Monitoring the activity of users on a Linux system is an important aspect of system administration. By keeping track of how long a particular user has been connected, we can gain valuable insights into their usage patterns and identify any irregularities or potential security issues. Thankfully, the <code>ac</code> command in Linux provides a straightforward way to obtain this information.
To print how long a specific user has been connected in hours per day, we can use the <code>-p</code> option followed by the username. This will display a daily summary of the user's activity, including the number of hours they have been actively connected.
<pre><code class="language-bash">ac -p username
</code></pre>
The output will include a table with columns for the date, the total hours the user was logged in, and the average number of hours per login. This information can be particularly useful in understanding how much time a user spends on the system on a daily basis.
<pre><code> | total | min | avg | max | nlogins
DATE | HOURS | TIME | TIME | TIME | COUNT
YYYY-MM-DD | aaaaaaaa | | aaaaaa | aaaaaa | aaaaaaa
YYYY-MM-DD | aaaaaaaa | | aaaaaa | aaaaaa | aaaaaaa
</code></pre>
To calculate the total number of hours the user has been connected in a specific period, you can iterate through the output and sum up the hours for each day. This way, you will obtain the overall usage statistics for that particular user.
Using the <code>ac</code> command simplifies the process of tracking user activity and enables system administrators to keep a close eye on how users are utilizing the system. By having this information readily available, administrators can identify potential security risks, monitor resource usage, and mitigate any unauthorized access attempts.
So next time you need to investigate how long a specific user has been connected to a Linux system, remember to utilize the power of the <code>ac</code> command. Keep an eye on user activity, ensure optimal system performance, and maintain a secure environment.
Happy administering!

linux ac: Print how long a particular user has been connected in hours per day (with total)

Linux Addr2line
Introduction
When it comes to debugging and analyzing complex software, finding the source code line corresponding to a memory address can be a challenging task. This is where Linux addr2line tool comes in handy. Addr2line is a powerful command-line tool that helps in translating memory addresses to file names, line numbers, and function names. In this article, we will explore the features and usage of addr2line, along with some practical examples.
Usage and Syntax
Addr2line is usually used in conjunction with a debugger such as gdb (GNU Debugger). It takes as input an executable file and memory addresses and provides detailed information about those addresses. The basic syntax of addr2line is as follows:
<pre><code>addr2line [options] [-e executable] [addresses...]
</code></pre>
Here, the <code>-e</code> option is used to specify the executable file. The <code>addresses</code> parameter represents the memory addresses that you want to analyze.
Practical Examples
Let's dive into some practical examples to understand how addr2line works.
Example 1: Resolving function names
Suppose we have a binary file named <code>program</code> and we want to find the function name corresponding to a memory address <code>0x401234</code>. We can use the following command:
<pre><code>addr2line -e program 0x401234
</code></pre>
This will give us the name of the function associated with the memory address.
Example 2: Locating source code lines
In addition to function names, addr2line can also help us find the source code line corresponding to a memory address. Let's say we have an address <code>0x400abc</code> and we want to know the exact line number in the source code. We can use the following command:
<pre><code>addr2line -e program -f -C -i 0x400abc
</code></pre>
Here, the <code>-f</code> option displays the file name, while the <code>-C</code> option demangles C++ function names. The <code>-i</code> option displays the exact line number.
Example 3: Analyzing backtraces
Addr2line is particularly useful when analyzing backtraces obtained from a crash or error. Backtraces provide a list of memory addresses, and addr2line can help us identify the corresponding functions and source code lines.
Let's assume we have a backtrace that looks like this:
<pre><code>0x401234
0x400abc
0x403def
</code></pre>
We can use the following command to obtain the corresponding function names and source code lines:
<pre><code>addr2line -e program -f -C -i 0x401234 0x400abc 0x403def
</code></pre>
This will provide us with a detailed analysis of each memory address.
Conclusion
Linux addr2line is an invaluable tool when it comes to debugging and analyzing software. With its ability to translate memory addresses into function names and source code lines, addr2line helps developers pinpoint the exact location of issues. By leveraging addr2line in conjunction with a debugger, developers can save time and effort in troubleshooting and fixing bugs.
Remember to always keep addr2line in your debugging arsenal, as it can greatly simplify the process of understanding and resolving issues in your software.

linux addr2line

Linux addpart is a useful command that allows you to inform the kernel about the existence of a specific partition. By using this command, you can easily add a new partition to your Linux system. This article will guide you through the process of using addpart and provide you with a clear understanding of its functionality.
To use the addpart command, open your terminal and enter the following syntax:
<pre><code>sudo addpart [device] [partition number] [start sector] [end sector]
</code></pre>
Let's break down the command and understand each parameter:
<ul>
<li>sudo is used to run the command as the superuser, granting you the necessary permissions to make changes to the system.</li>
<li>addpart is the command itself, followed by the device name, which refers to the specific disk you want to add the partition to.</li>
<li>The partition number indicates the number you want to assign to the new partition.</li>
<li>The start sector and end sector define the boundaries of the partition within the disk.</li>
</ul>
For example, to add a new partition named &quot;sdb1&quot; to the disk &quot;sdb&quot; starting from sector 2048 and ending at sector 4096, you would use the following command:
<pre><code>sudo addpart /dev/sdb 1 2048 4096
</code></pre>
Once you execute the command, the kernel will be informed about the existence of the new partition. You can then proceed with formatting and mounting the partition to start using it.
It's important to note that adding a new partition may affect the existing data on the disk. Therefore, it's crucial to backup any important information before making any changes to your system.
In summary, the addpart command in Linux is a powerful tool that allows you to add a new partition to your system. By using this command, you can easily inform the kernel about the new partition's existence and continue using it for your storage needs.
So, go ahead and give the addpart command a try. It's a simple yet effective way to expand your disk space and improve the functionality of your Linux system.

linux addpart: Tell the kernel about the existence of the specified partition

<h3>Introduction</h3>
In the world of Linux, there are countless tools and commands that can help you manage and manipulate your system. One such command is &quot;addpart,&quot; which allows you to add partitions to your hard drive. This powerful tool offers a flexible way to customize your storage space, providing you with more control over your filesystem. In this article, we will delve into the functionality and usage of the &quot;addpart&quot; command, exploring how it can enhance your Linux experience.
<h2>Usage and Syntax</h2>
The &quot;addpart&quot; command is part of GNU parted, a popular disk partitioning tool used in Linux systems. It enables you to create new disk partitions without losing any existing data. This can be highly useful when you need to resize your storage capacity or organize your filesystem more efficiently.
To use the &quot;addpart&quot; command, open a terminal and type the following:
<pre><code>sudo parted /dev/sdX ---script --- mkpart primary [file system type] [start] [end]
</code></pre>
Here's what each component of the command signifies:
<ul>
<li><code>/dev/sdX</code>: Replace 'X' with the appropriate drive identifier. For instance, if you want to add a partition to &quot;sda,&quot; you would use <code>/dev/sda</code>.</li>
<li><code>--script</code>: This option allows for non-interactive operation, preventing any prompts.</li>
<li><code>mkpart primary</code>: This specifies that the new partition should be created as a primary partition.</li>
<li><code>[file system type]</code>: Specify the desired file system type for the new partition, such as ext4, xfs, or ntfs.</li>
<li><code>[start]</code> and <code>[end]</code>: Determine the start and endpoint of the partition, represented in bytes, kilobytes, megabytes, gigabytes, or terabytes.</li>
</ul>
Once you have entered the command, execute it, and the &quot;addpart&quot; command will create a new partition on the specified device according to your parameters.
<h2>Practical Example</h2>
Let's illustrate the usage of the &quot;addpart&quot; command with an example. Suppose we want to create a new partition on &quot;/dev/sdb&quot; with a file system type of ext4, starting at 1GB and ending at 2GB:
<pre><code>sudo parted /dev/sdb ---script --- mkpart primary ext4 1GB 2GB
</code></pre>
This command will promptly create a new partition on the &quot;/dev/sdb&quot; device with the specified file system type extending from 1GB to 2GB. Feel free to adjust the parameters to suit your requirements.
<h2>Conclusion</h2>
Operating systems like Linux provide a diverse set of tools to empower users to control and manage their systems effectively. The &quot;addpart&quot; command, a crucial component of GNU parted, is one such tool that allows for seamless partitioning of storage devices. By utilizing this command, you can effortlessly create new partitions and optimize your filesystem, enhancing the overall performance and functionality of your Linux system. So, go ahead, experiment, and unlock the full potential of your storage setup using the &quot;addpart&quot; command in Linux.

linux addpart

The <code>add-apt-repository</code> command in Linux is a powerful tool that enables us to easily add new software repositories to our system. But did you know that it can also be used to enable source packages? In this article, we will explore how to use <code>add-apt-repository</code> to enable source packages and why it is useful.
To enable source packages, we need to first ensure that the <code>software-properties-common</code> package is installed on our system. This package provides the necessary tools and libraries for managing software repositories. If it is not installed, we can easily install it by running the following command:
<pre><code class="language-bash">sudo apt-get update
sudo apt-get install software-properties-common
</code></pre>
Once the package is installed, we can use the <code>add-apt-repository</code> command with the <code>-s</code> or <code>--enable-source</code> option to enable source packages for a specific repository. For example, let's say we want to enable source packages for the official Ubuntu repositories. We can accomplish this by running the following command:
<pre><code class="language-bash">sudo add-apt-repository -s &quot;deb-src http://archive.ubuntu.com/ubuntu/ $(lsb_release -sc) main&quot;
</code></pre>
This command adds a new software repository with the <code>deb-src</code> prefix, indicating that it contains source packages. The <code>$(lsb_release -sc)</code> part is a command substitution that retrieves the codename of the currently installed Ubuntu release.
Once the repository is added, we need to update the package lists to include the newly added source packages. We can do this by running:
<pre><code class="language-bash">sudo apt-get update
</code></pre>
Now that the source packages are enabled, we can use the <code>apt-get source</code> command to download and extract the source code for a specific package. For example, if we want to obtain the source code for the <code>nginx</code> package, we can run:
<pre><code class="language-bash">sudo apt-get source nginx
</code></pre>
This command will download the source code for the <code>nginx</code> package and extract it to the current directory. We can then navigate to the extracted directory to view and modify the source code as needed.
Enabling source packages can be particularly useful for developers and advanced users who want to study or modify the source code of a specific package. It allows us to gain a deeper understanding of how the software works and customize it to suit our needs.
In conclusion, the <code>add-apt-repository</code> command in Linux not only allows us to easily add new software repositories but also enables us to enable source packages. By using the <code>-s</code> or <code>--enable-source</code> option, we can add repositories containing source packages and then use the <code>apt-get source</code> command to obtain and modify the source code. This functionality is especially valuable for developers and advanced users who want to explore and customize the software they use.

linux add-apt-repository: Enable source packages

Updating the Package Cache after Adding a Repository in Linux
When you add a new repository to your Linux system using the <code>add-apt-repository</code> command, it's essential to update the package cache. This ensures that your system recognizes the new repository and can retrieve the latest package information. Here's how you can easily accomplish this task.
To update the package cache, open a terminal window and enter the following command:
<pre><code class="language-bash">sudo apt update
</code></pre>
This command will refresh the package cache on your system, retrieving the latest information about available updates and new packages from all configured repositories. It's important to run this command after adding a new repository to ensure that any packages or updates from the added repository are included in subsequent package management operations.
Once you execute the command, you will see the package manager retrieving information from each enabled repository. This process may take a few moments, depending on the speed of your internet connection and the number of repositories configured.
After the update process is completed, the package manager will display the updated package information, informing you about the number of packages that can be upgraded or installed. You can then proceed with any package management operations, including installing, upgrading, or removing packages from your system.
In case you encounter any issues during the update process, such as failing to reach a repository or a connection error, you may need to double-check the repository URL or verify your internet connectivity. Additionally, it's always a good idea to ensure that the repository you have added is trustworthy and reliable, as faulty or malicious repositories can potentially compromise the security and stability of your system.
In conclusion, when you add a new repository to your Linux system using the <code>add-apt-repository</code> command, it's crucial to update the package cache afterward. This ensures that your system takes advantage of the latest package information from all configured repositories. By following the simple steps outlined above, you can easily update the package cache and keep your system up-to-date with the latest software packages and updates.
Remember to regularly perform this update process to stay informed about available software updates and security patches for your Linux distribution, thereby maintaining the stability and security of your system.

