## Introduction
When we try the linux system, we need to delete a file, we can try the `rm` command to delete it quickly

This tutorial will teach you How to delete files in linux

## Command Line
Delete the `test.txt` file

```bash
rm -i test.txt
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| rm   |Remove (unlink) the FILE(s).|
| -i   |prompt before every removal.|

###  operation result
```
rm: remove regular empty file 'test.txt'? 
```

### Important reminder
It is recommended to try -i to delete files to prevent direct deletion of files

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


When we try the linux system, we need to delete a file, we can try the rm command to delete it quickly.

How to delete files in linux

## Introduction
When we use a linux system, we can quickly delete a folder through the `rm` command line,Delete all files and folders in the directory at the same time

This tutorial will teach youhow to delete a folder in linux

## Command Line
Cascading delete test files
```bash
rm -ir test
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| rm   |Remove one or more containers.|
| ps   |List containers.|
| -i   |prompt before every removal.|
| -r   |remove directories and their contents recursively.|

###  operation result
```
rm: remove directory 'test'? 
```

### Important reminder
It is recommended to delete the folder through -i to prevent direct deletion

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


When we use a linux system, we can quickly delete a folder through the rm command line.

how to delete a folder in linux

## Introduction
In the linux operating system, you can close the specified port through `firewall-cmd`

This tutorial will teach you How to close the port in linux

## Command Line
close port 8080
```bash
firewall-cmd --permanent --remove-port=8080/tcp
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| --permanent   |Set an option permanently Usable for options.|
| --remove-port   |Remove the port .|

###  operation result
```
success
```



#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


Open the command line tool in linux, you can use the firewall-cmd command line tool to quickly close the specified port.

How to close the port in linux

## Introduction
In the Linux operating system, you can use the `firewall-cmd` command line tool to open the specified port. After opening, other servers can connect to the port application specified by the device.
This tutorial will teach you how to delete all containers at once

## Command Line
Open port 3306
```bash
firewall-cmd --zone=public --add-port=3306/tcp --permanent
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| --zone   |Use this zone to set or query options, else default zone,Usable for options marked with|
| --add-port   |Add the port.|
| --permanent   |Set an option permanently.|

###  operation result
```
success
```

### safety warning
If your service is on a public network, you should increase the security protection applied to the specified port after opening the specified port.

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


Open the Linux command line program and use the firewall-cmd command to quickly open the specified port number.

how to open specified port in linux

## Introduction
In the Linux operating system, you can use the `firewall-cmd` command line tool to temporarily open the specified port for other server access

This tutorial will teach you How to open ephemeral ports in linux

## Command Line
Open port 3307
```bash
firewall-cmd --zone=public --add-port=3307/tcp
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| --zone   |Use this zone to set or query options, else default zone Usable for options marked with.|
| --add-port   |Add the port.|

###  operation result
```
success
```

### Important reminder
Open ports will be automatically closed after restart

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


Open the linux command line tool, use the firewall-cmd command line tool to quickly open the specified port, and automatically close after restarting.

How to open ephemeral ports in linux

## Introduction
In the Linux operating system, you can use the `firewall-cmd` command line tool to view the ports that have been opened in the current system and the corresponding transmission types

This tutorial will teach you How to check open ports in linux

## Command Line
View open UDP/TCP ports
```bash
firewall-cmd --list-ports --permanent
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| firewall-cmd   |a front-end tool for managing the firewalld daemon|
| --list-ports   |List ports added|
| --permanent   |Set an option permanently.|

###  operation result
```
8080/tcp
```
#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


First open the Linux terminal program, use the firewall-cmd command to view the open TCP and UDP ports in Linux, click to quickly learn how to use.

How to check open ports in linux

## Introduction
Linux was first written by Linus Benedict Torvalds in 1991. Before that, Richard Stallman founded the Free Software Foundation (FSF) organization and the GNU project, and continued to write and create GNU programs (the licenses for such programs are GPL: General Public License). The Linux we see today, or GNU/Linux, was created after the continuous addition of outstanding programmers and developers to the GNU organization.

