How to expand a logical volume (LVM) in Linux

The Redis6 cluster must be created with redis-cli--cluster. It requires a minimum of 3 masters and 3 slaves, a total of 6 nodes. The client port and the corresponding cluster bus port (10000) must be opened. Correct configuration but blocked ports is a common cause of failure.

The most common and reliable way to import SQL files into MySQL is the command line tool mysql, which supports cross-platform, high efficiency and stability, and is suitable for files of all sizes. It can also be executed in the client through the source command, or using graphical tools such as phpMyAdmin and MySQL Workbench.

Linux systems need to use third-party tools for security scanning; lynis is suitable for lightweight local auditing, openvas must be deployed with Docker, nmap and nessus cannot be automatically connected, and the effectiveness of scanning depends on credentials, settings and feed updates.

The most reliable way is to use the iplinkshow command, because it is compatible with old and new kernels, has clear output, and does not confuse virtual interfaces; the MAC address is located after the link/ether line and can be accurately extracted with grep.

Slow query optimization requires four layers of troubleshooting: "Log → Execution Plan → System Indicators → Configure Hardware": first open slow_query_log to capture queries that exceed 1 second; then use EXPLAIN to analyze type, key, rows and Extra; then check sar, buffer pool hit rate, lock wait and number of connections; finally examine innodb_flush_method, redolog size, large field storage and network architecture.

uname-r is the most accurate and quick way to obtain the current kernel version number. It only outputs the release field such as 6.1.0-22-amd64, without redundant information, which is convenient for script parsing; other commands such as uname-v, uname-a or /proc/version have their own uses but are not specifically used for version extraction.

Using sudoaptinstallbuild-essential is the fastest under Ubuntu/Debian. It automatically installs gcc, g, make, libc6-dev, etc.; only installing gcc will report an error that stdio.h does not exist due to a missing header file.

When ZAP (ZedAttackProxy) is installed, it prompts "Java 64-bit file not found." The root cause is not that Java is not installed, but that the JRE that only contains the running environment is mistakenly installed; ZAP actually relies on JDK11 (such as JDK21) because it requires the use of development components such as compilers and debugging tools.