Install jdk

Go to the official website to download the rpm package of jdk
Install JDK
1. First transfer the software to linux through xftp
2. Installation

rpm -ivh jdk-8u281-linux-x64.rpm 

3. Configure the configuration file vim /etc/profile of environment variables

JAVA_HOME=/usr/java/jdk1.8.0_281-amd64
PATH=/usr/java/jdk1.8.0_281-amd64/bin:$PATH
export JAVA_HOME PATH

Reload profile
source /etc/profile
 test
java
javac
java -version

Install tomcat

Go to the official website to download tomcat's tar GZ bag Transfer to linux through xftp
decompression
tar -zxvf xxx.tar.gz
Enter the bin directory in tomcat and run tomcat
./start.sh
Open port 8080 so that the external network can access it
firewall-cmd --add-port=8080/tcp --permanent
Test for successful installation:
Access under windows http://linuxip:8080

Python custom apt software management and remote login

Apt is the abbreviation of Advanced Packaging Tool, which is an installation package management tool. Under Ubuntu, we can use apt command to install, delete and clean software packages, which is similar to the software management tool in Windows.

Update source

Open with an editor you are familiar with:
/etc/apt/sources.list

ubuntu 20.04(focal) The configuration is as follows
deb http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe multiverse

Commands related to software operation

sudo apt-get install package Installation package
sudo apt-get remove package Delete package
sudo apt-cache search package Search package
sudo apt-cache show package	Get package related information, such as description, size, version, etc
sudo apt-get install package --reinstall	Reinstall package
sudo apt-get -f install	Repair installation
sudo apt-get remove package --purge Delete packages, including configuration files, etc
sudo apt-get build-dep package Install the relevant compilation environment

sudo apt-get upgrade Update installed packages
sudo apt-get dist-upgrade Upgrade system
sudo apt-cache depends package Understand which packages are dependent on using this package sudo apt-cache rdepends package View which packages the package depends on sudo apt-get source package	Download the source code of the package

The so-called image source: it can be understood as a place where software can be downloaded, such as the Android Market where software can be downloaded on Android phones; App store where software can be downloaded on iOS phones

Remote login to Ubuntu Using ssh
ssh introduction
SSH is the abbreviation of Secure Shell, which is developed by the Network Working Group of IETF; SSH is a security protocol based on application layer and transport layer.
SSH is a reliable protocol that provides security for remote login sessions and other network services. It is often used for remote login and data copying between users. SSH can be run on almost all UNIX platforms including HP-UX, Linux, AIX, Solaris, Digital UNIX, Irix, and others.
To use SSH service, you need to install the corresponding server and client. Relationship between client and server: if machine A wants to be used by B
If the machine is controlled remotely, machine A needs to install ssh server and machine B needs to install SSH client.
Unlike CentOS, Ubuntu does not have the SSHD service installed by default, so we cannot log in remotely.

Remote login to Ubuntu Using ssh
Install SSH and enable
sudo apt-get install openssh-server
After executing the above instructions, install the SSH server and client on the current Linux.
service sshd restart
Execute the above instructions to start the sshd service. Will listen on port 22

ssh username @ IP
For example: ssh atguigu@192.168.188.131
Use SSH to access. If there is an error accessing. Check whether the file ~ / ssh/known_ssh tried to delete the file.
Logout
Logout command: exit or logout

The authenticity of host '192.168.0.107 (192.168.0.107)' can't be established.
ECDSA key fingerprint is SHA256:Brov9TgYfZIDvDHaxqtWzXKvhA52Ud9Wf5f3TX0NyDY.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.0.107' (ECDSA) to the list of known hosts.
xuebiao@192.168.0.107's password:
Welcome to Ubuntu 20.04.1 LTS (GNU/Linux 5.8.0-43-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage


332 updates can be installed immediately.
136 of these updates are security updates.
To see these additional updates run: apt list --upgradable

Your Hardware Enablement Stack (HWE) is supported until April 2025.
Last login: Fri Feb 19 16:28:45 2021 from 192.168.0.178
xuebiao@xuebiao-VirtualBox:~$