Linux distributions can be roughly divided into two categories, one is the distribution maintained by commercial companies, the other is the distribution maintained by community organizations, the former is represented by the famous Redhat (RHEL), and the latter is represented by Debian

### Redhat
Redhat, which should be called the Redhat series, includes RHEL (Redhat Enterprise Linux, also known as Redhat Advance Server, paid version), Fedora Core (developed from the original Redhat desktop version, free version), CentOS (community clone of RHEL) version, free)
#### RedHat Linux
Red Hat Linux is the earliest personal version of Linux released by redhat, and its 1.0 version was released on November 3, 1994. Although it is not as old as other Linux distributions, Red Hat is much older than many Linux distributions. Since the release of Red Hat 9.0, Red Hat has stopped developing desktop Linux distributions, and Red Hat Linux has stopped developing, and concentrated on the development of the server version, which is Red Hat Enterprise Linux. On April 30, 2004, Red Hat officially stopped supporting the Red Hat 9.0 version, marking the official end of Red Hat Linux. The original desktop Red Hat Linux distribution was merged with the Fedora project from the open source community to become the Fedora Core distribution

#### Fedora Core
Fedora Core (abbreviated as FC) is positioned by Red Hat as an experimental site for new technologies. Many new technologies will be tested in FC. If it is stable, Red Hat will consider joining Red Hat Enterprise Linux.

#### Red Hat Enterprise Linux
Red Hat Enterprise Linux (abbreviated as RHEL, the enterprise version of Red Hat). Red Hat is now mainly engaged in the development of the server version of Linux, focusing on performance and stability as well as hardware support in the version. Due to the long development cycle of the enterprise version of the operating system, focusing on performance, stability and server-side software support, version updates are relatively slow.

#### Centos
CentOS is a free, open source, redistributed open source operating system. CentOS (Community Enterprise Operating System, which means community enterprise operating system in Chinese) is one of the Linux distributions.



### Debian
Ubuntu is a derivative of Debian and the most popular free operating system today. It is a Linux operating system based on desktop applications. An operating system built from free software. Ubuntu has a huge community strength, and users can easily get help from the community. On January 3, 2013, Ubuntu officially released a mobile operating system for smartphones.

### SUSE
The most popular LINUX in continental Europe originated in Germany and was acquired by Novell in late 2003. The main versions are: SUSE Linux, which can be downloaded for free for individual users;
Another is that SUSE Linux Enterprise Server (SLES) is based on the enterprise server side. If you need to use advanced database services and e-mail network applications, you can choose SUSE

### Gentoo
It is the youngest distribution in the Linux world. Because of its youth, it can absorb the advantages of all distributions before her. Gentoo was originally created by Daniel Robbins (one of the developers of FreeBSD), and the first stable version was released in 2002. Due to the developer's familiarity with FreeBSD, Gentoo has a widely-reputed ports system comparable to FreeBSD, the Portage package management system. Unlike package management systems such as APT and YUM that distribute binary files, Portage is distributed based on source code and must be compiled to run, which is slow for large-scale software, but because all software is compiled on the local machine, in After various customized compilation parameters are optimized, the hardware performance of the machine can be maximized. Gentoo is the most complicated to install among all Linux distributions, but it is also the most manageable version after installation, and it is also the fastest version under the same hardware environment.


There are multiple versions of Linux. This article teaches you how to choose the Linux version that suits you for a better experience.

Which linux version is right for you

## Introduction
In Linux, you can use the `ls` command to view file permissions

This tutorial will tell you how to check file permissions

## Command Line
View the permissions of all files in the current directory
```bash
ls -lah
```

## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| ls   |List information about the FILEs (the current directory by default).|
| -l   |use a long listing format.|
| -a   |do not ignore entries starting with .|
| -h   |with -l and -s, print sizes like 1K 234M 2G etc.|

###  operation result
```
total 0
drwxr-xr-x.  2 root root  32 Sep  6 21:43 .
dr-xr-xr-x. 18 root root 236 Sep  6 21:43 ..
-rw-r--r--.  1 root root   0 Sep  6 21:43 test1
-rw-r--r--.  1 root root   0 Sep  6 21:43 test2
```

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


In the Linux system, you can try the ls command to quickly view the file permissions.

