v3.6.0-rc.4 - 2020-06-01

This is the fourth pre-release / release candidate for the upcoming Singularity 3.6.0

This is a new version of Singularity with many new features, bug fixes, and other improvements detailed below. Some behaviour has changed. Please read the release notes below carefully. Documentation is currently being updated for 3.6.0 and will reflect the changes prior to the stable release.

To ensure a stable 3.6.0 release we'd appreciate any and all testing you're able to perform.

Many thanks to those who have contributed code, bug reports, and testing!

As always, please report any bugs to: https://github.com/sylabs/singularity/issues/new

If you think that you've discovered a security vulnerability please report it to security@sylabs.io - see the security policy at https://sylabs.io/security-policy for information.

New features / functionalities

• Singularity now supports the execution of minimal Docker/OCI
  containers that do not contain /bin/sh, e.g. docker://hello-world.
  
• A new cache structure is used that is concurrency safe on a filesystem that
  supports atomic rename. If you downgrade to Singularity 3.5 or older after
  using 3.6 you will need to run singularity cache clean.
  
• A plugin system rework adds new hook points that will allow the
  development of plugins that modify behavior of the runtime. An image driver
  concept is introduced for plugins to support new ways of handling image and
  overlay mounts. Plugins built for <=3.5 are not compatible with 3.6.
  
• The --bind flag can now bind directories from a SIF or ext3 image into a
  container.
  
• The --fusemount feature to mount filesystems to a container via FUSE
  drivers is now a supported feature (previously an experimental hidden flag).
  This permits users to mount e.g. sshfs and cvmfs filesystems to the
  container at runtime.
  
• A new -c/--config flag allows an alternative singularity.conf to be
  specified by the root user, or all users in an unprivileged installation.
  
• A new --env flag allows container environment variables to be set via the
  Singularity command line.
  
• A new --env-file flag allows container environment variables to be set from
  a specified file.
  
• A new --days flag for cache clean allows removal of items older than a
  specified number of days. Replaces the --name flag which is not generally
  useful as the cache entries are stored by hash, not a friendly name.
  

Changed defaults / behaviours

• Environment variables prefixed with SINGULARITYENV_ always take
  precedence over variables without SINGULARITYENV_ prefix.
  
• The %post build section inherits environment variables from the base image.
  
• %files from ... will now follow symlinks for sources that are directly
  specified, or directly resolved from a glob pattern. It will not follow
  symlinks found through directory traversal. This mirrors Docker multi-stage
  COPY behaviour.
  
• Restored the CWD mount behaviour of v2, implying that CWD path is not recreated
  inside container and any symlinks in the CWD path are not resolved anymore to
  determine the destination path inside container.
  
• The %test build section is executed the same manner as singularity test image.
  
• --fusemount with the container: default directive will foreground the FUSE
  process. Use container-daemon: for previous behavior.
  

Deprecated / removed commands

• Removed --name flag for cache clean; replaced with --days.
  

Bug Fixes

• Don't try to mount $HOME when it is / (e.g. nobody user).
  
• Process %appinstall sections in order when building from a definition file.
  
• Ensure SINGULARITY_CONTAINER, SINGULARITY_ENVIRONMENT and the custom
  shell prompt are set inside a container.
  
• Honor insecure registry settings from /etc/containers/registries.conf.
  
• Fix http_proxy env var handling in yum bootstrap builds.
  
• Disable log colorization when output location is not a terminal.
  
• Check encryption keys are usable before beginning an encrypted build.
  
• Allow app names with non-alphanumeric characters.
  
• Use the base metapackage for arch bootstrap builds - arch no longer has a
  base group.
  
• Ensure library client messages are logged with --debug.
  
• Do not mount $HOME with --fakeroot --contain.
  
• Fall back to underlay automatically when using a sandbox on GPFS.
  
• Fix Ctrl-Z handling - propagation of signal.