Systemd improves image features and adds varlink API

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2024-12-24 23:30:05

The systemd v257 release brings a number of incremental enhancements to various components and utilities for working with Linux systems. This includes more support for varlink, automated downloading of disk images at boot time, and a number of improvements to the secure-boot process for unified kernel images (UKIs), which we have covered in a separate article.

Lennart Poettering announced the release The release was announced on December 10 to the systemd-devel mailing list, and Lennart Poettering followed up with a blog post that linked to his Mastodon threads about new features in v257.

One of the interesting changes in systemd v257 is the project leaning into varlink. Poettering has been championing the varlink inter-process communication (IPC) protocol as an alternative to D-Bus for some time. (LWN covered varlink in 2018, shortly after its announcement.) At the All Systems Go! (ASG) conference in September, he delivered a "Varlink Now!" presentation to explain why systemd is adopting it heavily, and to make the case for other software to adopt it as well. (A video of the talk is available, as are the slides.)

One of the primary problems with D-Bus, at least from the systemd perspective, is that it is not available until late in the boot process—too late for many things systemd needs to do. Poettering also said that it is easier to write varlink services than D-Bus services, because a varlink service can handle each connection in a separate process: