> For the complete documentation index, see [llms.txt](https://chunhthanhde.gitbook.io/google-learning-programs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://chunhthanhde.gitbook.io/google-learning-programs/google-it-support-professional-certificate/course-3-operating-systems-and-becoming-a-power-user/module-6-operating-systems-in-practice/3.logging/3.linux-logs.md).

# Linux Logs

## 📁 **Log Storage Location**

* **Directory:** Logs in Linux are stored in the `/var/log` directory. The `/var` directory stands for "variable," indicating it contains files that frequently change. Since logs are continuously updated, they are kept here. 📂

## 🔍 **Common Log Files**

* **`/var/log/auth.log`:** Logs authorization and security-related events. 🔒
* **`/var/log/kern.log`:** Contains kernel messages. 🛠️
* **`/var/log/dmesg`:** Stores system startup messages. Useful for troubleshooting boot-up issues. 🚀
* **`/var/log/syslog`:** A comprehensive log file that captures almost all system events except some off events. This file is typically the first place to check for detailed system information. 📜

## 🗂️ **Log Management**

* **Log Rotation:** To manage disk space, Linux uses a process called log rotation, handled by the `logrotate` utility. This process ensures older log files are archived or deleted to make room for new logs. 🔄
* **Customizing Log Rotation:** You can adjust settings to keep logs for a longer period if needed for troubleshooting. 🗓️

## 🌐 **Centralized Logging**

* **Purpose:** For managing multiple systems, centralized logging allows you to aggregate logs from various machines into a single location for easier analysis. 🌍

## 📊 **Understanding Log Entries**

* **Timestamps:** Logs often use Unix or epoch time, representing the number of seconds since midnight on January 1, 1970. This format might look like a long string of numbers, but it is standard for Unix-based systems. 🕰️

## 🔍 **Reading Logs**

* **Example:** When examining logs, you might encounter a complex format. The next lesson will cover troubleshooting using logs, including parsing and interpreting log entries. 📚