symbolic link

A file whose contents are a path. Open it and the kernel follows the path; ask a tool about it and you may get an answer about the link instead of the target. That gap is where the time goes. On Ubuntu 24.04 /bin is a symbolic link to /usr/bin, so dpkg -S /bin/ls answers no path found matching pattern /bin/ls: coreutils recorded /usr/bin/ls, and dpkg compares the text you typed, not the file it leads to. readlink -f /bin/ls gives you the path dpkg knows. Other tools refuse outright — sudoedit /etc/resolv.conf answers editing symbolic links is not permitted, because the target could be swapped between the check and the write. Two paths reach the same bytes without being interchangeable arguments.