Ubuntu 20.04 desktop installation and root permission activation and ssh installation details

The article mainly records the simple installation process of Ubuntu 20.04, replaces the domestic source after installation, installs openssh software, and enables root privilege login

Ubuntu 20.04 installation

The installation is relatively simple. After loading the image file, just follow the steps step by step.

Link: Ubuntu 20.04 installation detailed tutorial Follow this document to install successfully.

After successful installation, log in using the username used during the installation process.

After logging in, update the domestic source first. Here, choose Alibaba, or you can choose others.

This will update the source, and the subsequent installation of related software will be much faster.

ssh installation

Install ssh

sudo apt-get update
sudo apt-get install openssh-server

Set up SSH login for the root user

Modify the configuration file: /etc/ssh/sshd_config

Find the following settings

 Authentication: 
# LoginGraceTime 2m 
# PermitRootLogin prohibit-password 
# StrictModes yes

Replace with

# Authentication: 
LoginGraceTime 120 
#PermitRootLogin prohibit-password 
PermitRootLogin yes 
StrictModes yes

Restart the service

sudo /etc/ini.d/ssh restart

After the setup is complete, log in using ssh (username)@(IP).
Found that I couldn't log in

sudo systemctl status ssh

After checking, it was found that the error was error: kex protocol error:
To solve this problem, open the /etc/ssh/sshd_config configuration file and add the following code segment at the end

KexAlgorithms [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group14-sha1

Then restart the ssh service. At this point, you can log in to ssh using your username, but root still cannot.

Enable root user

1. First Step

Log in to the system as a normal user, create a password for the root user, and enter the command in the terminal: sudo passwd root

Then enter the set password twice, and the root user password is set (note that the password is not echoed in Linux system)

Step 2

Modify the 50-ubuntu.conf file

Enter the command in the terminal: sudo vim /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf
Add the following two lines to the end of the file:

greeter-show-manual-login=true
all-guest=false

Step 3

Modify the gdm-autologin file

Enter the command in the terminal: sudo vim /etc/pam.d/gdm-autologin
Open the file and add # in front of it. Comment out the third line: auth required pam_succeed_if.so user != root quiet_success

Step 4

Modify the gdm-password file

Enter the command in the terminal: sudo vim /etc/pam.d/gdm-password Open the file and add # in front of it. Comment out the third line: auth required pam_succeed_if.so user != root quiet_success

Step 5

Modify the /root/.profile file. Enter the command in the terminal: sudo vim /root/.profile Open the file and modify the line mesg n 2> /dev/null || true at the end of the file to
tty -s&&mesg n || true
Finally, restart the server.

After the reboot, you can log in as root or as your username.

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