Common issues

This article provides solutions to the most common issues you may have when using VMmanager OVZ.

Issues with control panel

What units of measure are used in a control panel?

the control panel uses KiB and MiB

• KiB (kibibyte) 2¹⁰= 1024;
• MiB (mebibyte) 2²⁰ = 1048576.

How do they differ from KB and MB?:

• MB (megabyte) 10⁶ = 1000000;
• KB (kilobyte) 10³ = 1000.

How to create a virtual machine using MB and GB:

• If you want to create a virtual machine with 2Gb of RAM, enter 1907MiB in the VM creation form (the more exact value is 2GB = 1907,35MiB);
• If you want to create a virtual machine with 15GB of HDD, enter 14305Mib;
• How to calculate units of measure.

When switching between VMmanager OVZ into ISPmanager the browser redirects you to https://__IP__:1500/ispmgr

Make sure that the correct path for ihttpd start is specified inside the container in  /etc/rc.local.

Issues with cluster nodes

Cannot add a cluster node with CentOS

Possible issue — required packages are not installed. The cause of the issue  — the epel repository is not connected.  Possible issue — invalid data on the server — the repository cannot be found. Check and correct the date and time and try again. 

Cluster management utilities

Execute commands on all cluster nodes: 

/usr/local/mgr5/sbin/nodectl --op exec --target all --cmd 'echo "Hello, world!"'

Go to a cluster node via SSH:

/usr/local/mgr5/sbin/nodectl login <cluster node id>

View a list of cluster nodes: 

/usr/local/mgr5/sbin/nodectl list

How to update CentOS correctly

Add exclude=kernel in /etc/yum.conf file. This will block installation/updating of all the packages starting with the kernel. After that, you can start updating. Before this you can execute yum check-update, just to make sure these packages will not be updated.

On some system when using ploop, the insufficient space error message may occur (the error message "No space left on device" is displayed while trying to create a container in the console).

This is the OpenVz bug. A possible solution is to execute the following commands:

echo 0 > /sys/module/ploop/parameters/root_threshold
echo 0 > /sys/module/ploop/parameters/user_threshold

Issues with virtual machines

Error creating a virtual machine: "ERROR: Exception 1: Insufficient RAM for VM creation", therefore Swap has sufficient RAM

Free RAM = free + cached. Swap is not counted.

Cannot create the virtual machine<vm name>: the backup process in progress

If the backup process is running in the control panel and the virtual machine is in the list for backup, all the operations with such a machine will be blocked unless the backup process is over.

Failed to reinstall the OS: the error error_code_7 (no message found) occurred while installing the operating system on 'vm1' (cluster node 'node1')

Make sure that enough resources are allocated to the virtual container. Very often this error is caused by insufficient file descriptors.

Error migrating containers with the simfs file system and active second- level disk quota. VMmanager OVZ generates the warning:  "While migrating the '...' container on the '...' cluster node the error occurred. Error: 'EXIT_QUOTA: Quota operation error.'" 

The second-level disk quota allows setting limits for users and groups inside containers. The only solution is to disable quota for the container. To do so, complete the following steps: 

1. Execute the command: 

   vzctl set CTID --diskquota no --save

2. Restart the container:

   vzctl restart CTID

Once you are done, migrate to another cluster node. Once migration is complete, you may set quotas:

1. Execute the command: 

   vzctl set CTID --diskquota yes --save

2. Restart the container

   vzctl restart CTID