is the a tool for Ubuntu, either bootable from an external USB or in-OS, that would allow creating full-partition backup of the system, and restore it if needed to bring the system and all the files in exact same state.
Ideally I'd like it to be in-OS, or if bootable it should back up to the same USB as itself (the install in question is very small). For reference, I am using Paragon Backup and Recovery on Windows for smth similar, it supports both bootable and in OS (using shadow copy) mode.
You can use Timeshift
I am sharing solution from this post:`
To briefly answer the question... it's because Timeshift is the work of a individual software developer.
Note: As of 19.04, it is in the repos now.
For those who don't know what Timeshift is...
The closest thing to a Windows-like restore point is by using Timeshift. I use it to save snapshots to an external USB hard drive. Although it can, it's normally not used for backing up your /home directory, just system-level changes. Use Backups (Déjà Dup) for backing up /home files.
Timeshift is a system restore utility which takes snapshots
of the system at regular intervals. These snapshots can be restored
at a later date to undo system changes. Creates incremental snapshots
using rsync or BTRFS snapshots using BTRFS tools.
More information at https://github.com/teejee2008/timeshift
For pre-19.04 add the PPA:
sudo add-apt-repository -y ppa:teejee2008/ppa
And install it:
sudo apt update
sudo apt install timeshift
How to use: Follow instructions in Timeshift GUI
You can use Redo Backup for a full partition backup. It can be installed on a bootable CD or on a USB drive. To use it, you boot from the CD or USB and then pick the drives and/or partitions you want to back up. The same tool allows you to restore from your backups. Here is where you can get it for free: https://sourceforge.net/projects/redobackup/ I have used Redo to backup and restore my Windows laptop as well as my Ubuntu desktop systems. I also use deja dup for scheduled backups of my data directories on a daily basis (e.g.: /home.) I like to take a backup of my entire system drive monthly just in case the hard drive fails so I can restore it to a new hard drive without going through an installation process.