To simulate a Linux package upgrade without actually installing anything (i.e. a "dry run"), you can use the --simulate or -s option with the package management tool.
On a Debian-based system, such as Ubuntu, you can use the apt-get or apt command with the --simulate option to simulate an upgrade.
For example, to simulate an upgrade of all packages using apt-get, you can run the following command:
apt-get --simulate upgradeSourcewww:.lautturi.com
To simulate an upgrade of all packages using apt, you can run the following command:
apt --simulate upgrade
This will show a list of packages that would be upgraded if the upgrade were actually performed, along with the current version and the version that would be installed by the upgrade. It will also show the size of the package and the amount of disk space that would be required to install the update.
Keep in mind that the simulation does not take into account any dependencies or conflicts that may arise during an actual upgrade, so the results of the simulation may not be accurate.