FUSER(1)                         User Commands                        FUSER(1)

       fuser - identify processes using files or sockets

       fuser [-a|-s] [-4|-6] [-n space] [-signal] [-kimuv] name ...
       fuser -l
       fuser -V

       fuser  displays the PIDs of processes using the specified files or file
       systems.  In the default display mode, each file name is followed by  a
       letter denoting the type of access:

              c      current directory.

              e      executable being run.

              f      open file. f is omitted in default display mode.

              r      root directory.

              m      mmap'ed file or shared library.

       fuser  returns a non-zero return code if none of the specified files is
       accessed or in case of a fatal error. If at least one access  has  been
       found, fuser returns zero.

       In  order  to  look  up processes using TCP and UDP sockets, the corre-
       sponding name space has to be selected with the -n option.  By  default
       fuser  will look in both IPv6 and IPv4 sockets.  To change the default,
       behavour, use the -4 and -6 options. The socket(s) can be specified  by
       the  local  and  remote  port,  and  the remote address. All fields are
       optional, but commas in front of missing fields must be present:


       Either symbolic or numeric values can be used for IP addresses and port

       -a     Show  all  files specified on the command line. By default, only
              files that are accessed by at least one process are shown.

       -k     Kill processes accessing the file. Unless changed with  -signal,
              SIGKILL  is  sent.  An fuser process never kills itself, but may
              kill other fuser processes. The effective user ID of the process
              executing  fuser is set to its real user ID before attempting to

       -i     Ask the user for confirmation before  killing  a  process.  This
              option is silently ignored if -k is not present too.

       -l     List all known signal names.

       -m     name specifies a file on a mounted file system or a block device
              that is mounted. All processes accessing files on that file sys-
              tem  are  listed.  If a directory file is specified, it is auto-
              matically changed to name/. to use any file system that might be
              mounted on that directory.

       -n space
              Select a different name space. The name spaces file (file names,
              the default), udp (local UDP ports), and tcp (local  TCP  ports)
              are  supported.   For  ports, either the port number or the sym-
              bolic name can be specified.  If  there  is  no  ambiguity,  the
              shortcut notation name/space (e.g. name/proto) can be used.

       -s     Silent  operation.  -u and -v are ignored in this mode.  -a must
              not be used with -s.

              Use the specified signal instead of SIGKILL  when  killing  pro-
              cesses.  Signals  can be specified either by name (e.g. -HUP) or
              by number (e.g. -1).

       -u     Append the user name of the process owner to each PID.

       -v     Verbose mode. Processes are shown in a ps-like style. The fields
              PID,  USER  and  COMMAND are similar to ps. ACCESS shows how the
              process accesses the file. If the access is by the kernel  (e.g.
              in  the  case  of  a  mount point, a swap file, etc.), kernel is
              shown instead of the PID.

       -V     Display version information.

       -4     Search only for IPv4 sockets.  This option must not be used with
              the -6 option and only has an effect with the tcp and udp names-

       -6     Search only for IPv6 sockets.  This option must not be used with
              the -4 option and only has an effect with the tcp and udp names-

       -      Reset all options and set the signal back to SIGKILL.

       /proc     location of the proc file system

       fuser -km /home kills all processes accessing the file system /home  in
       any way.

       if fuser -s /dev/ttyS1; then :; else something; fi invokes something if
       no other process is using /dev/ttyS1.

       fuser telnet/tcp shows all processes at the (local) TELNET port.

       Processes accessing the same file or file system several times  in  the
       same way are only shown once.

       If the same object is specified several times on the command line, some
       of those entries may be ignored.

       fuser may only be able to gather partial information  unless  run  with
       privileges.  As  a  consequence, files opened by processes belonging to
       other users may not be listed and  executables  may  be  classified  as
       mapped only.

       Installing  fuser SUID root will avoid problems associated with partial
       information, but may be undesirable for security and privacy reasons.

       udp and tcp name spaces, and UNIX domain sockets can't be searched with
       kernels older than 1.3.78.

       udp  and tcp currently  work with IPv6 and IPv4, but the address fields
       can only be IPv4 addresses.

       Accesses by the kernel are only shown with the -v option.

       The -k option only works on processes. If the user is the kernel, fuser
       will print an advice, but take no action beyond that.

       Werner Almesberger <>

       kill(1), killall(1), lsof(8), ps(1), kill(2)

Linux                          October 25, 1999                       FUSER(1)