Basics of Linux Operating System for Beginners

For example: ls  -la  /usr
ls: displays the list of files and directories (list)

-l    (long)-a  (all)         Note hidden files, special directories . and ..   -t    (time)

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

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

Internal command: help + command (help cd)
External command: 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 under the directory (recursive) -f force delete files or directories (force)
rmdir delete empty directories (remove directory)
cat display text file contents (catenate)
more, less paginate text file contents
head, tail view the beginning or end of text in a file
head -n  5  a.log view the first 5 lines of a.log
tail  -F b.log follow (loop read)

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 instantaneous process status -e /-A display all processes, environment variables -f full format -a display all users' processes (including other users) -u display processes in order of username and start time -x display processes without a control terminal
kill kill a process
kill -9 pid
df display file system disk space usage

du display total disk space used by specified files (directories) -h display file size 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) display only tcp-related options -u (udp) display only udp-related options -n refuse to display aliases, convert everything that can be displayed as numbers into numbers. -p display the program name that established the relevant link
ifconfig detailed network card configuration
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, directories

Command format: gzip [options] file name to compress (decompress) -d decompress the compressed file (decompress) -l display the size of the compressed file, the size of the uncompressed file, compression ratio (list) -v display file name and compression ratio (verbose) -num use specified number num to adjust compression speed, -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 use specified number num to adjust compression speed, -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 compression
-j whether to use bzip2 compression
-v display files during compression (verbose)
-f use file name, the file name must immediately follow f (file)

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

ctrl + c (stop current process)
ctrl + r (view command history)
ctrl + l (clear screen, same effect as the clear command)