I accidently remove a file with rm.

==When deleting, inode disconnected and release space.
==

#So I tried:
{

Df #check out which drive is root in


debugfs


Open [drive name,/dev/mapper/ubuntu--vg-root in my case]


lsdel

}

#I failed to found anything

#Try software extundelete.

I use sudo extundelete /dev/mapper/ubuntu--vg-root --restore-all because I have no time to read the manual.

#Use grep to find the correct file I want in dictionary RECOVERED_FILES.


#Success in my case.