Among 3 million public IP address ranges for the whole world, 68k belongs to the Russian Federation. This translates into 45 million addresses. Scanning the HTTP port on this population took 20 hours. I obtained 630k IP addresses with listening on port 80. Of which 530k gives the correct answer of the HTTP type. Only 340k gives an HTTP 200 response. Over 200k run on NGINX servers, and 100k run on Apache. When analyzing the content, you will find GitLab, Kibana, Zabbix or Grafana installations open for registration and use, but also copies of databases, video surveillance systems, etc. My
The basis for the construction of diodes and transistors A semiconductor is a material whose electrical conductivity is between the conductors and insulators. Their resistance and conductivity depends on temperature and admixtures. [W] The most commercially used semiconductors are those based on silicon, and in the past also on germanium. In addition to these two elements (in crystalline form), a whole spectrum of other substances from groups 13-15 is used, which can form two, three or four-element compounds. P-n junction The basic element of a semiconductor system [003] Additions of atoms of other elements are used to obtain the increased
Energy in a magnetic field [209] Just as a capacitor works by storing energy as an electric field, an inductor stores energy as a magnetic field. The energy stored in the coil is calculated in terms of current. The capacitor acts as an insulator of the circuit while the inductor acts as its conductor. The coils have inductance expressed in henry [H]. The coils are plugged into the circuit in series with the powered device. The coils are characterized by a maximum current, as their windings have a certain resistance, therefore the flow of current causes a voltage to accumulate
I will start with the werid experience with one of WP themes – Polite and Polite Grid. I was wondering why my website make double requests on every page. One for the document and other for content. This was annoying as I was unable to measure traffic properly. It turned out that it was because of the theme I’ve been using for some time. Changing it to different one fixed it. Second of all to make NGINX logs easier to handle I’ve created separate location entry for all the WP things, so the “real” traffic goes only to particular log
Lowering the voltage value [202] The next example I want to present in practice is a popular voltage divider. It allows the output voltage to be reduced to the desired value due to the properties described a little earlier. Bearing in mind the above formula, we can assume that we want to reduce the input voltage of 5V to the expected 2.5V at the output. So we use two 1K resistors connected in series. Examples available at https://github.com/michalasobczak/simple_hpc/tree/master/SeriesPartOne
Theory and practice [W] One of the basic principles of current flow is the first law of Kirchhoff, which says that for the electric circuit node, the algebraic sum of flow rates is zero. The sum of currents flowing into the node is equal to the sum of currents flowing out of this node. This law results from the principle of keeping the load. Kirchhoff’s second law says that the sum of voltage drops in a closed circuit is zero, assuming that the voltage drop is its negative increase. [202] For the purposes of illustrating the law of Kirchhoff, I
Signal filtering [202] Capacitors are divided into polarized and non-polarized depending on whether the direction of their inclusion in the circuit is important. Generally speaking, capacitors filter the waveform of the power source. It is assumed that the longer lead from the capacitor is the positive pole, which is sometimes reflected in the marking in the diagram. Electrolytic capacitors consist of a metal cover and an electrolyte lined with paper. Non-polar (non-polarized) capacitors can be made of ceramic elements or foil. There are also tantalum capacitors which both offer high capacitance and relatively low losses. The physical size of a
In case you’ve managed to overcome other issues with system unable to boot, disk size not updated then there might be still one problem left. Sometimes resizing with gpart works fine but file system resize does not. I’ve encountered such issue and frankly speaking I’m not quite sure what is root cause of it. Is says that file system is dirty and I should run fsck which can be executed from console selecting number 5 and then F letter. System reboots and makes file system check. It says that the file system is fine, so it’s quite confusing. Solution for
Following previous struggles on pfSense FreeBSD on Azure. After resizing disk Microsoft starts at some point adding an another drive which is temporary one. I do not need this by any means. It seems that NetGate pfSense template is also not quite compatible with cloud-init as the platform tries to execute systemctl which is not present here. The problem with this is that FreeBSD will not be able to pick which partition it should start from. Fix for this is pretty simple. Just go and edit /etc/fstab and instead of pointing to some virtual labels. In my case it was