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Test API endpoint with netcat

Do you need a simple way to validate that an API endpoint is responsive, but you don't want to use curl?
There is a simple way to validate the endpoint with nc, producing an output that can be redirected to a logfile and parsed later:

URL=$1
PORT=$2

while true; do
    RESULT=$(nc -vz $URL $PORT 2>&1)
    DATE=$(date)
    echo $DATE $RESULT

    sleep 1
done

You can all this script with the API URL as first parameter, and API port as the second.
netcat will be accessing to that endpoint and will report the results, detecting when the API is down. We also can output the date to have a reference when failures are detected.

The produced output will be something like:

vie jun 26 08:19:28 UTC 2020 Ncat: Version 7.70 ( https://nmap.org/ncat ) Ncat: Connected to 192.168.111.3:6443. Ncat: 0 bytes sent, 0 bytes received in 0.01 seconds.
vie jun 26 08:19:29 UTC 2020 Ncat: Version 7.70 ( https://nmap.org/ncat ) Ncat: Connected to 192.168.111.3:6443. Ncat: 0 bytes sent, 0 bytes received in 0.01 se…
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Enable UEFI PXE boot in Supermicro SYS-E200

When provisioning my Supermicro SYS-E200-8D machines (X10 motherboard), i had the need to enable UEFI boot mode, and provision through PXE.
This may seem straightforward, but there is a set of BIOS settings that need to be changed in order to enable it.

First thing is to enable EFI on LAN , and enable Network Stack. To do that, enter into BIOS > Advanced > PCIe/PCI/PnP configuration and check that your settings match the following:


See that PCI-E have EFI firmware loaded. Same for Onboard LAN OPROM and Onboard Video OPROM. And UEFI Network stack is enabled , as well as IPv4 PXE/IPv6 PXE support.

Next thing is to modify boot settings. The usual boot order for PXE is to first add hard disk and second PXE network . The PXE tools (for example Ironic) will set a temporary boot order for PXE (one time) to enable the boot from network, but then the reboot will be done from hard disk. So be sure that your boot order matches the following:


See that the first order is hard disk and second…

Configure and measure realtime workers performance on OpenShift

Depending on your workloads, you may want to have workers with realtime kernel in your cluster.
How to configure and how to enroll the nodes into an Openshift cluster is not on the scope of this article, we will assume that you have the worker node up and running with realtime kernel.
Once you have it, how to properly schedule workloads that make use of it?
CPU manager and kubelet static policy - https://docs.openshift.com/container-platform/4.2/scalability_and_performance/using-cpu-manager.html CPU Manager manages groups of CPUs and constrains workloads to specific CPUs. This is useful for several cases, in our case for low-latency applications. In order to enable CPU manager following steps are needed:
Label a node with cpu manager:
# oc label node perf-node.example.com cpumanager=trueEdit the machineconfigpool worker, and add a label to reference a custom kubelet:
# oc edit machineconfigpool worker metadata: creationTimestamp: 2019-xx-xxx generation: 3 labels: custom-kubelet…

Add RHEL8 nodes to OpenShift deployments

This blogpost is going to show how to automatically enroll RHEL 8 (realtime) to Openshift 4.1 deployments, using UPI method.
This assumes that you will setup an OpenShift cluster using UPI, following the according documentation: https://docs.openshift.com/container-platform/4.1/installing/installing_bare_metal
The procedure on how to spin up this cluster in a semi-automated way is also shown at https://github.com/redhat-nfvpe/upi-rt . This article will assume that you have this UPI cluster up and running.

Enroll RHEL 8 nodes as workers By default, all nodes added into an OpenShift cluster are based on RHCOS. But there are use caes where you may need RHEL nodes. This is the case of RT (real time) nodes, where you need an specific kernel.
This can be achieved with the help of kickstart, and some specific configuration of PXE kernel args (in this case achieved with matchbox).
We are going to use RHEL8 images, booted with PXE, but we are going to add some specific configuration to allow t…

Create and restore external backups of virtual machines with libvirt

A common need for deployments in production, is to have the possibility of taking backups of your working virtual machines, and export them to some external storage.
Although libvirt offers the possibility of taking snapshots and restore them, those snapshots are intended to be managed locally, and are lost when you destroy your virtual machines.
There may be the need to just trash all your environment, and re-create the virtual machines from an external backup, so this article offers a procedure to achieve it.
First step, create an external snapshot So the first step will be taking an snapshot from your running vm. The best way to take an isolated backup is using blockcopy virsh command. So, how to proceed?

1. First you need to extract all the disks that your vm has. This can be achieved with domblklist command:
DISK_NAME=$(virsh domblklist {{domain}} --details | grep 'disk' | awk '{print $3}')

This will extract the name of the device that the vm is using (vda, hda, et…

Setup an NFS client provisioner in Kubernetes

Setup an NFS client provisioner in Kubernetes One of the most common needs when deploying Kubernetes is the ability to use shared storage. While there are several options available, one of the most commons and easier to setup is to use an NFS server.
This post will explain how to setup a dynamic NFS client provisioner on Kubernetes, relying on an existing NFS server on your systems.
Step 1. Setup an NFS server (sample for CentOS) First thing you will need, of course, is to have an NFS server. This can be easily achieved with some easy steps:

Install nfs package: yum install -y nfs-utils Enable and start nfs service and rpcbind:
systemctl enable rpcbind
systemctl enable nfs-server
systemctl start rpcbind
systemctl start nfs-server
Create the directory that will be shared by NFS, and change the permissions:
mkdir /var/nfsshare
chmod -R 755 /var/nfsshare
chown nfsnobody:nfsnobody /var/nfsshare
 Share the NFS directory over the network, creating the /etc/exports file:
vi /etc/exports
/var/nfsshare …