pidof firefox
ps aux | grep -i firefox
pgrep firefox

pgrep firefox


$ date

$ timedatectl set-timezone Asia/Shanghai

$ uname -r

shopt -s extglob
$ rm -v !(“filename”)
enable the extglob shell option , remove everything except a filename

cat /etc/os-release

yum install epel-release
CentOS7’s depending pip repositories
yum -y install python-pip
install python pip

$ jq . config.json


find / -name ‘filename’ or find -name ‘filename’


find / -name ‘path’ -type d


find . | xargs grep -ri ‘content’
//find . | xargs grep -ril ‘content’ 只显示文件名称

pwd: print current dir
ls -l: show details
ls -a: show hidden
ls -la: both hidden and details
clear: clear terminal
cd: just type cd to home directory
cd: change dir
cd..: go up once
cd ../..: go up twice
cd /: to the ver top


mkdir dirname: make dir
rmdir dirname: remove an empty dir

rm -rf dirname: remove an non-empty dir

touch filename: create file
rm filename: remove file
cp oldfilename newfilename: copy a file
mv oldfilename newfilename: rename a file
mv file dir: move a file to dir
cat file: read the file
grep content file: global regular expression print(search content in file)

name=ryan: store a variable called name as ryan
echo hello: print hello
echo $name: echo out the variable

cd bin dir
bash to run pycharm on linux

info commandName: print out the help document of a command
ctrl+ c: back to home

ls > filename: to copy all the ls result to a file(overwritten)
ls >> filename: to append all the result to a file (not over written)

-rw: means file
drw: means dir
rwx: means read, write, execute
-rwxrw-r-x: means a file, owner can rwx it, group can read write it, the rest of users can read and execute it
u – user
g – group
o – others

ryan ryan: first is the owner of the file, second is the group it belong to
sudo useradd Bucky: to add a new user named Bucky
sudo passwd Bucky: change passwd for Bucky
sudo groupadd hacker: add a group called hacker
sudo usermod -a -G hacker Bucky: append Bucky to hacker group(not removing the group it belongs before)
sudo usermod -a -g hacker Bucky: append Bucky to hacker group(removing the group it belongs before)
sudo userdel Bucky: delete Bucky user

chmod o+w filename: to change the permission while others can write
chmod 754 filename: to change a file to -rwx r-x –r
7, 5, 4 represents user, group, others
4 – read
2 – write
1 – execute
0 – no permissions
chmod 777 filename: all permissions to all people

sha1sum file: to get the hash number of the file

compress and decompress:

gzip Grocery\ List: when there is a space in filename, need to backslash
gzip filename: to zip a file to filename.gz
gunzip story: to unzip a file

tar cvf target.tar fileA fileB:
make a target.tar to include fileA and fileB
cvf – create, visualize, file
xvf – extract, visualize, file

apt: avanced package tool
sudo: super user do

sudo apt-get update
sudo apt-get install python3

java -version: print the version of java

SSH: Secure Shell
Set up ssh private and public keys:
in the local machines:
ssh-keygen -t rsa: create a private key, saved in /home/user/.ssh/
ssh-copy-id root@server’s IP: to add copy of private key to the server
ssh root@server’s IP: to connect to the server, and automatically add
in the server:
nano /etc/ssh/sshd_config
find #Authentication:
PermitRootLogin without-password
reload ssh: to restart the ssh service, when configuration is made

Transfer files using SFTP
sftp root@server’s IP
cd TargetDir
put Desktop/file: put the local file into the server via sftp
put -r Desktop/dir: to put a dir recursively (file in it included) to the working directory
get file Desktop/File: get the file from the server to the local machine and rename it as ‘File’
get -r dir Desktop/Dir: get the dir recursively from the server to the desktop and rename it as ‘Dir’
exit: to quit from ssh or sftp

sudo apt-get install gparted: to install an visualized app for partitioning
sudo gparted

Command Shell:
adding to the header of a script, and make Linux run the following command
chmod +rx file: to change the permission of a file to readable and executable
bash script: to run the script

ps: to list the processes that we owned and controlled manually
ps -ax: list all the processes in the background including the system processes
ProcessID Terminal 00:00:00(time of cpu comsummed) Name of command

without finishing the process, no control of the terminal, eg. xlogo
ctrl + c: interrupt the process in the foreground
cmd &: to run the cmd in the background
[1] 2710: JobNumber, PID
jobs: to list the current jobs(a special type of process)
fg %1: to turn the background job to the foreground
bg %1: to turn the background job to the foreground
ctrl + z: to pause the current foreground job
kill PID: to kill the process
kill JobNumber: to kill the job
kill -STOP cmd: to freeze the process
kill -CONT cmd: to unfreeze the process


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