I've been looking further into Linux from Scratch, and I am particularly interested in the package management side of the system. I understand that this is not covered in the book, but if I were to attempt LFS, package management would be a major convenience.
From what I have read, when upgrading packages like glibc, you have to recompile everything to reflect the change.
If that is true, how do package managers like pacman and apt get around this issue? Isn't lacking glibc for even the time it takes to replace the files catastrophic to the system?