Basic information about images

• Basic information about images
  • The main features of the images provided by CSC
  • Images
    • CentOS-7
    • CentOS-7-Cuda
    • CentOS-8-Stream and CentOS-9-Stream
    • AlmaLinux-8 and AlmaLinux-9
    • Ubuntu-22.04, 20.04 and 18.04 LTS
  • Snowflake images
    • cirros

CSC provides a set of standard images that are well suited for cloud use. In most cases, you can use these images instead of creating your own. The images are created automatically using diskimage-builder. If you are interested in the details of how these images are created, see this GitHub page. The images are updated at regular intervals so that they contain the latest security updates at the time virtual machines are launched.

It is possible that for some use cases the automatically created images are not suitable. In this case, it is possible to create your own images and use them instead. However, there are some caveats to consider when creating your own images that you would not need to consider when using the default images. For more information,, see Advanced images

The main features of the images provided by CSC

The images provided by CSC are mostly the same as upstream.

• Most of the images come with the pre-configured username cloud-user, though there are some exceptions to this rule.
• We make sure that the images are updated before releasing them, so that we are sure that they work.
• The -Cuda images come preinstalled with the latest CUDA drivers.
• We enable automatic updates.
• We disable password login.
• We sometimes add some nice-to-have packages such as vim or ntp. We try to keep the additional packages at a minimum.

Images

Image	Username	Modified
CentOS-7	cloud-user	yes
CentOS-7-cuda	cloud-user	yes
CentOS-8-Stream	centos	no
CentOS-9-Stream	cloud-user	no
AlmaLinux-8	almalinux	no
AlmaLinux-9	almalinux	no
Ubuntu-22.04	ubuntu	no
Ubuntu-20.04	ubuntu	no
Ubuntu-18.04	ubuntu	no

CentOS-7

CentOS is the community version of Red Hat Enterprise Linux (RHEL). CentOS-7 is the distribution that the Pouta admins are the most accustomed to. This is the second-newest major release of CentOS.

CentOS-7-Cuda

This is the same as CentOS-7 but comes with preinstalled NVIDIA drivers. These are useful in combination with the GPU flavors since you do not need to download the drivers yourself. We try to always have the latest NVIDIA drivers installed, but sometimes we are lagging a bit behind. These images are huge, so you should use the normal CentOS-7 image if you are not using a GPU-flavor VM.

CentOS-8-Stream and CentOS-9-Stream

While CentOS-7 is still actively supported, CentOS-8 has been declared end-of-life in December 2021. The CentOS community is now actively maintaining CentOS-8-Stream and CentOS-9-Stream instead. The key differences lay in the relationship between CentOS and RHEL, especially in how changes, i.e., new packages and updates, are deployed:

• with CentOS-7 RHEL is the upstream branch for CentOS, i.e., changes are first deployed for RHEL and then for CentOS
• with CentOS-8-Stream or CentOS-9-Stream, CentOS is the upstream branch for RHEL, i.e., changes are first deployed for CentOS and then for RHEL

The resulting operating system is thus possibly less stable compared to its previous version. The CentOS community emphasizes that the Stream version is nevertheless extremely close in terms of stability to the corresponding RHEL version and thus recommends using it as a replacement for CentOS-8.

Note that this is the upstream version of the image, i.e., we do not perform any change to the image before making it available on our services. The default username is centos for CentOS-8-Stream and cloud-user for CentOS-9-Stream.

AlmaLinux-8 and AlmaLinux-9

AlmaLinux is a linux distribution created in response to the termination of CentOS-8 project and the fundamental change of CentOS building process, due to which CentOS' traditional stability was impacted. AlmaLinux aims to be fully binary-compatible with RedHat Enterprise Linux, and by doing so the linux distribution effectively takes the role that CentOS used to have before the switch to the -Stream versions. Note that these are the upstream versions of the AlmaLinux images, and their default username is almalinux instead of cloud-user.

Ubuntu-22.04, 20.04 and 18.04 LTS

Some like chocolate, some like strawberry. This is the choice for those that do not want to use CentOS. Note that these are the upstream versions of the Ubuntu images, and their default username is ubuntu instead of cloud-user.

Snowflake images

These images you should probably not use without a really good reason. You might be better off creating your own image

If there any images that you think we should add, do not hesitate to contact Service Desk.

cirros

This is a really small image which can be used to boot an instance really fast. This can be useful for doing tests in Pouta, such as testing if the network works or how fast you can launch an instance. You should not use this for persistent VMs, and you should always delete the instance when you are done with testing. There is very little reason for end-users using this image, and if you are unsure, CentOS and Ubuntu are better choices 99% of the time.

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