How to check file permissions in linux

## Introduction
In `netlify`, how to create a new serverless `function`

This tutorial teaches you how to create a function

## Command Line
Create a `test` function
```bash
netlify function:create test
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| functions   |Manage netlify functions.|
| create   |Create a new function locally.|

###  operation result
```
? Select the type of function you'd like to create Serverless function (Node/Go)
? Select the language of your function JavaScript
? Pick a template javascript-hello-world
◈ Creating function test
◈ Created D:\code\test\netlify\functions\test\test.js
```

### Important reminder
You can choose different templates according to your needs

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


In netlify, how to create a new serverless function.

How to create new functions in netlify

### error message

Repository not found. Could not read from remote repository. Please make sure you have the correct access rights and the repository exists.


### solution

Go to project/.git and open the config file

find the following

```bash
[remote "origin"]
	url = git@github.com:/xxx/xxx.git
```

change into
```bash
[remote "origin"]
	url = https://github.com/xxx/xxx.git
```



Repository not found. Could not read from remote repository. Please make sure you have the correct access rights and the repository exists.

How to solve Repository not found in git

## Introduction
When using` docker` we may create a lot of containers, it will be very slow to delete one by one, you can delete all the containers at once by combining commands

This tutorial will teach you how to delete all containers at once

## Command Line
delete all containers
```bash
docker rm $(docker ps -a -q)
```
## Parameter Description
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| rm   |Remove one or more containers.|
| ps   |List containers.|
| -a   |Show all containers (default shows just running).|
| -q   |Only display container IDs.|
###  operation result
```
4b67fe5f30b5
cb7d3b455d05
```

### Important reminder
A running container cannot be deleted directly, you need to suspend the container before deleting

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


When using docker we may create a lot of containers, it will be very slow to delete one by one, you can delete all the containers at once by combining commands.

How to delete all containers at once in docker

## Introduction
The `docker` container will generate logs and store them locally. You can find the specified container and delete the corresponding log file.

This tutorial will teach you how to delete log files generated by docker containers

### Enter the docker container path
```bash
/var/lib/docker/containers/
```

### Enter the corresponding container directory
```bash
docker ps -a
```

### Enter the corresponding container directory
After entering or pasting the id, you can use tab to complete the directory
```bash
cd b8af02560de92655228155f96fa773038b298288061c1ba8dfa8b00f23bdc8e1
```

### delete log file
```
rm *.log
```

#### Notice
If you have any questions in use, you can leave a message below, or submit issuse on github ♥


The docker container will generate logs and store them locally. You can find the specified container and delete the corresponding log file.

How to delete logs of docker container

## Introduction
In docker, you can quickly delete one or more containers with the `rm` command
## Command Line
delete `mysql` container
```bash
docker rm mysql
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| rm   |Remove one or more containers.|
###  operation result
```
mysql
```
## More information
You can also delete by container id