linux add-apt-repository: Update the package cache after adding a repository

How to Remove an Apt Repository in Linux Using the <code>add-apt-repository</code> Command
When using Linux, managing apt repositories is an essential part of the system administration. Apt repositories are used to provide software packages for installation and updates. However, at times you might want to remove an apt repository from your system. In this article, we will explore how to remove an apt repository using the <code>add-apt-repository</code> command.
To remove an apt repository, we will use the <code>add-apt-repository</code> command with the <code>--remove</code> option followed by the repository URL. Let's take a closer look at how to do this:
<pre><code class="language-shell">$ sudo add-apt-repository --remove &lt;repository URL&gt;
</code></pre>
For example, if you want to remove the repository with the URL <code>https://example.com/repository</code>, you would run the following command:
<pre><code class="language-shell">$ sudo add-apt-repository --remove https://example.com/repository
</code></pre>
Executing this command will remove the specified repository from your system. It is important to note that removing a repository does not uninstall any packages that were installed from that repository.
It is good practice to verify the removal by checking the repository list after executing the command. To do this, you can use the following command:
<pre><code class="language-shell">$ sudo apt update
</code></pre>
This command will update the package lists and remove the specified repository from the sources.
In case you need to remove multiple repositories, you can simply repeat the <code>add-apt-repository --remove</code> command for each repository URL.
Remember to use the <code>sudo</code> command to run the <code>add-apt-repository</code> command with administrative privileges. This ensures that you have the necessary permissions to modify the system's repository configuration.
Removing an unnecessary or deprecated repository can help ensure the security and stability of your Linux system. It also prevents potential conflicts between different repositories and their packages.
In conclusion, managing apt repositories is an important aspect of Linux system administration. Removing an apt repository using the <code>add-apt-repository</code> command is a straightforward process. By following the steps outlined in this article, you can easily remove an apt repository from your Linux system, keeping it clean and optimized.
Table: Summary of Commands
<table>
<thead>
<tr>
<th>Command</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>sudo add-apt-repository --remove &lt;repository URL&gt;</code></td>
<td>Removes the specified apt repository</td>
</tr>
<tr>
<td><code>sudo apt update</code></td>
<td>Updates the package lists and removes the repository from the sources</td>
</tr>
</tbody>
</table>
Remember to substitute <code>&lt;repository URL&gt;</code> with the actual URL of the repository you want to remove.
Now you have the knowledge to remove apt repositories in Linux using the <code>add-apt-repository</code> command. Always make sure to double-check the repository URLs before executing the removal command to avoid accidentally removing a necessary repository.

