Metacentrum Cloud Documentation
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Frequently Asked Questions

Where I can find how to use MetaCentrum Cloud effectively?

Read our cloud best-practice tips.

What to expect from the cloud and cloud computing

Migration of Legacy Systems to Cloud Computing article gives an overview of what to expect when joining a cloud with a personal legacy application.

What are the cloud computing benefits?

The most visible cloud computing benefits are:

  • cost savings
  • online access to the cloud resources for everyone authorized
  • cloud project scalability (elasticity)
  • online cloud resource management and improved sustainability
  • security and privacy improvements
  • encouraged cloud project agility

How do I register?

Follow instructions for registering in MetaCentrum Cloud.

How do I migrate from legacy platforms?

Follow instructions for migrating from CESNET-MetaCloud or OStack ICS MUNI.

Where do I report a problem?

First, try searching the documentation for an answer to your problem. If that does not yield results, open a ticket with When contacting user support, always include your username (upper right corner of the web interface) and domain with active project (upper left corner of the web interface) as well as a description of your problem and/or an error message if available.

What networks I can use to access my instances?

Personal projects can allocate floating IPs from public-muni-147-251-124 and private-muni-10-16-116. Group projects can currently allocate floating IPs from public-cesnet-78-128-251 and private-muni-10-16-116. IP addresses from public-muni-147-251-124 allocated by users to group projects are released daily, so we encourage using only public-cesnet-78-128-251 and private-muni-10-16-116 for group projects. Follow instructions at changing the external network in order to change your public network.

Issues with network stability in Docker

OpenStack instances use 1442 bytes MTU (maximum transmission unit) instead of standard 1500 bytes MTU. The instance itself can set up correct MTU with its counterpart via Path MTU Discovery. Docker needs MTU set up explicitly. Refer documentation for setting up 1442 MTU in Docker or Kubernetes.

Issues with proxy in private networks

OpenStack instances can either use public or private networks. If you are using a private network and you need to access the internet for updates etc., you can use muni proxy server This server only supports HTTP protocol, not HTTPS. To configure it you must also consider what applications will be using it because they can have their configuration files, where this information must be set. If so, you must find the particular setting and set up there mentioned proxy server with port 3128. Most applications use the following setting, which can be done by editing file /etc/environment where you need to add a line http_proxy="". And then you must either restart your machine or use the command source /etc/environment.

How many floating IPs does my group project need?

One floating IP per project should generally suffice. All OpenStack instances are deployed on top of internal OpenStack networks. These internal networks are not by default accessible from outside of OpenStack, but instances on top of the same internal network can communicate with each other.

To access the internet from an instance, or access an instance from the internet, you could allocate floating public IP per instance. Since there are not many public IP addresses available and assigning public IP to every instance is not a security best practice, both in public and private clouds these two concepts are used:

  • internet access is provided by virtual router - all new OpenStack projects are created with group-project-network internal network connected to a virtual router with public IP as a gateway. Every instance created with group-project-network can access the internet through NAT provided by its router by default.
  • accessing the instances:
  • I need to access instances by myself - best practice for accessing your instances is creating one server with floating IP called jump host and then access all other instances through this host. Simple setup:
    1. Create an instance with any Linux.
    2. Associate floating IP with this instance.
    3. Install sshuttle on your client.
    4. sshuttle -r root@jump_host_fip All your traffic to the internal OpenStack network is now tunneled through the jump host.
  • I need to serve content (e.g. web service) to other users - public and private clouds provide LBaaS (Load-Balancer-as-a-Service) service, which proxies users traffic to instances. MetaCentrum Cloud provides this service in experimental mode - documentation

In case, that these options are not suitable for your use case, you can still request multiple floating IPs.

I can’t log into OpenStack, how is that possible?

The most common reason why you can’t log into your OpenStack account is that your membership in Metacentrum has expired. To extend your membership in Metacentrum, you can visit