### Notice
A running container cannot be deleted directly, you need to suspend the container before deleting


In docker, you can quickly delete one or more containers with the rm command

How to delete a container in docker

## Introduction
In docker, you can quickly stop all containers with the `stop` command
## Command Line
stop all containers
```bash
docker stop $(docker ps -q)
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| stop   |Stop one or more running containers.|
| ps   |List containers.|
| -q   |Only display container IDs.|

###  operation result
```
c8602711fb44
b8af02560de9
```


In docker, you can quickly pause all containers with the stop command

How to stop all containers in docker

## Introduction
In `docker`, you can quickly `delete` local `images` through rmi, which can be deleted by image id or image name

## Command Line
delete `mysql` image
```bash
docker rmi mysql
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| rmi   |Remove one or more images.|
###  operation result
```
Untagged: mysql:latest
Untagged: mysql@sha256:e9027fe4d91c0153429607251656806cc784e914937271037f7738bd5b8e7709
Deleted: sha256:3218b38490cec8d31976a40b92e09d61377359eab878db49f025e5d464367f3b
Deleted: sha256:aa81ca46575069829fe1b3c654d9e8feb43b4373932159fe2cad1ac13524a2f5
Deleted: sha256:0558823b9fbe967ea6d7174999be3cc9250b3423036370dc1a6888168cbd224d
Deleted: sha256:a46013db1d31231a0e1bac7eeda5ad4786dea0b1773927b45f92ea352a6d7ff9
Deleted: sha256:af161a47bb22852e9e3caf39f1dcd590b64bb8fae54315f9c2e7dc35b025e4e3
Deleted: sha256:feff1495e6982a7e91edc59b96ea74fd80e03674d92c7ec8a502b417268822ff
Deleted: sha256:8805862fcb6ef9deb32d4218e9e6377f35fb351a8be7abafdf1da358b2b287ba
Deleted: sha256:872d2f24c4c64a6795e86958fde075a273c35c82815f0a5025cce41edfef50c7
Deleted: sha256:6fdb3143b79e1be7181d32748dd9d4a845056dfe16ee4c827410e0edef5ad3da
Deleted: sha256:b0527c827c82a8f8f37f706fcb86c420819bb7d707a8de7b664b9ca491c96838
Deleted: sha256:75147f61f29796d6528486d8b1f9fb5d122709ea35620f8ffcea0e0ad2ab0cd0
Deleted: sha256:2938c71ddf01643685879bf182b626f0a53b1356138ef73c40496182e84548aa
Deleted: sha256:ad6b69b549193f81b039a1d478bc896f6e460c77c1849a4374ab95f9a3d2cea2
```


In docker, you can quickly delete local images through rmi, which can be deleted by image id or image name.

How to delete image in docker

## Introduction
There are a large number of high-quality `images` in the `docker` hub, which can be downloaded and used directly.
## Command Line
`Pull` the `mysql` image
```bash
docker pull mysql
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| pull   |Pull an image or a repository from a registry.|
###  operation result
```
Using default tag: latest
latest: Pulling from library/mysql
72a69066d2fe: Pull complete 
93619dbc5b36: Pull complete 
99da31dd6142: Pull complete 
626033c43d70: Pull complete 
37d5d7efb64e: Pull complete 
ac563158d721: Pull complete 
d2ba16033dad: Pull complete 
688ba7d5c01a: Pull complete 
00e060b6d11d: Pull complete 
1c04857f594f: Pull complete 
4d7cfa90e6ea: Pull complete 
e0431212d27d: Pull complete 
Digest: sha256:e9027fe4d91c0153429607251656806cc784e914937271037f7738bd5b8e7709
Status: Downloaded newer image for mysql:latest
docker.io/library/mysql:latest
```


There are a large number of high-quality images in the docker hub, which can be downloaded and used directly.

How to pull images in docker

## Introduction
You can use the `images` command to quickly view all local images in `docker`
## Command Line
View all local `images`
```bash
docker images
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| images   |List images.|
###  operation result
```
REPOSITORY    TAG       IMAGE ID       CREATED         SIZE
nginx         latest    605c77e624dd   7 months ago    141MB
mysql         latest    3218b38490ce   8 months ago    516MB
hello-world   latest    feb5d9fea6a5   11 months ago   13.3kB
```


You can use the images command to quickly view all local images in docker.

