Similarly to this question about restarting ssh when ssh is the only mode of connection to a server, what happens if I
aptitude upgrade screen inside a screen session?
The upgrades are designed to be compatible between minor versions. The Linux upgrades are usually with only the minor version changes. So if you upgrade a library all programs using it will remain compatible with that library (API will be compatible). Same is for the configuration files. When the upgrade is running, the files are replaced. The files that are opened (like screen) will keep the inode on the disk and the the application the has opened it before upgrade will use the old version of the file. All new instances of the program will use the new version. When the application is closed, the file descriptor will be closed and the inode will be deleted releasing the disk space.
What is interesting is that you can have the 2 versions of the same application running at the same time. Some of the post install script of the packages are restarting the daemons so that the new instance will run the new version of the service. The reason we have major versions for the distributions and major versions of the programs is to delimit the API/ABI/configuration, etc. incompatibilities.
screen will continue running.
i know that, cos i do that ;)
after you finish screen session and start new , only then you have new screen