On a Debian system, how is the 'installed-size' field of the control file used?

One of the fields included in the control file of a .deb package is the 'Installed-Size', which should inform of the final disk occupation (in kB) of the package in question.

My question is when/how is this information typically used?

Is it e.g. dpkg using it to inform and maybe prevent a user with low free disk space to install/upgrade a system? Has the information any value after an installation has completed?

Solution 1:

From the Debian Policy Manual:

5.6.20 Installed-Size

This field appears in the control files of binary packages, and in the Packages files. It gives an estimate of the total amount of disk space required to install the named package. Actual installed size may vary based on block size, file system properties, or actions taken by package maintainer scripts.

The disk space is given as the integer value of the estimated installed size in bytes, divided by 1024 and rounded up.

I suspect the intention is for this field to be used by package managers and the like to give the user an idea of how much disk space the installed package will take up.