How to view local image in docker

## Introduction
When we use `docker`, we often encounter that the `memory` used by the `docker` container is larger than the `memory` of the `docker` host, which will cause the host to crash, resulting in shutdown, which can be prevented by limiting the container `memory`.
## Command Line
Start the `hello-world` container and limit the memory size to `1g`
```bash
docker run -d --name hello-world --memory 1G hello-world
```

## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| run   |Run a command in a new container.|
| -d   |Run container in background and print container ID.|
| --name   |Assign a name to the container.|
| --memory  |Memory limit.|

###  operation result
```
b8af02560de92655228155f96fa773038b298288061c1ba8dfa8b00f23bdc8e1
```

### Notice

The current configuration is only used for testing, if you want to use it in a production environment, you need to adjust it according to your needs 


When we use docker, we often encounter that the memory used by the docker container is larger than the memory of the docker host, which will cause the host to crash, resulting in shutdown, which can be prevented by limiting the container memory.

How to present the memory of a docker container

## Introduction
In centos8, we can quickly install docker through `yum`

### Preparation
Uninstall historical versions of docker
```bash
sudo yum remove docker \
                  docker-client \
                  docker-client-latest \
                  docker-common \
                  docker-latest \
                  docker-latest-logrotate \
                  docker-logrotate \
                  docker-engine
```

Install yum-utils
```bash
sudo yum install -y yum-utils
```

Uninstall the built-in podman
```bash
sudo yum erase podman buildah
```

### Install

Add repository
```bash
sudo yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo
```

install docker
```bash
sudo yum install docker-ce docker-ce-cli containerd.io docker-compose-plugin
```

docker starten
```bash
systemctl start docker
```
 
Start einstellen
```bash
systemctl enable docker
```
Test
```bash
sudo docker run hello-world
```



In centos8, we can quickly install docker through yum

How to install docker in Centos8

## Introduction
In linux, you can use the `tail` command to view the content of the last few lines of the file
## Command Line
View the last `3` lines of the `target.txt` file
```bash
tail -3 target.txt
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| tail   |Print the last 10 lines of each FILE to standard output.|
| -n   |output the last NUM lines, instead of the last 10.|
###  operation result
```
8
9
10
```


In linux, you can use the tail command to view the content of the last few lines of the file

How to view the last few lines of a file in linux

## Introduction
In linux, you can use `curl` to quickly download files and save them locally
## Command Line
Download `https://github.com` webpage and save it to local `github.html`
```bash
curl https://github.com -o github.html
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| curl   |is  a tool to transfer data from or to a server, using one of the
       supported protocols (DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS,  IMAP,
       IMAPS,  LDAP,  LDAPS,  POP3,  POP3S,  RTMP, RTSP, SCP, SFTP, SMB, SMBS,
       SMTP, SMTPS, TELNET and TFTP). The command is designed to work  without
       user interaction.|
| -o  |Write to file instead of stdout|
###  operation result
```
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   161  100   161    0     0   1412      0 --:--:-- --:--:-- --:--:--  1412
```


In linux, you can use curl to quickly download files and save them locally

How to download files in linux

## Introduction
In Linux systems, you can quickly write text to a file through `echo`
## Command Line
Add `add test` to the end of the file `target.txt`
```bash
echo "add test" >> target.txt
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| echo   |Print the value of the shell variable in the shell, or directly output the specified string.|
###  operation result
```

```


In Linux systems, you can quickly write text to a file through echo

How to add text to file in linux

## Introduction
In linux system, you can rename a file or folder by `mv`
## Command Line
Rename the `text.txt` file to `target.txt`
```bash
mv text.txt target.txt
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| ls   |Rename SOURCE to DEST, or move SOURCE(s) to DIRECTORY.|
###  operation result
```

```


In linux system, you can rename a file or folder by mv

How to change file name in linux

## Introduction
In linux system, you can quickly switch users through `su`
## Command Line
Switch user to **cmdhelp**
```bash
su cmdhelp
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| su   |Change the effective user ID and group ID to that of \<user\>.|
###  operation result
```
Password: 
```


In linux system, you can quickly switch users through su

How to switch users in linux

## Introduction
In linux system, you can check the current time through the `date` command
## Command Line
View current system date
```bash
date
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| date   |Display the current time in the given FORMAT, or set the system date.|
###  operation result
```
Tue Aug 23 14:28:36 CST 2022
```


