Category Archives: linux

Devops, linux

How to check Website status on the Linux Server

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Maintaining website uptime is essential for a positive user experience, as even short periods of downtime can frustrate users and result in lost business. Automating uptime checks on a Linux machine allows quick detection of issues, enabling faster response times. In this article, we’ll explore simple, effective ways to create a Website Uptime Checker Script in Linux using different commands like curl, wget, ping.

As my team and we are worked on windows machines and familiar with PowerShell but now we are working on the Linux based machine which lead to write articles based on command which we are using on daily basis.

1. Checking Website Uptime with curl

One of the most straightforward ways to check if a website is up is by using curl. The following multi-line bash script pings the specified website and returns its status:

#!/bin/bash
website="https://example.com"

# Check if website is accessible
if curl --output /dev/null --silent --head --fail "$website"; then
echo "Website is up."
else
echo "Website is down."
fi

Alternatively, here’s a one-liner with curl:

curl -Is https://dotnet-helpers.com | head -n 1 | grep -q "200 OK" && echo "Website is up." || echo "Website is down."

Explanation:

  • curl -Is sends a HEAD request to retrieve only headers.
  • head -n 1 captures the status line of the HTTP response.
  • grep -q “200 OK” checks if the response is “200 OK”.
    Based on this, the command outputs either “Website is up.” or “Website is down.”

2. Monitoring Uptime with wget

If curl isn’t available, wget can be an alternative. Here’s a multi-line script using wget:

#!/bin/bash
website="https://dotnet-helpers.com"

if wget --spider --quiet "$website"; then
echo "Website is up."
else
echo "Website is down."
fi

And the one-liner version with wget:

wget --spider --quiet https://dotnet-helpers.com && echo "Website is up." || echo "Website is down."

Explanation:

  • The –spider option makes wget operate in “spider” mode, checking if the website exists without downloading content.
  • –quiet suppresses the output.

3. Checking Server Reachability with ping

Although ping checks the server rather than website content, it can still verify server reachability. Here’s a multi-line script using ping:

#!/bin/bash
server="example.com"

if ping -c 1 "$server" &> /dev/null; then
echo "Server is reachable."
else
echo "Server is down."
fi

And here’s the one-liner with ping:

ping -c 1 https://dotnet-helpers.com &> /dev/null && echo "Server is reachable." || echo "Server is down."

Summary

By combining these single-line and multi-line commands, you can monitor website availability, server reachability, and port status effectively. Monitoring website uptime on a Linux machine is simple and effective with these commands. Choose the single-line or multi-line scripts that best suit your needs, and consider automating them for consistent uptime checks. Start implementing these methods to ensure your website remains accessible and reliable for your users.

Devops, linux

Linux Environment Variables

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What Are Linux Environment Variables?

Linux environment variables are dynamic values that the operating system and various applications use to determine information about the user environment. They are essentially variables that can influence the behavior and configuration of processes and programs on a Linux system. These variables are used to pass configuration information to programs and scripts, allowing for flexible and dynamic system management.

These variables, often referred to as global variables, play a crucial role in tailoring the system’s functionality and managing the startup behavior of various applications across the system. On the other hand, local variables are restricted and accessible from within the shell in which they’re created and initialized.

Linux environment variables have a key-value pair structure, separated by an equal (=) sign. Note that the names of the variables are case-sensitive and should be in uppercase for instant identification.

Key Features of Environment Variables

  • Dynamic Values: They can change from session to session and even during the execution of programs.
  • System-Wide or User-Specific: Some variables are set globally and affect all users and processes, while others are specific to individual users.
  • Inheritance: Environment variables can be inherited by child processes from the parent process, making them useful for configuring complex applications.

Common Environment Variables

Here are some commonly used environment variables in Linux:

  • HOME: Indicates the current user’s home directory.
  • PATH: Specifies the directories where the system looks for executable files.
  • USER: Contains the name of the current user.
  • SHELL: Defines the path to the current user’s shell.
  • LANG: Sets the system language and locale settings.

