Why is mv so much faster than cp? How to recover from an incorrect mv command

cpfile-copymv

I drag and drop a folder into another by mistake in FileZilla.

~/big_folder
~/some_other_folder

The folder got moved is a very huge one. It includes hundreds of thousands of files (node_modules, small image files, a lot of folders)

What is so weird is that after I release my mouse, the moving is done. The folder "big_folder" is moved into "some_other_folder".

~/some_other_folder/big_folder

(there is no big_folder in the ~/ after moving)

Then I realize the mistake and try move back but it fails both on FileZilla and terminal.

Then I have to cp -r to copy files back because there are server-side codes accessing those files in ~/big_folder

And it takes like forever to wait …

What should I do?

BTW, here are the output from FileZilla (it's the failure of the moving back):

Status:       Renaming '/root/big_folder' to '/root/some_other_folder/big_folder'
Status:       /root/big_folder -> /root/some_other_folder/big_folder

Status:       Renaming '/root/some_other_folder/big_folder' to '/root/big_folder'
Command:  mv "big_folder" "/root/big_folder"
Error:          mv /root/some_other_folder/big_folder /root/big_folder: received failure with description 'Failure'

Best Answer

If a directory is moved within the same filesystem (the same partition), then all that is needed is to rename the file path of the directory. No data apart from the directory entry for the directory itself has to be altered.

When copying directories, the data for each and every file needs to be duplicated. This involves reading all the source data and writing it at the destination.

Moving a directory between filesystems would involve copying the data to the destination and removing it from the source. This would take about as long time as copying (duplicating) the data within a single filesystem.

If FileZilla successfully renamed the directory from ~/big_folder to ~/some_other_folder/big_folder, then I would revert that using

mv ~/some_other_folder/big_folder ~/big_folder

... after first making sure that there were no directory called ~/big_folder (if there was, the move would put big_folder from some_other_folder into the ~/big_folder directory as a subfolder).

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