𝗖𝗘 - 𝗖𝘆𝗯𝗲𝗿 𝗘𝘅𝗽𝗲𝗿𝘁

#meme happens every time

📚 A Quick Guide to Bash Special Variables: • $1, $2, $3, ... These are the positional parameters, representing arguments passed to the script or function. $1 is the first argument, $2 is the second, and so on. • "$@" An array-like construct containing all positional parameters. Each parameter is treated as a separate quoted string, preserving spaces. • "$*" Expands all positional parameters as a single string, separated by the current Internal Field Separator (IFS). • $# The number of positional parameters passed to the script or function. • $- Displays the current shell options as a string (e.g., himBH for interactive, monitor mode, etc.). • $$ The process ID (PID) of the current shell instance, not any subshell it may invoke. • $_ Holds the last argument of the previous command or the absolute path of the shell script executed at startup. • $IFS The Internal Field Separator, used to split input into fields during expansion. Defaults to spaces, tabs, and newlines. • $? The exit status of the last executed command. A value of 0 typically means success, while non-zero indicates an error. • $! The PID of the most recently executed background command. • $0 The name of the script or shell being executed, including its path if run with one.

🛜 Types of IPv6 Addresses

📚 Docker components explained

🐧 Quick Linux tip:

When you need to create several directories at once, you don’t have to do it one by one.

The mkdir command supports brace expansion, letting you create multiple nested directories in a single go.

$ mkdir -p ~/scripts/{site-01,site-02}/{backup,monitoring,network}

This instantly creates folders for two sites, each with its own backup, monitoring, and network directories. A neat way to save time and keep your directory structure organized.

This hierarchy map is your cheat sheet to the Linux filesystem.

📚  SPF Protocol Explained: ~ @TheCodingExpert

🌐 Git Commands Cheat Sheet

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🔰 Quick Linux Tip🐧 You can enable timestamps in your bash command history to see when you ran previous commands. This can be useful for tracing what you were working on and when. To add timestamps to your history, just set the HISTTIMEFORMAT environment variable like so: $ export HISTTIMEFORMAT="%F %T " Now when you view your history or grep through it, you'll see a timestamp next to each command indicating when it was run: $ history | tail -n 5 Or to save a couple of keystrokes: $ history 5 The format "%F %T" shows the date and time, but you can customize it to your liking. Note: This does not put historical timestamps on commands you executed before setting HISTTIMEFORMAT and also this only works in bash.

📚 Loops in bash scripting

🔰 Understanding Linux System Logs

System logs, often found in /var/log directory in Linux systems, are essential for monitoring and troubleshooting system issues. Here are short notes on some common system logs:

syslog: A general-purpose system log file that contains messages from various system services and applications. It's the main log file that many other logs feed into. auth.log: Records authentication-related messages, including successful and failed login attempts, password changes, and user authentication events. kern.log: Logs kernel-related messages, such as hardware errors, kernel module loading, and other kernel activities. messages: A catch-all log file that records various system messages, including system startups, shutdowns, and general system-related events. dmesg: Displays kernel ring buffer messages, providing a real-time view of kernel-related events and hardware detection during system boot-up. cron: Logs messages related to cron jobs and scheduled tasks, including when they run, and any errors encountered during execution. secure: Records security-related messages, including authentication attempts, privilege escalation, and other security-related events. apache/access.log and apache/error.log: These logs are specific to the Apache web server. access.log records HTTP access logs, while error.log logs Apache server errors and warnings. nginx/access.log and nginx/error.log: Similar to Apache logs, these logs are specific to the Nginx web server and record access and error events. mysql/error.log: Records errors and warnings encountered by the MySQL database server, including startup errors, query failures, and database crashes.

These logs provide valuable insights into system performance, security events, and troubleshooting information. Regularly monitoring and analyzing these logs can help maintain system health and identify potential issues before they escalate