Linux Crontab Tutorial

Crontab Introduction

A daemon’s name is Cron. Daemons are utility programs in Linux that operate in the background, monitoring and carrying out activities in response to triggering events and programmed schedules. Daemons can also be used to automate repetitive tasks.

The origin of the term “cron” can be traced back to the Greek word “Chronos,” which can be translated as “time.” Cron is a daemon that operates according to a set timetable or calendar, as this indicates.

A long-running piece of software known as the cron daemon is a system tool responsible for executing commands at specific dates and times. When using cron daemons, you can schedule computer activities as one-time events, occasional events, or as jobs that are scheduled repeatedly and on a regular basis.

Cron scheduling is useful for many businesses because it can automate repetitive operations, edit databases, data, or files, send bulk email messages, and conduct administrative tasks on a predetermined schedule.

The scheduling syntax that cron utilizes is also often used by software that does not run on operating systems. An example is Zuar’s Mitto data pipeline solution. Mitto can automate a wide range of processes by utilizing cron scheduling, including manipulating data within data warehouses, pulling data from other software, and many more.

The term ‘Cron Table’ can be abbreviated to ‘Crontab,’ a component of Cron. It is a file containing the cron schedule that needs to be executed and the commands used to automate operations and activities. When you make a new cron job, its information will be saved in the crontab file.
System administrators can only modify the system crontab file. However, many administrators are supported by Unix-like operating systems. Everybody can make a crontab file and add commands to it anytime.

Users may automate system upkeep, disk space monitoring, and backup scheduling with cron jobs. Cron jobs are ideal for servers and other machines that operate continuously because of their nature.

Cron jobs can be useful for web developers even though system administrators often utilize them.

As a website administrator, you could, for instance, set up three cron jobs: one to check for broken links every Monday at midnight, one to back up your site every day at midnight automatically, and one to delete the cache of your site every Friday at noon. (more…)

Backup and restore GPG keys on Linux

Introduction

The issue of privacy is becoming more and more controversial. Users of Linux can encrypt files with public-key cryptography by using the gpg command. If you were to lose your encryption keys, this would be a disastrous situation. This is how you may support their claims.

OpenPGP and GNU Privacy Guard

One benefit of electronic files over paper hard copies is the ability to encrypt them so that only authorized users may access them. It won’t matter if they end up in the wrong hands. The contents of the files are only accessible to you and the intended recipient.

(more…)

How to Install and use Monit on Linux

Introduction

In UNIX/Linux-based systems, Monit is a free, open-source tool that automatically manages processes, files, directories, checksums, permissions, filesystems, and services like Apache, Nginx, MySQL, FTP, SSH, SMTP, and others. It also gives system administrators excellent and practical monitoring functionality.

A native HTTP(S) web server or the command line interface can be used to immediately view the system status and setup procedures via the monit’s user-friendly web interfaces web server, such as Apache or Nginx, must be installed on your system in order to access and view the Monit web interface. (more…)

Monitor Linux CPU temperature using s-ui

What is s-tui?

“s-tui” is a terminal utility that runs GNU/Linux and is made to stress test and monitor our CPU. It is a program that graphically displays the frequency of CPU temperature utilization and power consumption without needing an X server. It was created by Alex Manuskin and is written in Python.

An effective way to determine whether a cooling system is working well or whether we have a stable overclock is to run a stress test on a computer. S-tui makes it simple to identify overheating when you see a decrease in frequency. Additionally, it will display any signs of decreased performance.

We can use the tool over SSH because it operates in the terminal. This is helpful if you enjoy using the terminal or for monitoring servers or small PCs like Raspberry Pi.

S-tui does not display precise information about the active processes in the system, which is one drawback of this tool. Just imagine the overall scene. S-tui won’t be of assistance if we’re searching for a tool that provides us with details about specific processes or allows us to manage these processes.

Install s-tui on Ubuntu using the PPA

The installer can also be downloaded and installed for Ubuntu systems using pip or a PPA. We merely need to launch a terminal (Ctrl + Alt + T) and enter the following commands to install s-tui from the PPA:

sudo add-apt-repository ppa:amanusk/python-s-tui && sudo apt update && sudo apt install python-s-tui

To start the program, we need to type “s-tui” in the terminal.

