Introduction to Linux Operating System Basics

Common Linux Commands

cd change directory (change directory)
pwd display current working directory (print working directory)
help help

ls display list of files and directories (list)
mkdir create directory (make directory)
cp copy files or directories (copy)

Internal commands: help + command (help cd)
External commands: man + command (man ls)

pwd display current working directory (print working directory)
touch create empty file                            
mkdir create directory (make directory) -p create parent directory if it does not exist (parents)            
cp copy files or directories (copy) -r recursively copy files and subdirectories under the specified directory (recursive)     
mv move files or directories, rename files or directories (move)

rm delete files (remove) -r delete all files in the directory (recursive) -f force delete files or directories (force)
rmdir delete empty directories (remove directory)
cat display text file content (catenate)
more, less paginate display text file content
head, tail view the beginning or end of the text
head -n  5  a.log view the first 5 lines of a.log
tail  -F b.log follow the log file

wc count lines, words, characters in text (word count)
-m count characters in text
-w count words in text
-l count lines in text
find search for specified files in the file system
find /etc/ -name "aaa"
grep search for specified strings in specified text files
ln create link files (link) -s create symbolic links to source files instead of hard links (symbolic)

top display the processes consuming the most resources in the current system
ps display the instantaneous status of processes -e /-A display all processes, environment variables -f full format -a display all processes for all users (including other users) -u display processes in order of username and start time -x display processes without controlling terminal
kill kill a process
kill -9 pid
df display disk space usage of file systems

du display the total disk space used by specified files (directories)
-h display file sizes in K, M, G (human-readable)
-s only display the total size of each file (summarize)
free display current memory and swap space usage
netstat display network status information -a display all connections and listening ports -t (tcp) only display tcp-related options -u (udp) only display udp-related options -n refuse to display aliases, display all conversions to numbers.
-p display the name of the program that establishes the relevant link
ifconfig detailed network configuration of network card
ping test network connectivity

gzip compress (decompress) files or directories, compressed file suffix is gz
bzip2 compress (decompress) files or directories, compressed file suffix is bz2
tar package (unpackage) files and directories

Command format: gzip [options] file name to compress (decompress)
-d decompress the compressed file
-l display the size of the compressed file, the size of the uncompressed file, and the compression ratio (list)
-v display file name and compression ratio (verbose)
-num adjust the speed of compression with specified number num, -1 or --fast indicates the fastest compression method (low compression ratio), -9 or --best indicates the slowest compression method (high compression ratio). The system default is 6

Command format: bzip2 [-cdz] document name -c output the data generated during the compression process to the screen
-d decompress parameter (decompress)
-z compression parameter (compress)
-num adjust the speed of compression with specified number num, -1 or --fast indicates the fastest compression method (low compression ratio), -9 or --best indicates the slowest compression method (high compression ratio). The system default is 6

-c create a compressed file parameter instruction (create)
-x extract a compressed file parameter instruction (extract)
-z whether to use gzip for compression
-j whether to use bzip2 for compression
-v display files during compression (verbose)
-f use file name, immediately after f should be the file name (file)

shutdown system shutdown
-r immediately reboot after shutdown
-h shut down without restarting
halt shut down and power off
shutdown -h reboot restart
shutdown -r

• Be good at checking man pages (manual) and other help documents

• Utilize the Tab key well

• Master some shortcut keys

ctrl + c (stop current process)
ctrl + r (view command history)

ctrl + l (clear screen, same effect as clear command)