APT package management

The simplified event flow of the package management by APT:

• Update ("apt update", "aptitude update" or "apt-get update"):
1. Fetch archive metadata from remote archive
2. Reconstruct and update local metadata for use by APT


• Upgrade ("apt upgrade" and "apt full-upgrade" or "aptitude safe-upgrade" and "aptitude full-upgrade" or "apt-get upgrade" and "apt-get dist-upgrade"):
1. Chose candidate version which is usually the latest available version for all installed packages
2. Make package dependency resolution
3. Fetch selected binary packages from remote archive if candidate version is different from installed version
4. Unpack fetched binary packages
5. Run preinst script
6. Install binary files
7. Run postinst script


• Install ("apt install ...", "aptitude install ..." or "apt-get install ..."):
1. Chose packages listed on the command line
2. Make package dependency resolution
3. Fetch selected binary packages from remote archive
4. Unpack fetched binary packages
5. Run preinst script
6. Install binary files
7. Run postint script


• Remove ("apt remove ...", "aptitude remove ..." or "apt-get remove ..."):
1. Chose packages listed on the command line
2. Make package dependency resolution
3. Run prerm script
4. Remove installed files except configuration files
5. Run postrm script


• Purge ("apt purge ...", "aptitude purge ..." or "apt-get purge ..."):
1. Chose packages listed on the command line
2. Make package dependency resolution
3. Run prerm script
4. Remove installed files including cinfiguration files
5. Run postrm script