In linux system, you can check the current time through the date command

How to check the current time in linux

## Introduction
In linux, you can use the `ip` tool to view the private ip address of the current device
## Command Line
View private ip address
```bash
ip addr
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| ip   |show / manipulate routing, network devices, interfaces and tunnels.|
| addr |Shows addresses assigned to all network interfaces .|
###  operation result
```
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens160: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:14:e9:62 brd ff:ff:ff:ff:ff:ff
    altname enp3s0
    inet 192.168.91.135/24 brd 192.168.91.255 scope global dynamic noprefixroute ens160
       valid_lft 1158sec preferred_lft 1158sec
    inet6 fe80::20c:29ff:fe14:e962/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 52:54:00:6d:26:ba brd ff:ff:ff:ff:ff:ff
    inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0
       valid_lft forever preferred_lft forever
```


In Linux system, you can view hidden files or folders by ls command

How to check private ip in linux

## Introduction
In linux, we can request some ip query interface through `curl` to view the current public `ip` address
## Command Line
View current ip address
```bash
curl ifconfig.me
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| curl   |is  a  tool to transfer data from or to a server, using one of the supported protocols (DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS,
       POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET and TFTP). The command is designed to work without user interaction.|
###  operation result
```
x.22.85.x
```
### More information
You can also query through these URLs
```bash
curl ipinfo.io/ip
curl api.ipify.org
curl checkip.dyndns.org
curl ident.me
curl bot.whatismyipaddress.com
curl ipecho.net/plain
```


In linux, we can request some ip query interface through curl to view the current public ip address

How to check your public ip address in linux

## Introduction
This tutorial introduces the quick installation of `kafka` in the `centos8` environment. You can install kafka smoothly by following the steps in the tutorial

### Preparation

1. Install the `java` environment
2. Download the `kafka` package：http://kafka.apache.org/downloads

### Installation tutorial

Unzip the downloaded file
```bash
tar -zxf kafka_2.12-3.2.1.tgz
```

Enter the decompressed kafka directory 

```bash
cd kafka_2.12-3.2.1/
```
Create the zookeeper data storage directory
```bash
mkdir -p zk/data
```
Create zookeeper log storage log directory
```bash
mkdir -p zk/logs
```
Enter the configuration directory
```bash
cd config
```

Backup zookeeper configuration file
```bash
mv zookeeper.properties zookeeper.properties.bak
```
Create configuration file
```bash
cat > zookeeper.properties << EOF
tickTime=2000
dataDir=/home/cmdhelp/test/kafka_2.12-3.2.1/zk/zk/data
dataLogDir=/home/cmdhelp/test/kafka_2.12-3.2.1/zk/zk/logs
clientPort=2181
EOF
```

Enter the kafka directory
```bash
cd /home/cmdhelp/test/kafka_2.12-3.2.1
```

Create log directory
```bash
mkdir logs
```
Go to the configuration file directory
```bash
cd config
```
Backup configuration files
```bash
mv server.properties server.properties.bak
```
Create configuration file
```bash
cat > server.properties << EOF
broker.id=1
listeners=PLAINTEXT://192.168.91.135:9092
num.network.threads=3
num.io.threads=8
socket.send.buffer.bytes=102400
socket.receive.buffer.bytes=102400
socket.request.max.bytes=104857600
log.dirs=/home/cmdhelp/test/kafka_2.12-3.2.1/logs
num.partitions=1
num.recovery.threads.per.data.dir=1
offsets.topic.replication.factor=1
transaction.state.log.replication.factor=1
transaction.state.log.min.isr=1
log.retention.hours=168
log.segment.bytes=1073741824
log.retention.check.interval.ms=300000
zookeeper.connect=192.168.91.135:2181
zookeeper.connection.timeout.ms=6000
group.initial.rebalance.delay.ms=0
EOF
```
start zookeeper
```bash
/home/cmdhelp/test/kafka_2.12-3.2.1/bin/zookeeper-server-start.sh -daemon /home/cmdhelp/test/kafka_2.12-3.2.1/config/zookeeper.properties
```
start kafka
```bash
/home/cmdhelp/test/kafka_2.12-3.2.1/bin/kafka-server-start.sh -daemon /home/cmdhelp/test/kafka_2.12-3.2.1/config/server.properties 
```

ps:The installation is complete, it should be noted that the Java environment must be installed to start normally