By adding stress, we can expand the program’s alternatives. This package allows us to run the stress test. Although installing this program is not required, it performs excellently. To accomplish this, using the terminal, we type:

sudo apt install stress

Archlinux users:

Use the Pacman command to install the pip package for Archlinux users.

sudo pacman -S python-pip stress

Fedora users:

sudo dnf install python-pip stress

For CentOS/RHEL users:

sudo yum install python-pip stress

For openSUSE users:

sudo zypper install python-pip stress

Stress can be used to highlight the CPU. All the graphs will advance to their maximum values if we choose this mode of operation.
Finally, use the pip command below to install the s-tui utility on Linux:

For Python 2.x:

sudo pip install s-tui

For Python 3.x:

sudo pip3 install s-tui

Getting to S-TUI

The article’s introduction stated as much. To obtain all the information from your system, root privilege is required. To start s-tui, simply enter the following command.

sudo s-tui

By default, it activates hardware monitoring and chooses the “Stress” option to put your system through a stress test.
Go to the help page to see alternative possibilities.

s-tui --help

5 Best Practices to Prevent SSH Brute-Force Login Attacks in Linux

Introduction

Typically, SSH-enabled servers make for easy targets for brute-force attacks. The ongoing development further increases the risk of intrusion by hackers of new software tools and bots for automating brute-force attacks.

This manual will look at strategies to protect your SSH servers from brute-force attacks on Linux distributions based on RHEL and Debian derivatives.

1. Disable SSH Password Authentication and Enable SSH-Key Authentication

Username/password authentication is the standard authentication technique for SSH. But as we have seen, brute-force attacks can be used to target password authentication systems. Implementing key-based SSH authentication, in which authentication is made possible via public and private SSH key pairs, is advised to be safe. While the public key is copied to the server, the client’s private key stays on their computer.

During SSH key authentication, the server verifies whether the client PC has the private key. A shell session is created, or the command supplied to the remote server is executed if the check is successful. You may find detailed instructions for configuring SSH key-based authentication on our website. (more…)

How to Analyze and Optimize MySQL performance

Introduction

MySQL is an open-source relational database that many users prefer to use in their daily operations because of the diversity of storage engines it supports, its flexibility and high performance, robust data security, cost-effectiveness, ease of maintenance, and reliability.

Why should MySQL performance be measured and monitored?

Ensuring smooth and effective database performance is one of the most important features of any organization or company, large or small. Thus, in some cases, having a complete understanding of database uptime or load is crucial and should be monitored frequently.

As a result, numerous monitoring tools are available on the market to track, analyze, and measure performance, as well as examine potential difficulties. They help you optimize queries and visualize database metrics, collect statistics, and present the performance status so that you can understand the influence on overall performance and potential issues that need to be troubleshot.
The following advantages may emerge from optimizing database performance: (more…)

Setup Secure FTP server on Linux using VSFTPD

Introduction

Have you ever worked away from home and realized that you left a critical document on your computer? The optimal method is to utilize an FTP server such as Very Secure FTP Daemon (VSFTPD).
You can install and configure an FTP server using VSFTPD on your Linux server by following the steps in this guide. With this server, you can safely transfer files to other computers.

Continue reading, and you’ll never have to worry about your files being held hostage on your home computer again!
The File Transfer Protocol, sometimes known as FTP, is a standard network protocol that sends and receives data to and from remote networks. Linux users have access to various open-source FTP servers to choose from. PureFTPd, ProFTPD, and vsftpd are the ones that have the most notoriety and are utilized the most frequently. We will install vsftpd (Very Secure FTP Daemon), a dependable, secure, and quick FTP server. In addition, we will demonstrate how to configure the server so that users can only access their home directories and the entire transmission is encrypted using SSL/TLS.

Although FTP is a highly used protocol, you should consider using SCP or SFTP instead if you want to transfer data in a more protected and expedient manner.
In this blog, we will use Ubuntu and similar Debian base distribution; however, any other Linux distribution should also work. (more…)

How to install and use Cacti on Ubuntu 20.04

What is Cacti

The following features are offered by Cacti, a comprehensive network graphing solution created to maximize the potential of RRDtool’s data storage and graphing functionality:

  • Remote and local data collectors
  • gadget discovery
  • generation of devices and graphs automatically
  • Device and graph tagging
  • individual data gathering techniques
  • Controls over the user, group, and domain access

All of this is contained inside a simple interface that is both intuitive and easy to use and is appropriate for both small LAN installations and extensive networks with hundreds of connected devices.

