When VM resizing or cold migrating between hypervisors, it’s highly probable that you will come across an SSH error indicating “Permission denied” as below in /var/log/nova/nova-compute.log of host that is running the instance for cold migration. ERROR oslo_messaging.rpc.server Traceback (most recent call last): ERROR oslo_messaging.rpc.server File “/usr/lib/python2.7/site-packages/oslo_messaging/rpc/server.py”, line 165, in…

I hope you know that OpenStack, offers a valuable feature called “live migration” that allows to move virtual machines (VMs) from one physical host to another without causing downtime. It is an essential capability for maintaining high availability and optimizing resource usage in cloud environments. However, while configuring and performing…

Customize OpenStack Horizon Dashboard allows you to tailor the interface to your specific needs and preferences such as its appearance, including logos, colors, and styles, to match the organization’s branding. Let’s dive into start rebrand OpenStack Horizon dashboard. How to customize OpenStack Horizon Dashboard? Following guide will help to customize…

  Mitigate Clickjacking or UI redressing in a WordPress website involves implementing security measures to prevent attackers from embedding your site’s content into malicious iframes or manipulating the user interface.   How to test Clickjacking? Create a test.html file on your desktop with following contents and access it through the…

If you are running WordPress on your website then you should follow this article to prevent a DoS attack in WordPress because of the load-scripts.php file which concatenates JS files on the fly. Barak Tawily in his blog post clearly explains the WordPress vulnerability to DoS attack which is through…

On my OpenStack setup with 2-nodes, 1-controller+compute and 1-compute node, I got the error message “No valid host was found. No valid host found for resize” during resize of a VM. Below are the detailed message in nova-api.log nova-scheduler.log & nova-conductor.log: # vim /var/log/nova/nova-api.log 2023-03-23 10:45:19.441 3219 INFO nova.api.openstack.wsgi [req-4d2542f9-38f4-4900-88d9-b1c987651ebf…

While installing Kubernetes and configuring Kubernetes on the Master node, encountered the error “failed to pull image registry.k8s.io/kube-apiserver:v1.27.1”. Below is the complete error message: # kubeadm config images pull failed to pull image “registry.k8s.io/kube-apiserver:v1.27.1″: output: time=”2023-07-19T05:36:01Z” level=fatal msg=”validate service connection: CRI v1 image API is not implemented for endpoint \”unix:///var/run/containerd/containerd.sock\”:…

Since my webserver (apache) wasn’t responding, I restarted the apache service. Most of the time restarting works, this time it didn’t! The error message was “No space left on device: Couldn’t create the rewrite-map mutex: Configuration Failed”. Let’s try to diagnose the issue and find the solution. Analyse why Apache restart…

When developing a WordPress plugin, it’s a good practice to refer relative file names while referring assets (Image, css etc.,) or perform tasks such as Ajax request in JavaScript files. Relative file paths in JavaScript typically refer to files located within the plugin’s directory. In my case I need to…

After fixing undefined function mb_internal_encoding encountered an another error “Uncaught Error: Class DOMImplementation not found“. Below is the complete error: Error: [Fri Jun 16 11:07:04.798269 2023] [php7:error] [pid 820060] [client techglimpse.com:21132] PHP Fatal error: Uncaught Error: Class ‘DOMImplementation’ not found in /var/www/html/wordpress/wp-content/plugins/pdfgenerate/dompdf/vendor/masterminds/html5/src/HTML5/Parser/DOMTreeBuilder.php:172\nStack trace:\n#0 /var/www/html/wordpress/wp-content/plugins/pdfgenerate/dompdf/vendor/masterminds/html5/src/HTML5.php(157): Masterminds\\HTML5\\Parser\\DOMTreeBuilder->__construct()\n#1 /var/www/html/wordpress/wp-content/plugins/pdfgenerate/dompdf/vendor/masterminds/html5/src/HTML5.php(89): Masterminds\\HTML5->parse()\n#2 /var/www/html/wordpress/wp-content/plugins/pdfgenerate/dompdf/vendor/dompdf/dompdf/src/Dompdf.php(478): Masterminds\\HTML5->loadHTML()\n#3 /var/www/html/wordpress/wp-content/plugins/pdfgenerate/formprocess.php(143):…

Recently in one of my web development project, I tried to use Dompdf and encountered error “Call to undefined function mb_internal_encoding() [DomPDF]“. Error: [Fri Jun 16 10:30:49.244911 2023] [php7:error] [pid 819590] [client techglimpse.com:19416] PHP Fatal error: Uncaught Error: Call to undefined function Dompdf\\mb_internal_encoding() in /var/www/html/wordpress/wp-content/plugins/pdfgenerate/dompdf/vendor/dompdf/dompdf/src/Dompdf.php:295\nStack trace:\n#0 /var/www/html/wordpress/wp-content/plugins/pdfgenerate/dompdf/vendor/dompdf/dompdf/src/Dompdf.php(269): Dompdf\\Dompdf->setPhpConfig()\n#1 /var/www/html/wordpress/wp-content/plugins/pdfgenerate/formprocess.php(139): Dompdf\\Dompdf->__construct()\n#2…

Recently some of the virtual machines used for my developmental activities were attacked! The problem was that there was a process (with random alpha-numeric characters) that fills up the CPU and even if it is killed, it will re-occur after some time 🙁 Let’s try to detect and analyse botnet…

Followed your article to create a Windows Image for OpenStack glance repository. After successfully booting of VM, found the size of the qcow2 image is 20GiB. # ls -lrth win10.qcow2 -rw——-. 1 qemu qemu 21G Dec 9 13:45 win10.qcow2 However, there is a lot of free space available on the…

My system administrator installed minimal CentOS server and forgotten to setup the hostname. Now it has localhost.localadmin. How would I change the hostname on CentOS? Solution: A computer hostname represents a unique name that identifies a machine on a network. You need follow few rules in setting up the hostname:…

Thanks to this article – how to create a Windows Image for OpenStack Glance repository.  After uploading the image, I created a separate flavor for Windows VMs with 2 vCPUs, 4GB RAM, and 40GB disk. However, when the Windows VM is booted, I noticed the hard disk space of 20GB,…

While installing pip packages through the requirements file on the minimal CentOS Stream 8 server with python v3.7, encountered the error “No such file or directory c++” during the installation of grpcio package. Below is the complete error message: # pip3 install -r requirements.txt WARNING: Running pip install with root…

Followed the guide from server-world for installing the OpenStack Train version on the CentOS server. Configuring neutron services requires physical access to the terminal, as it requires a restart of the network services. But sometimes, you don’t get to be present in front of the physical terminal and end up…

While finalizing the installation of neutron on controller node, the operation to populate the database failed with Too many connections for neutron-db-manage. Below is the complete error: # su -s /bin/bash neutron -c “neutron-db-manage –config-file /etc/neutron/neutron.conf –config-file /etc/neutron/plugins/ml2/ml2_conf.ini upgrade head” Traceback (most recent call last): File “/usr/bin/neutron-db-manage”, line 10, in…

On my CentOS 7 minimal server installation, I installed python-pip using YUM. However, the version it has installed is 8.1.2 for Python version 2.7 though the latest version is 22.3.1. Some of the packages needs a higher version of pip atleast above 9.0.1. When tried to upgrade using pip install…