All About Linux.

Linux password rules can be stored in different places, depending on whether they check a new password or control when an account password expires. A Linux password policy combines password-quality checks with account settings that determine when passwords expire. I’ll show how to inspect the active PAM password stack and read an account’s aging settings

Working with text records at the shell can mean finding the rows and fields that matter. awk reads text records and lets you select fields or calculate totals. I’ll show how to select fields and summarize matching records, then save the program in an awk file for reuse. TL;DR: Use awk to select and reshape

To see which login sessions a Linux system has recorded, use the who command. It reads login records, usually from utmp, and lists the sessions they contain. I’ll explain its output fields and show how to select the session associated with standard input. TL;DR The who command lists login sessions recorded on a Linux system,

When a file or directory needs different access, the task is to change its permissions without opening it up more than intended. chmod changes the rules that control access to files and directories. I’ll show how to set permissions with a number such as 640 or a letter-based change such as u+x, then check the

Terminal output can be useful to review alongside the commands that produced it. The Linux script command records an interactive terminal session in a file called a typescript, which contains entered commands and visible results. I’ll show you how to record and replay a session, and how to check its log for private input. TL;DR:

To schedule a Linux command for one future run, use at. The at utility queues a shell command as a job for the atd scheduler service to run once at a later time. I’ll explain what at does and show how to schedule a one-time job. TL;DR: Schedule a one-time Linux command The at command

A command can finish without showing how long it took. The Linux time command reports a command’s elapsed duration and CPU time. I’ll show how to time a command and choose the right time implementation for its summary. TL;DR: Time a Linux Command Prefix a command with time to measure it, and use /usr/bin/time when

A Linux machine may need to reach a service on another host, and a port check can show whether a TCP connection gets through. The telnet command attempts that connection and lets you interact with the endpoint. I’ll explain how to run the check and how to interpret its response. TL;DR The telnet command opens