### other operations
Shut down the zookeeper service
```bash
/home/cmdhelp/test/kafka_2.12-3.2.1/bin/zookeeper-server-stop.sh
```
Close the kafka service
```bash
/home/cmdhelp/test/kafka_2.12-3.2.1/bin/kafka-server-stop.sh
```




This tutorial introduces the quick installation of kafka in the centos8 environment. You can install kafka smoothly by following the steps in the tutorial

How to install kafka in centos8

## Introduction
In centos8, `jdk` can be quickly installed through `yum`
## Command Line
Install `jdk` using the `yum` tool
```bash
yum install -y java-1.8.0-openjdk
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| yum   |a package manager.|
| install   |install a package or packages on your system.|
###  operation result
```
...
Complete!                 Output a full package dependency graph in dot format
```


In centos8, jdk can be quickly installed through yum

How to install jdk in centos8

## Introduction
In linux, you can connect to other servers through the `ssh` command
## Command Line
Connect to the `192.168.91.135` server and log in with the `root` account
```bash
ssh root@192.168.91.135
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| ssh   |provides a secure encrypted connection between two hosts over an insecure network.|
###  operation result
```
...
Last login: Mon Aug 22 19:21:04 2022
```


In linux, you can connect to other servers through the ssh command

How to connect to a remote server in linux

## Introduction
In Linux, you can copy files to a remote server through the `scp` command
## Command Line
Copy the `kafka_2.12-3.2.1.tgz` file to the `/home/cmdhelp/test` directory of the remote server `192.168.91.135`
```bash
scp kafka_2.12-3.2.1.tgz root@192.168.91.135:/home/cmdhelp/test
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| scp   |Commands to copy files remotely under Linux.|
###  operation result
```
root@192.168.91.135's password:
kafka_2.12-3.2.1.tgz                                                                  100%   99MB  74.7MB/s   00:01
```


In Linux, you can copy files to a remote server through the scp command

How to copy files to remote server in linux

## Introduction
In Linux, you can quickly create multi-level directories through `mkdir`
## Command Line
Create a multilevel directory `zk/data`
```bash
mkdir -p zk/data
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| mkdir   |Create the DIRECTORY(ies), if they do not already exist.|
| -p   |no error if existing, make parent directories as needed.|
###  operation result
```

```


In Linux, you can quickly create multi-level directories through mkdir

How to create a multi-level directory in linux

## Introduction
In linux, you can use the `tar` command to decompress files in tgz format
## Command Line
Unzip the `kafka_2.12-3.2.1.tgz` file
```bash
tar -zxf kafka_2.12-3.2.1.tgz
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| tar   |GNU 'tar' saves many files together into a single tape or disk archive, and can
restore individual files from the archive.|
| -z  |filter the archive through gzip.|
| -x   |extract files from an archive.|
| -f   |use archive file or device ARCHIVE.|

###  operation result
```

```


In linux, you can use the tar command to decompress files in tgz format

How to decompress tgz file in linux

## Introduction
In linux, you can use the `pwd` command to view the current path.
## Command Line
View the current path
```bash
pwd
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| pwd   |    Print the name of the current working directory.|

###  operation result
```
/home/cmdhelp/test
```


In linux, you can use the pwd command to view the current path.

