free -h

grep SwapTotal /proc/meminfo

df-h

cat /proc/meminfo | grep MemTotal

cat /proc/cpuinfo | grep "processor" |sort |uniq | wc -l

top

-i: Do not display any idle or zombie trips

View Java processes

View process details

View current process

View the specified port number

kill -9 process

nohup

ps ef | grep defunct

sudo netstat -tunlp | grep 44444

Internet Firewall

nc(natcat)

Check disk IO usage

tzselect

date

crontab

reboot

vi /etc/hostname

cat /proc/version

runlevel

uname -uname -m

vim /etc/redhat-release

Main categories of daemon processes

Correspondence between services and ports: /etc/services

Startup script and startup method of daemon process

Observe the services started by the system: netstat

How to start the service immediately after configuring startup

useradd

-c

-d

-g

-u

Command: passwd user

Example: passwd muye

cat /etc/passwd

userdel <options>

-r

Modify user-related attributes, such as user number, home directory, user group, login shell, etc.

-c

-d

-g

-G

-s

-u

-o

passwd -l

passwd -u

passwd -d

passwd -f

su/sudo-auth

groupadd

groupdel

cat /etc/group

tee

View the last 100 lines

Monitor the last 100 lines

View more and less in pages (less supports page turning forward)

View hidden files

Font color represents meaning

local copy

Transfer all files in the /root/lk directory on server A to the /home/lk/cpfile directory on server B.

Delete specified content files in batches

Delete files in a folder

mv mysql-5.6.33-linux-glibc2.5-x86_64 mysql

zip

tar

unzip

tar

cat /dev/null > file_name

Switch absolute directory

Switch relative directories

cp -r dir1 dir2

Create a directory

Create multi-level directories

pwd

Delete a single directory

Delete multi-level directories

du -h | sort -nr |head -20

which

whereis (find specific files)

locate

find

chown account name file or directory

chgrp -R account name file or directory

chown -R owner username.group name folder name

chmod wx filename

Definition of program and process

Child process and parent process

fork and exec: process call process

System or network service: a memory-resident process

multi-user environment

multitasking behavior

Seven basic terminal windows for a multi-login environment

Special process management behavior

Work management in bash environment: using & symbol

Consideration of system resource allocation issues for multi-users and multi-tasks

Directly throw the command to the background for "execution" &

Put the current work into the background and "pause": [ctrl]-z

View the current background job status: jobs

Bring background work to the front desk for processing: fg

Change the status of a job in the background to running: bg

Manage work in the background: kill

nohup command

PS

top: dynamically view process changes

pstree: process affinity

kill

killall

Priority(PRI) and Nice(NI) values

free: observe memory

uname: View system and core related information

uptime: View system startup time and workload

netstat: Track the network

dmesg: Analyze messages generated by the kernel

vmstat: detect system resource changes

fuser: Find the program that is using the file through the file (or file system)

lsof: List the file names opened by the process

pidof: Find out the PID of an executing process

rpm -qa | grep vnc(filename)

rpm -ivh vsftpd-3.0.2-22.el7.x86_64.rpm

ll /etc/yum.repos.d/

yum list

yum clean all

yum update

shift 4

shift 6(0)

gg

shift g

0

shift 4

After opening with vi: / keyword

Open unused file: cat filename | grep keyword

^ ,&

Variable definitions

Display and setting of variables

The function of environment variables

Language variables that affect the display results (locale)

Valid range of variables: export

Variable keyboard reading, array and definition

Limitations between file systems and programs: ulimit

Deletion, substitution and replacement of variable contents

Command alias configuration

Path and command search order

history: history command

Bash entry and welcome information:/etc/issue,/etc/motd

bash environment configuration file

Terminal environment configuration: stty, set

Wildcards and special symbols

Output type

/dev/null trash can black hole settings and special writing methods

tee: bidirectional redirection

Judgment basis for command execution

intercept command

Sorting and Statistics Instructions

Character conversion command

Parameter substitution

Effect of encoding on regular expressions

Advanced applications of grep

Basic regular expression characters

sed tool

Formatted printing: printf

Useful data processing tool: awk

-foreground

fdisk

mkfs

mke2fs

fsck

Mount command: mount

Uninstall command: unmount

Importance of login documents

Common file names

Related services and procedures required for login files

General format of login file content

Syslog configuration file: /etc/syslog.conf

Login file security configuration

Login file server configuration

logwatch provided by default in CentOS

Login file analysis tool written by Brother Niao himself

startx

sudo init 3

sudo init 5