17.7.2 “apt-get update” command – Update Local Package DB
The “update” command is used to update the program package information in the local package repositoroty installed on the system to the latest version. When this command is executed, the package information stored in the local package repository is updated to the latest version, and the latest package file for the installed program is downloaded and archived.
17.7 Update and Upgrade of Program
17.7.1 Upgarde of Program
The package managed by the package repository manages software distribution and metadata in the form of archive files. When a package is installed on a specific computer, the metadata contained in the package is stored in the local package database. In this local package database, typical information such as software dependency and version is managed. The package manager uses this local package database to prevent discrepancies between software and missing essential items.
17.6.2 Cleaning Program Package File
During the process of installing or upgrading programs, the related program package file is downloaded and stored in the local repository “/var/cache/apt/archives/”. These files are not deleted and remain intact even if the program installation is completed or the program is removed. If these files continue to accumulate, it will take up unnecessary storage space in the system, so it’s a good idea to remove any files that is no longer needed.
17.6 Uninstalling Programs and Cleaning Files
17.6.1 Uninstalling Programs
If you no longer need the installed programs, you should remove them. There are several ways to remove installed programs.
17.5 Installing and Reinstalling Program
17.5.1 Comparison of Installation by Source Distribution Method
In the Raspbian operating system, it is standard to manage and distribute programs using the package repository, but you can distribute, install, and use programs without using this method.
17.5.2 Installing Programs Distributed in Package Repository
● “apt-get install” command – install program
When installing programs in the package repository, use “install” command in “apt-get” command.
17.5.3 Installing Programs Distributed in Package Format
Of course, if the program is configured in a package format but is not registered in the package repository and distributed in a separate way, you can not use the APT tool “apt-get” command, and you have to use the low-level “dpkg” command.
17.5.4 Installing Programs Distributed in the General File Format
Among the developed programs, programs that are composed in the form of general source code or executable files other than the form of packages are not registered and distributed in the package repository, and those should be distributed and installed in a separate way.
17.4.3 How to Download from Internet Using GitHub
Finally, there are programs that provide source program in the GitHub. GitHub provides the tool that allows developers to securely manage the source code of development program in the process of developing, deploying, and later managing open source programs and manage versions of subsequent modifications from development to post-management. The programs that are managed here are kept in the GitHub repository, and you can always download and use the source code for those who need it.
17.4.2 How to Download from Internet with “wget” Command
We occasionally download and install programs directly from the Internet. In this case, you can also download the program directly from the web browser, but you can download the necessary program by specifying the URL directly in the Shell Terminal of Raspberry Pi. The command to use in this case is the “wget” command.