The sysadmin needs to get a list of packages for various reasons: reinstalling the system, installing packages on another machine, checking versions and compatibility, or others.
You can output packages with the command:
dpkg-query -l
A list will appear in the panel indicating the name, the current current version and a brief description of the purpose.
For Ubuntu , it is used:
sudo apt list --installed
It also displays a package listing indicating the current version and architecture. There are commands that allow you to display only a list of packages with names, but they are used less often).
As a rule, the system administrator needs to transfer the installed list of packages from one server to another, and not to install and/or configure each separately.
To do this, you need to perform 2 actions
save the list of packages from server #1 that were previously output by the command;
roll dependencies to server #2.
To create a file with a list of installed packages, use:
dpkg --get-selections | grep -v deinstall > allpackages.txt
Name "allpackages.txt " given for example. You can use any names: "alllists.txt ", "lists.txt ", "packages.txt "and so on.
The file with the list of packages and versions is copied to server No. 2 with your address. For example, for 200.200.200.200, the command will look like this:
scp allpackages.txt 200.200.200.200:~/
It remains only to roll the packages from the copied file. To do this, use the command:
$ sudo apt-get install -y $(< allpackages.txt)
Ready! Now you have moved the package list from server #1 to server #2.