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What's New in {Singularity} 4.0

This section highlights important changes in {Singularity} 4.0 that are of note to system administrators. See also the "What's New" section in the User Guide for user-facing changes.

OCI-Compatibility

  • {Singularity}'s OCI-mode, which was experimental in 3.11, is now expanded and fully supported. It is enabled via --oci on the command line, or by setting oci mode = true in singularity.conf.
  • OCI-mode runs containers unprivileged, using a low-level OCI runtime rather than {Singularity}'s own native runtime. {Singularity}'s setuid starter executable is not used on OCI-mode, even when setuid is enabled for the native runtime.
  • OCI-mode uses OCI-SIF images, a variant of the Singularity Image Format. These images cannot be run using earlier versions of {Singularity}.
  • OCI-mode supports the Container Device Interface (CDI) standard for enabling access to GPUs and other devices within containers.

Requirements

  • {Singularity} uses squashfuse_ll or squashfuse, which is now built from a git submodule unless --without-squashfuse is specified as an argument to mconfig. When built with --without-squashfuse, squashfuse_ll or squashfuse should be located on PATH. Version 0.2.0 or later is required.
  • OCI-mode requires sqfstar or tar2sqfs to be :ref:`installed on the system <sqfstar>` in order to create OCI-SIF images.
  • OCI-mode requires fuse-overlayfs to be installed on the system (from a distribution package), to fully support unprivileged overlays.
  • OCI-mode requires that either runc or crun is installed on the system (from a distribution package).
  • OCI-mode requires that subuid/subgid mappings have been configured for users, in the same manner as documented for the :ref:`fakeroot <fakeroot>` feature.

Packaging

  • RPM packages now use /var/lib/singularity (rather than /var/singularity) to store local state files.
  • Bash completions are now installed to the modern share/bash-completion/completions location, rather than under etc.

CLI

Caching

  • Caching of OCI blobs is now architecture aware. If older versions of {Singularity} are not being used in parallel, users should run singularity cache clean to recover space used by obsolete cached blobs.

Plugins

  • Support for image driver plugins, deprecated at 3.11, has been removed. Unprivileged kernel overlay is supported without a plugin. In singularity.conf, the image driver directive has been removed, and enable overlay no longer supports the driver option.