Platform Notes

This page will show you the specific considerations when using an OpenNebula cloud, according to the different supported platforms.

This is the list of the individual platform components that have been through the complete OpenNebula Quality Assurance and Certification Process.

Certified Components Version

Front-End Components

KVM Nodes

LXC Nodes

Linux and Windows Contextualization Packages

Refer to: one-apps release

More information: one-apps wiki

Open Cloud Networking Infrastructure

Open Cloud Storage Infrastructure

Authentication

Monitoring and Backups

Sunstone

Chrome: chrome://flags -> #touch-events: disabled. Firefox: about:config -> dom.w3c_touch_events: disabled.

Certified Infrastructure Scale

A single instance of OpenNebula (i.e., a single oned process) has been stress-tested to cope with 500 hypervisors without performance degradation. This is the maximum recommended configuration for a single instance, and depending on the underlying configuration of storage and networking, it is mainly recommended to switch to a federated scenario for any larger number of hypervisors.

However, there are several OpenNebula users managing significantly higher numbers of hypervisors (to the order of two thousand) with a single instance. This largely depends, as mentioned, on the storage, networking, and also monitoring configuration.

Front-End Platform Notes

The following applies to all Front-Ends:

• XML-RPC tuning parameters (MAX_CONN, MAX_CONN_BACKLOG, KEEPALIVE_TIMEOUT, KEEPALIVE_MAX_CONN and TIMEOUT) are only available with packages distributed by us, as they are compiled with a newer xmlrpc-c library.
• Only Ruby versions >= 2.0 are supported.

Nodes Platform Notes

The following items apply to all distributions:

• When using qcow2 storage drivers you can make sure that the data is written to disk when doing snapshots by setting the cache parameter to writethrough. This change will make writes slower than other cache modes but safer. To do this edit the file /etc/one/vmm_exec/vmm_exec_kvm.conf and change the line for DISK:

DISK = [ driver = "qcow2", cache = "writethrough" ]

• Most Linux distributions using a kernel 5.X (i.e. Debian 11) mount cgroups v2 via systemd natively. If you have hosts with a previous version of the distribution mounting cgroups via fstab or in v1 compatibility mode (i.e. Debian 10) and their libvirt version is <5.5, during the migration of VMs from older hosts to new ones you can experience errors like

WWW MMM DD hh:mm:ss yyyy: MIGRATE: error: Unable to write to '/sys/fs/cgroup/machine.slice/machine-qemu/..../cpu.weight': Numerical result out of range Could not migrate VM_UID to HOST ExitCode: 1

This happens in every single VM migration from a host with the previous OS version to a host with the new one.

To solve this, there are 2 options: Delete the VM and recreate it scheduled in a host with the new OS version or mount cgroups in v1 compatibility mode in the nodes with the new OS version. To do this

1. Edit the bootloader default options (normally under /etc/defaults/grub.conf)
2. Modify the default commandline for the nodes (usually GRUB_CMDLINE_LINUX="...") and add the option systemd.unified_cgroup_hierarchy=0
3. Recreate the grub configuration file (in most cases executing a grub-mkconfig -o /boot/grub/grub.cfg)
4. Reboot the host. The change will be persistent if the kernel is updated

RedHat 8 Platform Notes

Disable PolicyKit for Libvirt

It is recommended that you disable PolicyKit for Libvirt:

$ cat /etc/libvirt/libvirtd.conf
...
auth_unix_ro = "none"
auth_unix_rw = "none"
unix_sock_group = "oneadmin"
unix_sock_ro_perms = "0770"
unix_sock_rw_perms = "0770"
...

AlmaLinux 9 Platform Notes

Disable Libvirtd’s SystemD Socket Activation

OpenNebula currently works only with the legacy livirtd.service. You should disable libvirt’s modular daemons and systemd socket activation for the libvirtd.service. You can take a look at this bug report, for a detailed workaround procedure.

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