• getent:

  • getent is a command-line utility used to retrieve entries from Name Service Switch (NSS) libraries, including information from databases such as /etc/passwd, /etc/group, /etc/hosts, and others.

  • It can be used to query various databases configured on the system, including passwd, group, hosts, services, protocols, and networks.

  • For example, getent passwd will display a list of all user accounts configured on the system.

• id:

  • id is a command-line utility that displays information about the current user or specified user, including user ID (UID), group ID (GID), and supplementary groups.

  • When run without arguments, it displays information about the current user. With a username as an argument, it displays information about the specified user.

• vmstat:

  • vmstat is a command-line utility used to display virtual memory statistics, including information about processes, memory, paging, block I/O, and CPU activity.

  • When you run vmstat, it displays a summary of system-wide memory usage, virtual memory statistics, and CPU utilization.

  • vmstat can be used to monitor system performance and identify potential bottlenecks.

• isof:

  • It seems like there might be a typo here. It's possible you meant ls -l which is used to list files and directories with detailed information such as permissions, owner, group, size, and modification time.

• alias:

  • alias is a command used to create shortcuts (aliases) for longer commands or command sequences. These aliases can be customized by users to simplify frequently used commands or to add options to existing commands.

• regex:

  • Regular expressions (regex) are not commands themselves but rather patterns used for matching strings within text. However, many commands support regex for pattern matching, such as grep, sed, and awk. Regex allows for powerful and flexible text searching and manipulation.

• nslookup:

  • nslookup is a command-line utility used to query DNS (Domain Name System) servers to obtain domain name or IP address information.

  • It's commonly used to perform DNS lookups, troubleshoot DNS-related issues, and verify DNS configurations.

• sed:

  • sed, short for stream editor, is a command-line utility used for text manipulation and transformation.

  • It operates by performing operations (such as search and replace) on input text streams according to specified commands or scripts.

• cut:

  • cut is a command-line utility used to extract sections from each line of input files.

  • It's commonly used to extract specific columns or fields from text files, using delimiter characters to specify the sections to extract.

• ps aux:

  • ps aux is a command used to display information about all running processes on the system.

  • It provides a detailed list of processes, including their process ID (PID), CPU and memory usage, user ownership, and command-line arguments.

  • The aux flags specify that it should display information about all processes (a) and provide additional details (u) such as user and memory usage.

• top:

  • top is a command-line utility that provides a dynamic, real-time view of system resource usage. It displays information about CPU, memory, processes, and more.

  • When you run top, it presents a continuously updated list of processes, sorted by various criteria such as CPU usage, memory usage, or runtime.

  • top also provides summary information about system-wide resource usage, including total CPU and memory utilization, number of processes, uptime, etc.

  • You can interact with top to sort processes, kill processes, change the display format, and more. Pressing keys like q quits top, k kills a process, r renice a process, etc.

• free:

  • free is a command-line utility used to display information about system memory usage, both physical and swap memory.

  • When you run free, it provides output showing total memory, used memory, free memory, shared memory, buffers, and cached memory.

  • The output of free also includes information about swap space, showing total swap, used swap, and free swap.

  • By default, free displays memory sizes in kilobytes. You can use the -h option to display sizes in a more human-readable format (e.g., megabytes, gigabytes).

In summary, top provides a dynamic view of system processes and resource usage, while free specifically focuses on displaying memory usage statistics. Both commands are valuable tools for monito

These commands are foundational utilities in Linux/Unix systems and are commonly used for system administration, troubleshooting, and text manipulation tasks.