System Manager GNU Shepherd 1.0.0 (formerly dmd) has been introduced, combining the capabilities of an init system and tools for managing system services. It is noted that assigning the number 1.0 after 21 years of development signifies the project's readiness and its compliance with the functionality requirements of modern init systems and service managers.
The project is being developed by the GNU Guix System distribution team as an alternative to the SysV-init init system, which supports dependencies. The managing daemon and utilities of Shepherd are written in Guile (one of the implementations of the Scheme language), which is also used to define settings and parameters for launching services. Shepherd is already employed in the GNU Guix System distribution and is also aimed at use in GNU/Hurd but can run on any POSIX-compliant OS for which Guile is available.
Shepherd udfører opgaver relateret til opstart og stop af tjenester, idet den tager hensyn til sammenhængen mellem dem, og dynamisk bestemmer og starter de tjenester, som den valgte tjeneste er afhængig af. Shepherd understøtter også identifikation af konflikter mellem tjenester og forhindrer deres samtidige udførelse. Projektet kan bruges som det primære init-system (init med PID 1), eller i en isoleret form til at styre baggrundsprocesser for enkeltbrugere (f.eks. til at starte tor, privoxy, mcron osv.) med de pågældende brugeres rettigheder.
Key innovations in GNU Shepherd 1.0.0:
- Support has been added for services that periodically execute commands or Scheme code according to a specified schedule.
- The command "herd status SERVICE" now displays high-level information about services, such as PID, command, and addresses where network requests are received, as well as summaries of recently added log messages. Additionally, this command now shows applicable user actions for the service and informs about the presence of a replacement service that will be applied after the current service is restarted.
- The command "herd status root" is no longer a synonym for "herd status" and displays information about the root Shepherd process.
- For Linux platforms, the ability to restart using the kexec mechanism ("reboot --kexec") has been provided to replace the Linux kernel without a physical reboot.
- A log-rotation service has been added, responsible for periodic rotation of logs and the removal of outdated logs.
- A system-log service has been added, which can be used as a replacement for the traditional syslogd system.
- A timer service has been added to execute commands at specified times, similar to the "at" utility. For example, "herd schedule timer at 07:00 -- mpg123 alarm.mp3".
- A transient service has been added for running commands in the background, similar to the systemd-run utility. For example, "herd spawn transient -d $PWD -- make -j4".
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