Setting and Using Environment Variables

Temporary Environment Variables

You can set environment variables temporarily in a terminal session using the export command: This command sets an environment variable named MY_VAR to true for the current session. Environment variables are used to store information about the environment in which programs run.

export MY_VAR=true
echo $MY_VAR

Example 1: Setting Single Environment Variable

For example, the following command will set the Java home environment directory.

export JAVA_HOME=/usr/bin/java

Note that you won’t get any response about the success or failure of the command. As a result, if you want to verify that the variable has been properly set, use the echo command.

echo $JAVA_HOME

The echo command will display the value if the variable has been appropriately set. If the variable has no set value, you might not see anything on the screen.

Example 2: Setting Multiple Environment Variables

You can specify multiple values for a multiple variable by separating them with space like this:

<NAME>=<VALUE1> <VALUE2><VALUE3>

export VAR1="value1" VAR2="value2" VAR3="value3"

Example 3: Setting Multiple value for single Environment Variable

You can specify multiple values for a single variable by separating them with colons like this: <NAME>=<VALUE1>:<VALUE2>:<VALUE3>

export PATH="/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin"

The PATH variable contains a list of directories where the system looks for executable files. Multiple directories are separated by colons.

Permanent Environment Variables

To make DOTNET_HOME available system-wide, follow these steps:

This command appends the line MY_VAR=”True” to the /etc/environment file, which is a system-wide configuration file for environment variables. By adding this line, you make the MY_VAR variable available to all users and sessions on the system. The use of sudo ensures that the command has the necessary permissions to modify /etc/environment

Example 1: Setting Single Environment Variable for all USERS

export DOTNET_HOME=true
echo 'DOTNET_HOME="true"' | sudo tee /etc/environment -a

Example 2: Setting Multiple value for single Environment Variable for all USERS

You can specify multiple values for a single variable by separating them with colons like this: <NAME>=<VALUE1>:<VALUE2>:<VALUE3>

export PATH="/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin"
echo PATH="/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin" | sudo tee /etc/environment -a

Breakdown of the Command

echo ‘DOTNET_HOME=”true”‘: This command outputs the string DOTNET_HOME=”/dotnet-helpers/execute”. Essentially, echo is used to display a line of text.

| (Pipe): The pipe symbol | takes the output from the echo command and passes it as input to the next command. In this case, it passes the string DOTNET_HOME=”/dotnet-helpers/execute” to sudo tee.

sudo tee /etc/environment -a: sudo: This command is used to run commands with superuser (root) privileges. Since modifying /etc/environment requires administrative rights, sudo is necessary.

tee: The tee command reads from the standard input (which is the output of the echo command in this case) and writes it to both the standard output (displaying it on the terminal) and a file.

/etc/environment: This is the file where tee will write the output. The /etc/environment file is a system-wide configuration file for environment variables.

-a: The -a (append) option tells tee to append the input to the file rather than overwriting its contents. This ensures that any existing settings in /etc/environment are preserved and the new line is simply added to the end of the file.

This command is used to add a new environment variable (DOTNET_HOME) to the system-wide environment variables file (/etc/environment). By appending it, you ensure that the new variable is available to all users and sessions across the entire system.

Devops, linux

A Step-by-Step Guide to Set Environment Variables in Linux

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What Are Environment Variables in Linux?

Environment Variables in Linux are dynamic values that the operating system and various applications use to determine information about the user environment. They are essentially variables that can influence the behavior and configuration of processes and programs on a Linux system. These variables are used to pass configuration information to programs and scripts, allowing for flexible and dynamic system management.

These variables, often referred to as global variables, play a crucial role in tailoring the system’s functionality and managing the startup behavior of various applications across the system. On the other hand, local variables are restricted and accessible from within the shell in which they’re created and initialized.

Linux environment variables have a key-value pair structure, separated by an equal (=) sign. Note that the names of the variables are case-sensitive and should be in uppercase for instant identification.