How to check the current path in linux

## Introduction
In Linux system, you can view hidden files or folders by `ls` command
## Command Line
View all files in the current directory
```bash
ls -a
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| ls   |List information about the FILEs (the current directory by default).|
| -a   |do not ignore entries starting with .|
###  operation result
```
.  ..  .hide
```


How to view hidden files in linux

## Introduction
In linux, you can use the `crontab` command to view all the scheduled tasks of the current user
## Command Line
View automated tasks for the current user
```bash
crontab -l
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| crontab   |scheduled tasks.|
| -l   |list user's crontab.|
###  operation result
```
no crontab for root
```


In linux, you can use the crontab command to view all the scheduled tasks of the current user

How to view scheduled tasks in linux

## Introduction
In git, you can quickly add submodules through `submodules`
## Command Line
Add the remote repository `command` to the `command` path of the current project
```bash
git submodule add https://github.com/cmdhelp/command.git command/
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| git   |free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.|
| submodule   |Initialize, update or inspect submodules.|
###  operation result
```
Cloning into 'D:/code/test/command'...
remote: Enumerating objects: 120, done.
remote: Counting objects: 100% (120/120), done.
remote: Compressing objects: 100% (106/106), done.
remote: Total 120 (delta 31), reused 10 (delta 0), pack-reused 0
Receiving objects: 100% (120/120), 26.57 KiB | 2.95 MiB/s, done.
Resolving deltas: 100% (31/31), done.
warning: LF will be replaced by CRLF in .gitmodules.
The file will have its original line endings in your working directory
```


In git, you can quickly add submodules through submodules

How to add submodules in git

## Introduction
In linux, you can quickly create a file by `touch`
## Command Line
Create a file called `text.txt`
```bash
touch text.txt
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| touch   |Update the access and modification times of each FILE to the current time.|
###  operation result
```
```


In linux, you can quickly create a file by touch

How to Create a File in Linux

## Introduction
In linux, you can quickly create a new user with `adduser`

## Command Line
Create a user named `cmdhelp`
```bash
sudo adduser cmdhelp
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| sudo   |execute a command as another user|
| adduser   |Add user.|

###  operation result
```

```


In linux, you can quickly create a new user through adduser

How to create user in linux

## Introduction
In linux, you can quickly change user passwords through `passwd`
## Command Line
Change the password of the user `cmdhelp`
```bash
sudo passwd cmdhelp
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| sudo   |execute a command as another user|
| passwd |set password.|

###  operation result
```
[sudo] password for root: 
Changing password for user cmdhelp.
New password: 
BAD PASSWORD: The password is shorter than 8 characters
Retype new password: 
passwd: all authentication tokens updated successfully.
```
### Notice
If the password is less than 8 digits, you can continue to enter it for the second time.







In linux, you can quickly change user passwords through passwd

How to Change the Password of a Specified User in Linux

## Introduction
In linux, you can try the `wc` command to quickly count the number of lines in a file
## Command Line
In the demo we count the number of lines in the `test.txt` file
```bash
wc -l test.txt
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| wc   |Print newline, word, and byte counts for each FILE, and a total line if more than one FILE is specified.  A word is a non-zero-length sequence of characters delimited by white space.|
| -l   |print the newline counts.|
###  operation result
```
4 test.txt
```


In linux, you can quickly move folders through the command line mv, or you can modify the folder name through mv

How to count the number of lines in a file in linux

## Introduction
Find files containing strings via `grep`

In the demo, look for the file containing `find test` in the `/home/cmdhelp/test` directory

## Command Line
```bash
grep -rnw /home/cmdhelp/test -e 'find test'
```
## Parameter
| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| grep   | Search for PATTERN in each FILE. |
| -n   | print line number with output lines. |
| -r   | like --directories=recurse. |
| -w   | force PATTERN to match only whole words. |
| -e   | use PATTERN for matching. |
###  operation result
```
/home/cmdhelp/test/test.txt:4:find test
```


In linux, you can try the grep command to find files containing strings

How to find files containing strings in linux

## Introduction

You can move files or folders with the mv command

## Command Line
Move `testdir1` to `testuser1`
```bash
mv testdir1 testuser1
```

## Parameter

| parameter | Introduction                                                               |
| --------- | -------------------------------------------------------------------------- |
| mv   | path to data files to supply the data that will be passed into templates. |

###  operation result
```
```
