The lost+found folder is a part of Linux, macOS, and other UNIX-like operating systems. Each file system—that is, each partition—has its own lost+found directory. You’ll find recovered bits of corrupted files here.
On Linux, the fsck command—short for “file system check”—examines your file systems for errors. fsck may find bits of “orphaned” or corrupted files in the file system. If it does, fsck removes those corrupted bits of data from the file system and places them in the lost+found folder.
For example, if you abruptly shut your computer down while it’s running and files are being written to the hard drive, the fsck tool may automatically examine your file system the next time you boot your computer. If it finds any corrupted data, it places it in the file system’s lost+found folder.
This works similarly on macOS. If you run Disk Utility and check your disk for file system problems, it may find corrupted bits of data and store them in the lost+found folder.
Most UNIX file systems have a lost+found folder, including ext2, ext3, and ext4 on Linux, as well as the HFS+ file system on macOS. Some file systems may not use a lost+found folder, but they are less common on these operating systems.
Each file system has its own lost+found folder, so you’ll find one on each hard drive or partition. That means you’ll find a lost+found folder in the root directory at /lost+found, for example.
If you have other partitions mounted, you’ll find a lost+found folder on each of them as well. For example, if you have a separate partition for your home directory mounted at /home, you’ll find a lost+found folder at /home/lost+found. Orphaned data from the home partition will be placed in /home/lost+found instead of /lost+found.
If you have a USB drive or another external drive formatted with a Linux file system, you’ll also see a lost+found directory on it.
This folder is often hidden, so you may have to show hidden files and folders to see it.
This folder is generally restricted to the root user, preventing normal users from peeking inside and accessing recovered data they may normally not have permission to access. Don’t assume you have corrupted files lying around just because you see a lost+found folder—on many systems, it may be empty.
To see what’s inside, open a Terminal window and run the following commands in succession:sudo sucd /lost+foundls
(If the first command doesn’t work, try running su instead of sudo su —every Linux distro is a bit different.)
The terminal will list any files in the lost+found folder. If it doesn’t return anything, the folder is empty.
If something is in the lost+found folder, it usually won’t be entire files. Instead, you’ll see small pieces of files or bits of corrupted data, and you can’t do much with them.
If you haven’t lost any important data, you probably don’t need to worry about whatever is in the lost+found folder. If you did lose data, you can examine the lost+found folder and attempt to recover some of it. If you find a complete file in here, you can attempt to move the file back to its original location and use it. But there’s a slim chance you can do anything with the corrupted partial files. The fsck command put them there just in case.
You can’t delete the lost+found folder either, since it’s a permanent part of the file system. However, if you find useless file fragments inside the lost+found folder that you can’t piece back together, you can delete them using the terminal to free up space.