Key Features of Environment Variables

  • Dynamic Values: They can change from session to session and even during the execution of programs.
  • System-Wide or User-Specific: Some variables are set globally and affect all users and processes, while others are specific to individual users.
  • Inheritance: Environment variables can be inherited by child processes from the parent process, making them useful for configuring complex applications.

Common Environment Variables

Here are some commonly used environment variables in Linux:

  • HOME: Indicates the current user’s home directory.
  • PATH: Specifies the directories where the system looks for executable files.
  • USER: Contains the name of the current user.
  • SHELL: Defines the path to the current user’s shell.
  • LANG: Sets the system language and locale settings.

Setting and Using Environment Variables

Temporary Environment Variables in Linux

You can set environment variables temporarily in a terminal session using the export command: This command sets an environment variable named MY_VAR to true for the current session. Environment variables are used to store information about the environment in which programs run.

export MY_VAR=true
echo $MY_VAR

Example 1: Setting Single Environment Variable

For example, the following command will set the Java home environment directory.

export JAVA_HOME=/usr/bin/java

Note that you won’t get any response about the success or failure of the command. As a result, if you want to verify that the variable has been properly set, use the echo command.

echo $JAVA_HOME

The echo command will display the value if the variable has been appropriately set. If the variable has no set value, you might not see anything on the screen.

OUTPUT :

Example 2: Setting Multiple Environment Variables

You can specify multiple values for a multiple variable by separating them with space like this:

<NAME>=<VALUE1> <VALUE2><VALUE3>

export VAR1="value1" VAR2="value2" VAR3="value3"

Example 3: Setting Multiple value for single Environment Variable

You can specify multiple values for a single variable by separating them with colons like this: <NAME>=<VALUE1>:<VALUE2>:<VALUE3>

export PATH="/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin"

The PATH variable contains a list of directories where the system looks for executable files. Multiple directories are separated by colons.

Permanent Environment Variables in Linux

To make MY_VAR available system-wide, follow these steps:

This command appends the line MY_VAR=”True” to the /etc/environment file, which is a system-wide configuration file for environment variables.

By adding this line, you make the MY_VAR variable available to all users and sessions on the system.

The use of sudo ensures that the command has the necessary permissions to modify /etc/environment

Example 1: Setting Single Environment Variable for all USERS

export MY_VAR=true
echo 'MY_VAR="true"' | sudo tee /etc/environment -a

Breakdown of the Command

echo ‘MY_VAR=”true”‘: This command outputs the string MY_VAR=”true”. Essentially, echo is used to display a line of text.

| (Pipe): The pipe symbol | takes the output from the echo command and passes it as input to the next command. In this case, it passes the string MY_VAR=”true” to sudo tee.

sudo tee /etc/environment -a: sudo: This command is used to run commands with superuser (root) privileges. Since modifying /etc/environment requires administrative rights, sudo is necessary.

tee: The tee command reads from the standard input (which is the output of the echo command in this case) and writes it to both the standard output (displaying it on the terminal) and a file.

/etc/environment: This is the file where tee will write the output. The /etc/environment file is a system-wide configuration file for environment variables.

-a: The -a (append) option tells tee to append the input to the file rather than overwriting its contents. This ensures that any existing settings in /etc/environment are preserved and the new line is simply added to the end of the file.

This command is used to add a new environment variable (MY_VAR) to the system-wide environment variables file (/etc/environment). By appending it, you ensure that the new variable is available to all users and sessions across the entire system.

Example 2: Setting Multiple value for single Environment Variable for all USERS

You can specify multiple values for a single variable by separating them with colons like this: <NAME>=<VALUE1>:<VALUE2>:<VALUE3>

export MY_PATH="/usr/local/bin:/usr/bin:/bin:/usr/local/sbin"
echo MY_PATH="/usr/local/bin:/usr/bin:/bin:/usr/local/sbin" | sudo tee /etc/environment -a

OUTPUT :