the file osinstall.mpkg missing after updating this morning I ended up with the message on the screen that the osinstall.mpkg was missing, using Time Machine I managed to get everything back to normal without too much struggle, but what do I do now ? If I update is going to show the same mistake again ? How do I proceed ? Thanks
When you install from an "install application" on a primary-path disk, it guts the "install application" into an empty shell.

Copy the "install application" to an external drive.  When installed from there it does not end up gutted, or just use the external drive as a reusable copy.