well, since you seem to have deleted a file, this is what we are looking for
what file is it?
what app created it, is it a odf, a jpeg, a doc, a mp3?
open konsole, write su and then enter, write you root password and enter
then write photorec and enter
maximize the window of photorec, the smaller window of konsole is not enough for this app
once you are there, select the hard disk that contains the partition you used to store the file and press enter
on that list select intel/pc and enter
then a list of the logical partitions on that disk will be showed, press up or down arrow keys to select the partition that contained the file, if you have /home partition, select it, you can distinguish it for he size, here you won't see the name
if you don't have a /home partition, then select the / partition
in the lower section of the screen you can see 4 options
search, options, file opt and quit, by moving the left and right keys on the keyboard select file options and press enter
a long list of filetypes will be listed, press spacebar to select which ones you want to search or which ones doesn't
press up or down and when finished press enter, be sure to select the search option with the right partition selected
then it will ask the type of partition it is, it is probably a ext3 or ext4 so select that
the next question will be where to put the files that it will recover
ideally you shouldn't use the same partition you have the file you want to recover to store the files it will find on the search process, also you should have enough space, around 20 gbs, sometimes it finds too many things
press y once you have selected where the files will be stored, the process will start immediately and will show how many files and the type of the files, it will also show a estimated time to complete the task
when finished the task open the folder you selected to store the recovered files and see if it found the right file
if not verify that you selected the right type of files to search but don't let it search for every file, you will find too many files, 20000 or more, be very selective
good luck finding the file
