John Lightsey on rm -r

• Security expert with cPanel in Houston

• The rm command doesn't attempt to modify permissions on anything, so to do a recursive deletion (rm -r), it needs:

  • write permissions on the directory inodes it is modifying to remove directory entries.

    • An "inode is a data structure in a Unix-style file system that describes a filesystem object such as a file or a directory."

      • https://en.wikipedia.org/wiki/Inode, last edited July 26 2017, retrieved August 2 2017.

  • execute permissions on any directories it needs to traverse across to access subdirectories.

  • read permissions on any directories it needs to traverse across so that it can see that it needs to traverse.

• Hence, with:

  • rw (0600)

    • You can't traverse to remove subdirectories or files in the directory. You can see that the directory contents are there but can't stat() them.

  • rx (0500)

    • You can't alter the directory to remove its contents (though you can see the contents).

  • wx (0300)

    • You can't see what the directory contains (so if it contains anything and rmdir() fails, there is no way to recurse downwards.)