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1. Install NTP server2. Install FTP Server2.1 Install Vsftpd

Create public and private key pairsCreate a public/private key pair for a user connecting to a Linux server using OpenSSH.Use ssh-keygen to create the key pair.This time, we will create a key set using the RSA cipher used in the SSH protocol Version 2.The creation of a public/private key pair is performed with remote login user privileges (e.g., huong).If you do not specify the destination and file name, id_rsa and id_rsa.pub will be created in /home/huong/.ssh/. On the way, enter the password for the key.

1. SSH Service Security SettingsThe SSH service allows the root user to log in by default, and since the root user already knows the user name and can log in to the server with administrative privileges once the password is known, we will deny this setting.1.1 Creating a General UserIf you have created a general user when installing Debian, this procedure is not necessary.If the only user created on the server is root, remote login via SSH will not be possible, so if a user has not been created during OS installation, a user must be created in advance.Users can be created with the "useradd" command. The "-m" option creates a home directory and the "-p" option specifies the password.For example, to set "debianuser" as the user account name and "123456" as the password, execute the following

1.Installing and configuring the vim editorDebian has "nano" as the default editor. nano is somewhat difficult to use, and there are few environments where it is used, so we will introduce the procedure for changing the editor to "vim".。1.1 Check vim packageDebian has vim installed by default, but it is a package called "vim-tiny", which is a less functional version. Let's check the installed vim package.Debian uses the "dpkg" command to check packages. The "-l" option displays a list of packages.Since the "dpkg" command as is will show all packages installed on the system, we will use the "grep" command to extract only those packages that contain the string "vim". Execute as follows

1.Install SNORT2Snort is an open source network intrusion detection system capable of performing real-time traffic analysis and packet logging on IP networks.It can perform "protocol analysis," "content search," and "matching," and can be used to detect a variety of attacks, including "buffer overflows," "stealth port scans," "CGI attacks," "SMB probes," "OS fingerprinting attempts," "semantic URL attacks," and "server message block probes.2.Install TripwireImplement a system to detect file tampering on Linux servers by crackers.This time, Tripwire, a host-based IDS (IDS=Intrusion Detection System), will be installed as the file tampering detection system.Tripwire creates a database of file status at the time of installation, and detects file additions/changes/deletions by comparing the database with the current status of the file.

1. System Backup1.1 Backup under /var/www/html①　Create backup_all.sh script under /opt1.2 Mysql database backup①Create db_backup.sh script under /opt# vi /opt/db_backup.shdb_backup.sh script contents2. System Restore2.1 Restore backup files under HTML① Store HTML backup files used for backup in the "/ (root)" directorySelect the backup file with the latest timestamp (e.g. www_back_20220501.tar.gz)2.2 Restore MySQL database①Save DB backup file to any directory and extract data# cd /var/www/backup/db_bak

1. Obtain a certificate (Let's Encrypt)1.1 advance preparation①Enable mod_ssl# a2enmod ssl2. SSL/TLS (Let's Encrypt) configuration for Apache2①Edit Apache2 SSL-related configuration files3. SSL/TLS (Let's Encrypt) settings on the mail server3.1 Obtaining a certificate for the mail serverObtain a certificate for the mail server, but it cannot be obtained in the same way as above, so the following with the "--standalone" option fails.