LINUX Commands

Troubleshooting is crucial for DevOps engineers managing Linux environments!

Here’s an expanded list of commonly used troubleshooting commands with more examples:

1. dmesg: Kernel messages for hardware and system errors.

• Example: dmesg | grep -i error

1. top/htop: Real-time system resource monitoring.

• Example: htop

1. free: Memory usage overview.

 — Example: free -m

1. df: Disk space usage analysis.

• Example: df -hT

1. netstat: Network connections and routing tables.

• Example: netstat -tuln, netstat -s

1. ping: Testing network connectivity.

 — Example: ping -c 4 google.com

1. traceroute/mtr: Tracing network routes and latency.

• Example: mtr google.com

1. ifconfig/ip: Network interface configuration.

• Example: ip addr show, ifconfig -a

1. journalctl: Viewing system logs.

 — Example: journalctl -u sshd.service

1. lsof: Checking open files and associated processes.

• Example: lsof -i :port\_number

1. ps: Process status and information.

 — Example: ```ps

• Ef | grep process_name```

1. systemctl: Managing systemd services.

• Example: systemctl start/restart/stop service\_name

13.grep: Searches for patterns in files.

— Example: grep "pattern" file.txt, grep -r "pattern" directory/

Here are some Linux commands that are commonly used on a daily basis along with examples:

1. ls: Lists files and directories in the current directory.

• Example: ls, ls -l, ls -a

1. cd: Changes the current directory.

 — Example: cd Documents, cd .. (moves up one directory)

1. pwd: Prints the current working directory.

• Example: pwd

1. mkdir: Creates a new directory.

• Example: mkdir new\_folder

1. rm: Removes files or directories.

• Example: rm file.txt, rm -r directory

1. cp: Copies files or directories.

• Example: cp file.txt new\_location/

1. mv: Moves or renames files or directories.

 — Example: mv file.txt new\_location/, mv old\_name.txt new\_name.txt

1. touch: Creates a new empty file.

• Example: touch new\_file.txt

1. grep: Searches for patterns in files.

 — Example: grep “pattern” file.txt, grep -r “pattern” directory/

1. cat: Displays the contents of a file.

• Example: cat file.txt

1. nano or vim: Text editors for creating and editing files.

• Example: nano file.txt, vim file.txt

1. chmod: Changes file permissions.

 — Example: chmod +x script.sh (gives execute permission to a script)

1. sudo: Executes a command with superuser privileges.

• Example: sudo apt update, sudo rm protected\_file

1. apt or yum: Package managers for installing, updating, and removing software packages.

 — Example: sudo apt install package\_name, sudo yum install package\_name

1. find: Searches for files in a directory hierarchy.

 — Example: find . -name “\*.txt”

Some other commands along with examples:

1. clear: Clears the terminal screen.

• Example: clear

1. man: Displays the manual pages for a command.

• Example: man ls (displays the manual for the ls command)

1. history: Displays the command history of the current session.

• Example: history

1. date: Prints the current date and time.

 — Example: date

1. sleep: Delays execution for a specified amount of time.

• Example: sleep 5 (pauses for 5 seconds)

1. uptime: Displays system uptime and load average.

• Example: uptime

1. whoami: Prints the current username.

 — Example: whoami

1. id: Displays user and group information for the current user or specified user.

• Example: id

1. groups: Lists the groups the current user belongs to.

 — Example: groups

1. passwd: Allows users to change their passwords.

• Example: passwd

1. who: Shows who is logged on.

 — Example: who

1. last: Displays a list of last logged in users.

• Example: last

1. kill: Sends a signal to terminate a process.

• Example: kill PID (where PID is the process ID)

1. cat: Concatenates and displays the content of files.

• Example: cat file.txt

1. more: Displays the content of a file one page at a time.

• Example: more file.txt

1. rm: Removes files or directories.

 — Example: rm file.txt

1. ln: Creates links between files.

• Example: ln -s /path/to/file /path/to/link

1. hostname: Prints or sets the system’s hostname.

• Example: hostname, hostname new\_host\_name

These commands are fundamental for managing and interacting with a Linux system. Experiment with them to get familiar with their functionalities!