linux add-apt-repository: Remove an apt repository

Adding a new apt repository in Linux using the <code>add-apt-repository</code> command is a simple way to expand your software sources and access additional packages. This command is specifically designed for Debian-based distributions, such as Ubuntu.
To add a new apt repository, simply follow these steps:
<ol>
<li>
Open a terminal by pressing <code>Ctrl + Alt + T</code>.
</li>
<li>
Type the following command to install the necessary utility, if it is not already installed:
</li>
</ol>
<pre><code class="language-bash">sudo apt install software-properties-common
</code></pre>
<ol start="3">
<li>Once the installation is complete, you can use the <code>add-apt-repository</code> command to add a repository. The basic syntax is as follows:</li>
</ol>
<pre><code class="language-bash">sudo add-apt-repository repository_url
</code></pre>
Replace <code>repository_url</code> with the URL of the repository you wish to add.
Note: Some repositories may require additional steps, such as importing a GPG key. Please refer to the repository's documentation for specific instructions.
For example, if you wanted to add the popular Wine repository, you would use the following command:
<pre><code class="language-bash">sudo add-apt-repository 'deb https://dl.winehq.org/wine-builds/ubuntu/ focal main'
</code></pre>
After running the command, you will see output similar to the following:
<pre><code>Hit:1 http://archive.ubuntu.com/ubuntu focal InRelease
Get:2 http://archive.ubuntu.com/ubuntu focal-updates InRelease [114 kB]
...
Hit:12 https://dl.winehq.org/wine-builds/ubuntu focal InRelease
Reading package lists... Done
</code></pre>
Once the repository is added, you can proceed to update the package lists by executing the following command:
<pre><code class="language-bash">sudo apt update
</code></pre>
Tips:
<ul>
<li>Make sure you trust the repository you are adding, as it can potentially affect the stability and security of your system.</li>
<li>Always ensure you are using the correct repository URL for your Linux distribution version.</li>
<li>To remove a previously added repository, you can use the <code>remove-apt-repository</code> command. For example:</li>
</ul>
<pre><code class="language-bash">sudo remove-apt-repository repository_url
</code></pre>
That's it! You can now explore and install packages from the newly added apt repository using the <code>apt</code> or <code>apt-get</code> commands. Happy exploring!

linux add-apt-repository: Add a new apt repository

<h3>Introduction</h3>
In the world of Linux, package management is an essential aspect of keeping your system up-to-date and secure. One popular tool used for package management is <code>add-apt-repository</code>. This nifty command allows you to easily add new software repositories to your Ubuntu or Debian-based system, expanding your access to a wider range of applications and updates.
<h3>Adding a Repository</h3>
To add a new repository using <code>add-apt-repository</code>, you simply need to specify the repository's URL as an argument. Let's say you want to add the repository for a popular code editor called Visual Studio Code. Instead of manually editing files or adding entries, you can use the following command:
<pre><code class="language-bash">sudo add-apt-repository &quot;deb [arch=amd64] https://packages.microsoft.com/repos/vscode stable main&quot;
</code></pre>
This command adds the Visual Studio Code repository to your system. The <code>&quot;deb [arch=amd64] https://packages.microsoft.com/repos/vscode stable main&quot;</code> part describes the repository details, such as its architecture, URL, and distribution. Make sure to replace this portion with the actual repository information for the software you want to add.
<h3>Verifying the Repository</h3>
After adding a new repository, it is important to verify its authenticity and ensure that it is correctly added to your system. To do this, you'll need to import the repository's GPG key. This key is used to verify the integrity and authenticity of the packages provided by the repository.
Once you have the key's fingerprint or identifier, you can use the following command to import it:
<pre><code class="language-bash">sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys &lt;key_fingerprint&gt;
</code></pre>
Replace <code>&lt;key_fingerprint&gt;</code> with the actual fingerprint or key identifier for the repository you added. This step ensures that only trusted packages are installed on your system.
<h3>Updating and Installing Packages</h3>
Now that you have added a new repository, you can proceed to updating your package lists and installing software from the newly added repository. Run the following commands to perform these tasks:
<pre><code class="language-bash">sudo apt update
sudo apt install &lt;package_name&gt;
</code></pre>
Replace <code>&lt;package_name&gt;</code> with the name of the software you want to install from the repository. Running <code>apt update</code> updates your package lists, making sure you have the latest information about available packages. The <code>apt install</code> command installs the specified package, pulling it from the newly added repository if it is available.
<h3>Conclusion</h3>
Using <code>add-apt-repository</code> is a convenient way to expand your software sources on Ubuntu and Debian-based systems. It simplifies the process of adding repositories and allows you to easily install software from those repositories. Remember to verify the authenticity of the added repositories and keep your system up-to-date by regularly updating your package lists. With the power of <code>add-apt-repository</code>, you can enhance your Linux experience and access a wider range of applications and updates with ease.

