3. Pulling and Running Containers from the Cloud¶

Lesson Objectives

Pull a container from the cloud
Run a container that is on the cloud

Questions

How do I get a container that lives online, such as on Docker Hub?
Do I always have to download a container before I can use it?

Sometimes you might not have a container file sitting in front of you that you want to use. Most of the time, your container might be sitting on the internet somewhere, like on Docker Hub. There are two ways you can interact with containers that are on the cloud:

Pull the image from the cloud first using pull, then run the container directly from the computer, or
Run the container directly using the run, exec, or shell command.

In this lesson, we will look at both of these methods.

Pulling containers using the `pull` command¶

You can pull a container from the cloud by performing the following command:

apptainer pull output_name.sif <URI>

where:

output_name.sif: Is the name you want to give to the container you pull/download
<URI>: This is the URL to download the container from.

Note

Pulling a container just means downloading a container from the internet.

For example, consider that we want to pull a container that contains Alpine, which is a very lightweight operating system. To do this, we can type into the terminal:

apptainer pull my_alpine.sif docker://alpine

If you do this in the terminal, you will see the following:

user.name@computer-name:~$ apptainer pull my_alpine.sif docker://alpine
INFO:    Converting OCI blobs to SIF format
INFO:    Starting build...
INFO:    Fetching OCI image...
3.7MiB / 3.7MiB [=============================================================================] 100 % 242.0 KiB/s 0s
INFO:    Extracting OCI image...
INFO:    Inserting Apptainer configuration...
INFO:    Creating SIF file...
[=========================================================================================================] 100 % 0s

What you can see is Apptainer is downloading and constructing the container on your computer. We can now see that we have made a file called my_alpine.sif:

user.name@computer-name:~$ ls
my_alpine.sif

We can now use exec or shell to run Unix commands on the container:

Performing the exec in the my_alpine.sif container, we see:

user.name@computer-name:~$ apptainer exec my_alpine.sif echo Hello World!
Hello World!

Performing the shell in the my_alpine.sif container, we see:

user.name@computer-name:~$ apptainer shell my_alpine.sif
Apptainer> echo Hello Mercury!
Hello Mercury!
Apptainer> echo Hello Venus!
Hello Venus!
Apptainer> echo Hello Earth!
Hello Earth!
Apptainer> echo Hello Mars!
Hello Mars!
Apptainer> echo Hello Jupiter!
Hello Jupiter!
Apptainer> echo Hello Saturn!
Hello Saturn!
Apptainer> echo Hello Neptune!
Hello Neptune!
Apptainer> exit
exit

Running a container directly from the cloud¶

You can also skip the pull step entirely if you do not want to directly download the container onto your computer. You can do this by using the run, exec or shell command, where you call the address of the container on the cloud rather than the sif file.

For example, consider that we want to perform Hello World! on the Alpine container directly, rather than pulling it first then running it. To do this, we would do the following in the terminal:

apptainer exec docker://alpine echo Hello World!

See that we have replaced my_alpine.sif from the previous section with docker://alpine. Doing this will give the following:

user.name@computer-name:~$ apptainer exec docker://alpine echo Hello World!
INFO:    Converting OCI blobs to SIF format
INFO:    Starting build...
INFO:    Fetching OCI image...
3.7MiB / 3.7MiB [================================================================================================================================================================================] 100 % 517.2 KiB/s 0s
INFO:    Extracting OCI image...
INFO:    Inserting Apptainer configuration...
INFO:    Creating SIF file...
[============================================================================================================================================================================================================] 100 % 0s
Hello World!

or if you have already downloaded Alpine once before, you may get the image straight from the cache:

user.name@computer-name:~$ apptainer exec docker://alpine echo Hello World!
INFO:    Using cached SIF image
Hello World!

Following this, if you want to shell in the docker://alpine container, we see:

user.name@computer-name:~$ apptainer shell docker://alpine
INFO:    Using cached SIF image
Apptainer> echo Hello Mercury!
Hello Mercury!
Apptainer> echo Hello Venus!
Hello Venus!
Apptainer> echo Hello Earth!
Hello Earth!
Apptainer> echo Hello Mars!
Hello Mars!
Apptainer> echo Hello Jupiter!
Hello Jupiter!
Apptainer> echo Hello Saturn!
Hello Saturn!
Apptainer> echo Hello Neptune!
Hello Neptune!
Apptainer> exit
exit

In this case, I am using the version of Alpine that is currently stored in the Apptainer cache.

Exercises¶

Question 1

How would you pull the image docker://python:3.14-alpine from Docker?

Solution

Type into the terminal

apptainer pull my_python3.14.sif docker://python:3.14-alpine

where I have chosen to call this container my_python3.14.sif:

user.name@computer-name:~$ apptainer pull my_python3.14.sif docker://python:3.14-alpine
INFO:    Converting OCI blobs to SIF format
INFO:    Starting build...
INFO:    Fetching OCI image...
12.8MiB / 12.8MiB [==================================================================================================================================================================================] 100 % 0.0 b/s 0s
3.7MiB / 3.7MiB [====================================================================================================================================================================================] 100 % 0.0 b/s 0s
450.0KiB / 450.0KiB [================================================================================================================================================================================] 100 % 0.0 b/s 0s
INFO:    Extracting OCI image...
INFO:    Inserting Apptainer configuration...
INFO:    Creating SIF file...
[============================================================================================================================================================================================================] 100 % 0s

Question 2

How can I directly run python from the cloud image docker://python:3.14-alpine using the run?

Solution

Type into the terminal

apptainer run docker://python:3.14-alpine

This runs Python directly from the cloud image, dropping you straight into the Python interpreter:

user.name@computer-name:~$ apptainer run docker://python:3.14-alpine
INFO:    Using cached SIF image
Python 3.14.4 (main, Apr  8 2026, 17:40:50) [GCC 15.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> print('Hello Earth!')
Hello Earth!
>>> exit()

In this case, because I have already downloaded the docker://python:3.14-alpine image once before, Apptainer is using the cached version of docker://python:3.14-alpine.

Keypoints

Can pull a container from the cloud using the pull command
Can run a container directly from the cloud using run, exec, or shell

3. Pulling and Running Containers from the Cloud¶

Pulling containers using the pull command¶

Running a container directly from the cloud¶

Exercises¶

Pulling containers using the `pull` command¶