ubuntu20.04 server 安装教程

### Ubuntu 20.04 Server Installation Guide

#### Preparing for the Installation

Before starting with the installation of any software or service on an Ubuntu 20.04 server, ensuring that all system packages are up-to-date is crucial. This can be achieved by executing commands which update the package lists and upgrade installed packages:

sudo apt-get update && sudo apt-get upgrade -y

#### Installing Composer

For installing Composer—a dependency manager for PHP projects—on an Ubuntu 20.04 server involves several steps including downloading the installer script from the official website and verifying its integrity using GPG keys[^1]. After successful verification, moving the Composer binary into a directory within your PATH ensures it's globally available.

#### Setting Up PostgreSQL Database

To set up PostgreSQL on this version of Ubuntu, one begins by adding the project’s APT repository followed by updating local package indexes before actually installing PostgreSQL itself through `apt`. Initial setup includes creating roles and databases as well as configuring remote access settings if necessary[^2].

#### Configuring MariaDB Securely

Installing MariaDB follows similar patterns but focuses more heavily on securing installations post-installation via scripts provided specifically for hardening default configurations against common vulnerabilities such as removing anonymous users or disallowing root logins remotely[^3].

#### Managing Access Through SSH

Given that managing servers often requires secure communication channels like those offered by SSH (Secure Shell), setting up key-based authentication instead of password-based methods enhances security significantly while reducing risks associated with brute force attacks aimed at gaining unauthorized entry points into systems managed over networks[^4].

--related questions--

1. What specific measures should be taken when securing a newly installed instance of MySQL/MariaDB?
2. How does adding repositories impact the stability and security of my Linux distribution during updates?
3. Can you provide detailed instructions on generating SSH keys for accessing remote servers securely without passwords?
4. In what ways do Composer dependencies differ between different versions of PHP applications hosted on Ubuntu servers?