linux add-apt-repository

Extracting Information from /proc in Linux ACPI
ACPI, which stands for Advanced Configuration and Power Interface, is an industry-standard protocol for power management in computers. In Linux, ACPI information is commonly accessed through a virtual file system located in the &quot;/sys&quot; directory. However, an alternative method exists to retrieve this information using the &quot;/proc&quot; directory. Let's explore how we can extract ACPI information from &quot;/proc&quot; in Linux.
To read ACPI information from &quot;/proc&quot;, we can use the &quot;procfs&quot; interface, which exposes kernel information in a hierarchical file structure. In this example, we'll retrieve the ACPI battery status.
First, we need to access the &quot;/proc/acpi/battery&quot; directory, where the battery information is stored. We can accomplish this by reading the contents of the directory using the &quot;readdir&quot; system call. Here is the code example:
<pre><code class="language-c">#include &lt;stdio.h&gt;
#include &lt;dirent.h&gt;

int main() {
 DIR *dir;
 struct dirent *entry;

 dir = opendir(&quot;/proc/acpi/battery&quot;);
 
 if (dir == NULL) {
 perror(&quot;Unable to open directory&quot;);
 return 1;
 }
 
 while ((entry = readdir(dir)) != NULL) {
 if (entry-&gt;d_type == DT_DIR) {
 printf(&quot;%s\n&quot;, entry-&gt;d_name);
 }
 }
 
 closedir(dir);
 
 return 0;
}
</code></pre>
With this code, we open the &quot;/proc/acpi/battery&quot; directory using the <code>opendir</code> function. Then, we read the directory's content using the <code>readdir</code> function. If an entry is a directory, we print its name. Finally, we close the directory using the <code>closedir</code> function.
Using the &quot;/proc&quot; directory to extract ACPI information provides an alternative approach to accessing kernel data. It can be particularly useful if the &quot;/sys&quot; directory is not available or accessible for some reason.
Please note that the code example provided is a basic illustration of accessing the &quot;/proc/acpi/battery&quot; directory. Depending on the specific ACPI information you want to extract, you may need to read and parse different files within the &quot;/proc&quot; hierarchy.
Remember to always consult the official documentation and resources for a deeper understanding of the ACPI implementation in Linux and its associated file structures.
Happy coding!

linux acpi: Extract information from /proc instead of /sys

Linux ACPI is a powerful tool that allows users to access and monitor various hardware information on their systems. By leveraging the ACPI (Advanced Configuration and Power Interface) framework, Linux can gather data such as battery status, temperature, and fan speeds. In this article, we will dive into how to show all available information using Linux ACPI.
To retrieve ACPI information, we can use the <code>acpi</code> command-line utility. This command provides a straightforward way to get detailed hardware information directly from the kernel. Let's take a look at an example:
<pre><code class="language-bash">acpi -V
</code></pre>
This command will display a comprehensive list of information, including battery status, thermal zone readings, and power adapter details. The output will vary depending on your system and the available ACPI data.
To view battery information specifically, we can use the following command:
<pre><code class="language-bash">acpi -b
</code></pre>
This will show details such as the battery's capacity, remaining charge, and current status (charging, discharging, or fully charged). It's essential to keep an eye on battery health, especially for laptop users who rely heavily on their devices.
Temperature monitoring is also a crucial aspect of system maintenance. To check the thermal zone temperatures, you can run the following command:
<pre><code class="language-bash">acpi -t
</code></pre>
This will give you the current temperature readings for each available thermal zone. Monitoring these temperatures can help identify potential issues with cooling or excessive heat.
Additionally, if you want to examine the status of your power adapter, the following command will provide detailed information:
<pre><code class="language-bash">acpi -a
</code></pre>
This command will tell you if your system is connected to an AC power source or running on battery.
By utilizing the Linux ACPI framework and the <code>acpi</code> command-line utility, you can efficiently retrieve vital hardware information on your system. Whether you need to monitor battery health, keep an eye on temperature levels, or check power source details, Linux ACPI has got you covered.
Remember to consult your system's documentation or online resources for additional options and flags that can further enhance the functionality of the <code>acpi</code> command.