A Singularity plugin is a package that can be dynamically loaded by the Singularity runtime, augmenting Singularity with experimental, non-standard and/or vendor-specific functionality. Currently, plugins are able to add commands and flags to Singularity. In the future, plugins will also be able to interface with more complex subsystems of the Singularity runtime.
list command prints the currently installed plugins.
$ singularity plugin list There are no plugins installed.
Plugins are packaged and distributed as binaries encoded with the versatile
Singularity Image Format (SIF). However, plugin authors may also distribute the
source code of their plugins. A plugin can be compiled from its source code
compile command. A sample plugin
test-plugin is included with
the Singularity source code.
$ singularity plugin compile examples/plugins/test-plugin/
Upon successful compilation, a SIF file will appear in the directory of the plugin’s source code.
$ ls examples/plugins/test-plugin/ | grep sif test-plugin.sif
Currently, all plugins must be compiled from the Singularity source code tree.
Also, the plugins mechanism for the Go language that Singularity is written
in is quite restrictive - it requires extremely close version matching of
packages used in a plugin to the ones used in the program the plugin is
built for. Additionally Singularity is using build time config to get the
source tree location for
singularity plugin compile so that you don’t
need to export environment variables etc, and there isn’t mismatch between
package path information that Go uses. This means that at present you must:
Build plugins using the exact same version of the source code, in the same location, as was used to build the Singularity executable.
Use the exact same version of Go that was used to build the executable when compiling a plugin for it.
Every plugin encapsulates various information such as the plugin’s author, the
plugin’s version, etc. To view this information about a plugin, use the
$ singularity plugin inspect examples/plugins/test-plugin/test-plugin.sif Name: sylabs.io/test-plugin Description: This is a short test plugin for Singularity Author: Michael Bauer Version: 0.0.1
To install a plugin, use the
install command. This operation requires root
$ sudo singularity plugin install examples/plugins/test-plugin/test-plugin.sif $ singularity plugin list ENABLED NAME yes sylabs.io/test-plugin
After successful installation, the plugin will automatically be enabled. Any
plugin can be disabled with the
disable command and re-enabled with the
enable command. Both of these operations require root privilege.
$ sudo singularity plugin disable sylabs.io/test-plugin $ singularity plugin list ENABLED NAME no sylabs.io/test-plugin $ sudo singularity plugin enable sylabs.io/test-plugin $ singularity plugin list ENABLED NAME yes sylabs.io/test-plugin
Finally, to uninstall a plugin, use the
uninstall command. This operation
requires root privilege.
$ sudo singularity plugin uninstall sylabs.io/test-plugin Uninstalled plugin "sylabs.io/test-plugin". $ singularity plugin list There are no plugins installed.
Writing a Plugin¶
Developers interested in writing Singularity plugins can get started by reading the Go documentation for the plugin package. Furthermore, reading through the source code for the example test plugin will prove valuable. More detailed plugin development documentation is in the works and will be released at a future date.