Ian Berry created it as a high school project in the early 2000s. Hundreds of businesses and enthusiasts have used it to monitor and manage their enterprise networks and data centers.

Suppose you see any issues referencing missing tables or columns in the database, whether you are working with the source code or downloading the code directly from the repository. In that case, you must perform the database upgrade script. (more…)

Top Linux GPU monitoring and Diagnostic Tools

Introduction

The components shown on a computer monitor are controlled by a specialized circuit board known as a video card. It is also known as a graphics processing unit or GPU and is responsible for calculating 3D visuals and pictures for use in Linux gaming and other applications. Let’s have a look at the best Linux command-line tools for GPU monitoring and diagnostics so we can fix this problem.
There is a possibility that a graphical processing unit (GPU), often called a video or graphics card, could be present on a Linux machine. Active graphics card monitoring and control can be necessary for various contexts, including mining cryptocurrencies, operating gaming servers, or improving the user experience on a desktop computer.

GPU monitoring and Diagnostic Tools

lshw -C display -short

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Using Windows ipconfig Command

Introduction

The ipconfig command updates DHCP and DNS settings and displays details about your network configuration. The ipconfig command by default shows the default gateway, subnet mask, and IP address. However, you may extract much more information from it with the right parameters.
The ipconfig command and its various options will be explained in this article.

How to Open Command Prompt

You must open the Command Prompt window in order to use this tool. The Command Prompt window can be opened in one of three ways:

  1. Use the Windows search feature to look for “cmd.”
  2. Right-click the Start button and choose Command Prompt.
  3. Press WinKey + R on your keyboard, and then type cmd in the Run window.

How to use the ipconfig command

So, let us start with something easy, like how to use the ipconfig command.
After CMD is opened. Type:

ipconfig

This will show you the most basic information about your network from your network adapters.

ipconfig command

As you can see from the above screenshot, the Command will tell you about each network adapter on your computer. In this case, we have a wired (ethernet) network adapter and a wireless (Wi-Fi) network adapter. If you have a VPN client, it will also show up as a network adapter.

all Option

The Command displays only the most basic network information without using any parameters. But by default, no information on the DNS and DHCP servers is shown. You must use the /all argument to display all the details about your network adapter.

ipconfig /all

The following details will be returned for each network adapter in your device:

ipconfig options

ipconfig output

The ipconfig /all tool is frequently used to diagnose issues with network connections.

release Option

The ipconfig command can reset or update your network settings and display information about your configuration. You can ask the DHCP server for a new IP address if DHCP is enabled on your network card.
To start, the current IP address must be made public. Doing this will let the DHCP server know that we no longer want to use the provided IP Address.

ipconfig /release

ipconfig release

The Command will, by default, release the IP addresses for every network interface. Additionally, a single network adapter may be specified. It would help if you input the name of the adapter that you see here in the output of ipconfig in order to accomplish this:

ipconfig /release Wireless*

ipconfig wireless

renew Option

After releasing an IP Address, a new one must be requested from the DHCP server. This is possible using the Ipconfig /renew Command:

ipconfig /renew

If the renewal was successful, you would receive the same output as the ipconfig command, which includes an overview of your new IP Address, subnet mask, and gateway.
Once more, we can specify a single network adapter by providing the adapter’s name.

ipconfig /renew Wireless*

Display DNS Command

Your computer maintains a local cache of all visited DNS records. This cache quickly translates domain names to their corresponding IP addresses. This eliminates the need for your computer to contact the DNS server each time you visit Google.com, for example:
You can perform the command ipconfig /displaydns to view the DNS cache’s contents.
This will display each DNS record in the DNS cache:

ipconfig /displaydns

ipconfig display dns

Flush DNS Command

Occasionally, your DNS Cache may contain obsolete records, resulting in DNS-related errors (unable to reach websites, for example). Typically, this can be resolved by executing the flush DNS Command.

ipconfig /flushdns

The ipconfig /flushdns command clears your DNS Cache. This is risk-free; your computer will simply request updated DNS records from the DNS servers.

 

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