- install bootmenu
- switch off
- if not already done, install an additional uSD card if you don't have it
- switch your device on with open keyboard
- select backupmenu
- select option B
- select option T (backup both OptFS and RootFS)
- wait
done, reboot

Next time you need to bring your device at that very specific point in time:
- switch it off
- switch it on
- select backupmenu
- and chose restore backup optioin

that's it.

I am currently on my 5th -scavenged and frankesteinezed- N900, never lost any single bit of my data tanks to very recent backups when the worst happened on me (two faulty digitizers, one usb port broken and one 'missing telephony' modem fault)