In which file of the Linux system is information about the version and characteristics of the installed operating system stored by default?

Information about the version and characteristics of the installed Linux operating system by default is stored in the /etc/os-release file.

This file contains environment variables with data such as the distribution name, version, identifier, and other parameters.

Example content of /etc/os-release:

NAME="Ubuntu"
VERSION="20.04.6 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.6 LTS"
VERSION_ID="20.04"

To obtain information, you can use the command:

cat /etc/os-release

or

source /etc/os-release
echo $PRETTY_NAME

This file is the standard way to determine the OS version in most modern Linux distributions.