[yz@localhost ~]$ lsof | less
COMMAND     PID   TID           USER   FD      TYPE             DEVICE  SIZE/OFF      NODE NAME
systemd       1                 root  cwd   unknown                                        /proc/1/cwd (readlink: Permission denied)
systemd       1                 root  rtd   unknown                                        /proc/1/root (readlink: Permission denied)
systemd       1                 root  txt   unknown                                        /proc/1/exe (readlink: Permission denied)
systemd       1                 root NOFD                                                  /proc/1/fd (opendir: Permission denied)
kthreadd      2                 root  cwd   unknown                                        /proc/2/cwd (readlink: Permission denied)
kthreadd      2                 root  rtd   unknown                                        /proc/2/root (readlink: Permission denied)