Basic Linux

Advanced Packaging Tool, APT

APT is a package management tool used in Debian and its derivatives (such as Ubuntu). It automatically resolves package dependencies, allowing users to install, update, and remove software with simple commands. This greatly simplifies the process of managing system software.

Update & Upgrade

In an Ubuntu system, the difference between APT update and APT upgrade is as follows:

• APT update: This command downloads the latest package lists from the configured software sources, updating the local package database. It does not install or upgrade any software; it simply informs the system about which packages have newer versions available.
• APT upgrade: This command upgrades the installed software packages to their latest available versions, based on the updated package list. In other words, you first run apt update to refresh the package information, and then use apt upgrade to actually apply the software updates.

Package Name

Method 1: apt search

apt search <key-word>

Method 2: dpkg search

which <command>

dpkg -S <return-by-which-command>

Remove

sudo apt remove <package-name>

Secure Shell, SSH

Asymmetric Cryptography

SSH is an encrypted communication protocol mainly used to provide secure remote login and data transfer over unsecured networks. Through SSH, users can securely access and manage remote systems, ensuring the confidentiality and integrity of data during transmission.

Asymmetric cryptography, also known as public-key cryptography, uses a pair of keys (a public key and a private key) for data encryption and digital signatures. This technology is widely used for secure communication, authentication, and digital signing, ensuring the confidentiality and integrity of data during transmission.

Two common use cases of asymmetric cryptography:

• Sending a message to the key pair owner: The sender encrypts the message using the recipient's public key, and the recipient decrypts it with their private key. This ensures confidentiality, as only the intended recipient can read the message.