One problem with traditional package management is with maintainer script failures, which then leave the packaging system in a broken state. As the bug database shows, this is not uncommon.
> 'Read-only' is also redundant, as everything owned by root is basically read only.
Much of the core system runs as root, though, and can change system state that you then have to manage (with backups, careful handling of this state during upgrades, etc).
I back up / on the systems that I really care about. This is why. If / is read-only and only comes from an image, then I don't have to; I only need to make sure I have my image, and back up the parts of the filesystem that can change, which is far more limited.
> 'Read-only' is also redundant, as everything owned by root is basically read only.
Much of the core system runs as root, though, and can change system state that you then have to manage (with backups, careful handling of this state during upgrades, etc).
I back up / on the systems that I really care about. This is why. If / is read-only and only comes from an image, then I don't have to; I only need to make sure I have my image, and back up the parts of the filesystem that can change, which is far more limited.