Create a virtual machine in three steps
1. Install Linux hardware
1. Select Custom, click Next
2. Continue to the next step
3. The next step prompts to install the operating system, we first install the hardware and then install the operating system
4. Select the Linux operating system, and then select CentOs7 64-bit in the version
5. Give the virtual machine a name, name it Cryptography here, and choose your own installation location
6. Configure the parameters of the processor, do not exceed the total number of CPUs of the local computer, my CPU has eight (how to check the number of CPUs? See the picture below 1 and Figure 2), so configure like this
Configure the processor of the virtual machine
7. Configure the memory of the virtual machine, I choose 4G, click Next
8. Network type, select NAT, select bridge may cause insufficient ip address 
9. Select recommended , click Next
10. Select Recommended, click Next
11. Select Create New Virtual Machine
12. Select Split
13. Select Path
15. Click Finish
Two, Linux installation software
1. Install the image, click OK
2. Then start the virtual machine
3. Set language
4. Select the date and time
5. Come to the software selection, select the desktop installation
7. Select the installation location
, select the partition I want to configure, and then click Finish
to continue adding the mount node
Click Finish to accept the changes
8. Configure the network and host name
9. Check whether the security policy is enabled, generally it is enabled by default
10. Turn on the virtual machine
11. We can set the root password during the installation of the virtual machine 12.
Restart after the installation is complete
.click permission
Click to complete the configuration
14. Click forward until the time zone appears
15. Click Skip
16. Set username and password, then go forward
17. Then enter the Linux graphical operating system, click Edit
to modify the gateway
18. Modify the Ethernet adapter option locally,
select 4, double-click
19 modify ip
#先切换到root用户下命令
su root
#进入网络设置命令
vim /etc/sysconfig/network-scripts/ifcfg-ens33
20. Modify the host name
#修改主机名称
vim /etc/hostname
21. Restart
22. Check the network and test whether the network is smooth
3. Remote connection
Other appearance settings can be set according to your own preferences
Four, Xshell link Ubuntu error
When Xshell cannot connect to Ubuntu, first try the command to check whether your ip is entered correctly
ifconfig
Then check whether your network is unobstructed, use the command
ping www.baidu.com
Download related dependencies, execute the following command
sudo apt install poenssh-ser
Re-execute
sudo service ssh start
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