Singularity-Util

A Docker based container that acts as a multi-purpose wrapper for Singularity. It is ideal for integrating into Docker centric build systems or for use platforms (OSX/Windows) where Singularity cannot be directly installed.

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Usage

The singularity-util container will accept the majority of Singularity commands with the caveat that all paths MUST be relative to the /target directory within the container. /target acts as the current working directory for all the Singularity based commands.

docker pull arcts/singularity-util
docker run --rm --privileged -v $(pwd):/target:rw arcts/singularity-util <command> <args>

Supported Singularity commands include bootstrap, copy, create, expand, exec, export, import, run, shell, and test. For the Singularity specific usage commands, please see their command reference documentation.

Non-Singularity commands include build and debug.

• build accepts rpm, deb or nothing for both as parameters and will build packages via the provided packaging system, then drop them in the /target directory.
• debug Executes an arbitrary command within the singularity-util container and is useful for troubleshooting. To drop to a bash shell simply execute: debug bash.

Examples:

Building Packages

$ docker run --rm -v $(pwd):/target arcts/singularity-util build deb
   ...
$ ls *.rpm
  singularity-2.2-0.1.x86_64.rpm		singularity-devel-2.2-0.1.x86_64.rpm

Building a CentOS 6 Singularity Container

$ docker run --rm --privileged -v $(pwd):/target arcts/singularity-util create centos6.img
  Creating a new image with a maximum size of 768MiB...
  Executing image create helper
  Formatting image with ext3 file system
  Done
$ docker run --rm --privileged -v $(pwd):/target arcts/singularity-util import centos6.img docker://centos:6
  library/centos:6
  Downloading layer: sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4
  Downloading layer: sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4
  Downloading layer: sha256:32c4f4fef1c65e47e41704aabeb99e984f1c01e3541e48354b09300fa5b2d068
  Downloading layer: sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4
  Adding Docker CMD as Singularity runscript...
  Bootstrap initialization
  No bootstrap definition passed, updating container
  Executing Prebootstrap module
  Executing Postbootstrap module
  Done.
$ docker run -it --rm --privileged -v $(pwd):/target arcts/singularity-util exec centos6.img cat /etc/system-release
  CentOS release 6.8 (Final)

Expanding an Image

$ docker run --rm --privileged -v $(pwd):/target arcts/singularity-util expand --size 512 centos6.img
  Expanding existing image with a size of 512MiB...
  Executing image expand helper
  Checking image (/sbin/mkfs.ext3)
  e2fsck 1.42.13 (17-May-2015)
  Growing file system
  resize2fs 1.42.13 (17-May-2015)
  Done.

Building Alternate Versions

Alternate versions of Singularity can be baked into the singularity-util container by supplying the Docker build argument SINGULARITY_VERSION. This should correlate to a git tag, branch or commit id within the Singularity Github repo. This build argument will update the image label Singularity.Version.