RHCSA Essential Command-Line Tools Flashcards

Which command extracts a tarball named 'backup.tar.gz' into the current directory?

Answer: tar -xzf backup.tar.gz

tar -xzf extracts (-x) a gzip-compressed (-z) archive from the specified file (-f).

What does 'ps aux' show?

Answer: All running processes for all users with detailed info

ps aux uses BSD-style flags to show all processes (a), user-oriented format (u), and processes not attached to a terminal (x).

Which command sends signal 9 (SIGKILL) to a process with PID 1234?

Answer: kill -9 1234

kill -9 PID sends the SIGKILL signal which immediately terminates the process without cleanup.

What does the 'df -h' command display?

Answer: Disk space usage of mounted filesystems in human-readable form

df reports filesystem disk space usage, and -h formats sizes with KB/MB/GB units for readability.

Which command shows disk usage of the current directory and its subdirectories?

Answer: du -sh *

du -sh * shows the summarized (-s) human-readable (-h) disk usage of each item in the current directory.

How do you redirect both stdout and stderr to a file named 'output.log'?

Answer: command > output.log 2>&1

> output.log redirects stdout to the file, and 2>&1 redirects stderr (fd 2) to the same destination as stdout (fd 1).

What does 'history | grep ssh' display?

Answer: Previously run commands that contain 'ssh'

history outputs the command history list, and piping it to grep filters lines containing the string 'ssh'.