In general, what are the reasons why a filetype might show as unknown (?) in ls output? See the first bit for the file /sbin/start-stop-daemon, which should indicate - for regular file, instead is displayed as ? for unknown. ts7500:~# ls -alh /sbin/s*-rwxr-xr-x 1 root  root  52K Apr 29  2008 /sbin/sfdisk-rwxr-xr-x 1 root  root  875 Dec  6  2009 /sbin/shadowconfig-rwxr-xr-x 1 root  root  12K Apr 19  2010 /sbin/showmount-rwxr-xr-x 1 root  root  18K Aug 12  2008 /sbin/shutdown-rwxr-xr-x 1 root  root  28K Nov 16  2008 /sbin/slattach-rwxr-xr-x 1 root  root  12K Apr 19  2010 /sbin/sm-notify-rwxr-xr-x 1 root  root  58K Jul 27  2008 /sbin/ss?rwsrwsrwt 1 65535 root 4.0G Dec 31  1969 /sbin/start-stop-daemon-rwxr-xr-x 1 root  root  19K Aug 12  2008 /sbin/startpar-rwxr-xr-x 1 root  root 9.8K Aug 12  2008 /sbin/suloginlrwxrwxrwx 1 root  root    6 Jun  9  2011 /sbin/swapoff -> swapon-rwxr-xr-x 1 root  root  17K Apr 29  2008 /sbin/swapon-rwxr-xr-x 1 root  root  11K Aug  6  2009 /sbin/sysctl
Unknown Filetype in ls
linux;files;ls;file types