New in Singularity version 2.4 you can use the instance command group to run instances of containers in the background. This is useful for running services like databases and web servers. The instance.start command lets you initiate a named instance in the background.


To initiate a named instance of a container, you must call the instance.start command with 2 arguments: the name of the container that you want to start and a unique name for an instance of that container. Once the new instance is running, you can join the container’s namespace using a URI style syntax like so:

$ singularity shell instance://<instance_name>

You can specify options such as bind mounts, overlays, or custom namespaces when you initiate a new instance of a container with instance.start. These options will persist as long as the container runs.

For a complete list of options see the output of:

singularity help instance.start


These examples use a container from Singularity Hub, but you can use local containers or containers from Docker Hub as well. For a more detailed look at instance usage see Running Instances.

Start an instance called cow1 from a container on Singularity Hub

$ singularity instance.start shub://GodloveD/lolcow cow1

Start an interactive shell within the instance that you just started

$ singularity shell instance://cow1
Singularity GodloveD-lolcow-master.img:~> ps -ef 
ubuntu       1     0  0 20:03 ?        00:00:00 singularity-instance: ubuntu [cow1]
ubuntu       3     0  0 20:04 pts/0    00:00:00 /bin/bash --norc
ubuntu       4     3  0 20:04 pts/0    00:00:00 ps -ef
Singularity GodloveD-lolcow-master.img:~> exit

Execute the runscript within the instance

$ singularity run instance://cow1
/ Clothes make the man. Naked people have \
| little or no influence on society.      |
|                                         |
\ -- Mark Twain                           /
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

Run a command within a running instance.

$ singularity exec instance://cow1 cowsay "I like blending into the background"
< I like blending into the background >
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||