Apt update and apt upgrade commands - what is the difference?

In the previous post , We checked APT Commands and various methods that you can use the package manager to manage packages . This is a general overview , But in this guide , We pause and focus on 2 Command usage . These are apt update and apt upgrade command .

apt update and apt upgrade It's a lot of Linux Two commands most commonly used by users but misunderstood . For some people , They play the same role , But that's not the case . In this guide , We try to distinguish between the two and how to use them .

1）apt update command

This is a command that is mainly called after the installation of a new system or before the installation of a new software package .apt update The command to update Linux Package index or package list of the system . It will not upgrade any packages , Just like some Linux Users are misled .

/etc/apt/sources.list A package index file is a file or database , It contains a list of packages defined in the repository located in the file . The list of other packages is located at /etc/apt/sources.list.d  Directory .

Running this command is very safe . If the power supply is suspended or unplugged for some reason , You can recover from where you stopped .

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Use... On the terminal cat Command to view the source list file .

$ cat /etc/apt/sources.list

/etc/apt/sources.list file

To update the package list , Please call the following command ：

about Ubuntu 18.04 And higher

$ sudo apt update

about Ubuntu 16.04 And earlier

$ sudo apt-get update

2）apt upgrade command

You need to upgrade your software package to the latest version ？ then apt upgrade It's an order to execute .apt upgrade The command takes no parameters , Upgrade all outdated software packages on the system to the latest version .

If you need any dependencies , This command will also trigger the installation of new software packages . besides ,apt upgrade It will also install all the security updates required for your system , This strengthens the security of your system .

List the packages that need to be upgraded , Please run apt list --upgradable command . in fact , This is apt update The last displayed prompt of the output .

therefore , To view the packages ready for upgrade , Please run ：

$ sudo apt list --upgradable

Upgrade all outdated software packages and apply security patches , Please run the following command ：

$ sudo apt upgrade

Do not interrupt or conduct during operation apt Upgrading is safer .

A few things to remember ：

If it is interrupted for some reason , Do you have a good backup to restore ？

Whether you send the log to another remote system ？

Is there any manually compiled software ？

Generalization

apt update The command is used to synchronize the list of packages on the system . It is for PPA And the repository to get the latest package list , And make sure they are up to date .

apt upgrade Command to upgrade the software package to the latest version , And install new packages when they are needed as dependencies . It will not delete any packages , If you specify to delete any packages , It will skip them .