# cupsd -f
3. [l]aunch cupsd on-demand (commonly used by launchd or systemd):
# cupsd -l
4. Start cupsd using the specified [c]upsd.conf configuration file:
# cupsd -c /path/to/cupsd.conf
5. Start cupsd using the specified cups-file[s].conf configuration file:
# cupsd -s path/to/cups-files.conf
6. [t]est the [c]upsd.conf configuration file for errors:
# cupsd -t -c /path/to/cupsd.conf
7. [t]est the cups-file[s].conf configuration file for errors:
# cupsd -t -s /path/to/cups-files.conf
8. Display all available options:
# cupsd -h