Month: August 2022

technology

Proxmox’s nesting setting with WordPress container

If you happen to use Proxmox’s LXC which stands for Linux Containers, then you might be interested in this one. Proxmox has this turnkey containers available to download from its UI. Among them there is WordPress. If you create a container using template then while creating remember to select nesting=on, because without this it will show permission denied on starting Apache2. Not quite familiar with nesting option but it is necessary to run this container.

technology

Installing PostgreSQL 14 on CentOS 7

PostgreSQL 14 has few improvements over previous versions, especially older ones, like 9.6. This includes automatic data direction using partitioning. So, let’s install it on CentOS 7. Then you should login to the database and set password: Basic configuration includes firewall setup (if it’s active), access control and performance settings: I strongly recommend visiting pgtune.leopard.in.ua for tuning parameters. Last thing is to set interface address on which server will be listening, it’s set in: Now you are good to go.

technology

Ohm’s law

Theory and practice [204] This is the SI unit of resistance. 1 ohm is the electrical resistance between two points on a conductor when a constant potential difference of one volt between the two points causes a current of one ampere in the conductor. Most, if not all, components have internal resistance, such as batteries. It is not a property that is easily measurable. Circuits intended to show some principles assume that, for example, the power source is an ideal cell and any internal resistances are compensated by additional components of such a circuit, assuming a certain margin of error.

technology

Circuit simulation

Construction and testing of circuits in the TINA TI program To translate theory into practice, we can use the TINA package from DesignSoft for Texas Instruments. It is a tool for building virtual analog and digital circuits. The basic version provides the minimum necessary set of elements that can be arranged in the form of a circuit. However, the most important function (at least for me) is the ability to run simulations. All presented examples of simulations are prepared in TINA TI V9 (Schematic Editor), Special Complementary Basic Edition available free of charge. The schema sources are in the repository

technology

Electric voltage

Measure of the strength of electric charges. Electrostatic potential difference. Electronics is based on physics. The basic concepts here are voltage, current and resistance. We should start with that. The voltage is therefore a measure of the strength of electric charges. The voltage between two points of an electric circuit or electric field is the difference in electrostatic potential between these points. We measure voltage in volts. We use a voltmeter to measure the voltage. We always measure voltage between two points because it is a potential difference. The voltage can be constant, variable, alternating. Why we use a given

technology

Recovering Elasticsearch 7 after power outage

In case you encounted power outage or just blindly pressed restart button on your machine, there is high chance you will have some issues with your cluster. Mine has only one node, so there is no redundancy. If I lose indices then data is gone. Fortunately starting Elasticsearch and having red indicators not necessarily means data lose. I recently went that path. Log says that primary shards was missing. In such case you need to check if there are those indices listed: With that command look for red statuses. Internal mechanisms have this delay rule, so check every minute if

technology

Install qemu-guest-agent with Ansible on Proxmox 7.2

I already have over 10 virtual machines in my home virtual environment. It is the number I find enough to start using some automation tools like Ansible. Installing Ansible on Ubuntu or CentOS systems is straightforward, just use regular apt or yum commands. With Ansible you can use commands or create scripts. First you should start with hosts definition file which by default is located at /etc/ansible/hosts. You can use different hosts file but then you need to point it while running commands. This one is default, so no need to do anything special here. Now going quickly to Proxmox’s

technology

Trapping ctrl+c in Bash scripts

If you happen to have some Bash scripts and would like to abort it in clean way there is way to do it. You need to trap ctrl+c command. In case you have some while loop in your scripts, without it, pressing any abort commands is only half way effective. Now, with ctrl+c trapped, you can cleanly abort your script without things still running.

technology

Installing Metricbeat 7.17 agent on Ubuntu

Once you have installed Elasticsearch and Kibana servers you need to grab some data. First choice could be beats modules, either Metricbeat or Packetbeat. There is also Filebeat. Altough installation instructions are available at https://www.elastic.co/guide/en/beats/metricbeat/7.17/metricbeat-installation-configuration.html I found it useful to describe it separately as this page might just disappear out of a sudden. After installation you need to change the configuration file at: Change Kibana and Elasticsearch output addresses. Then start the agent: In case this is the first time you are installing the agent against this particular Elasticsearch server you need to load visualizations and dashboard definitions: Now you’re

WordPress Appliance - Powered by TurnKey Linux