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       fuser - identify processes using files or sockets


       fuser [-fuv] [-a|-s] [-4|-6] [-c|-m|-n  space ] [-k [-i] [-M] [-SIGNAL
       ] ] 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.

              F      open file for writing. F is omitted  in  default  display

              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
       corresponding 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, behavior, 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


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

       fuser outputs only the PIDs to  stdout,  everything  else  is  sent  to


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

       -c     Same as -m option, used for POSIX compatibility.

       -f     Silently ignored, used for POSIX compatibility.

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

       -l, --list-signals
              List all known signal names.

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

       -M --ismountpoint
              Request  will  be fulfilled only if NAME specifies a mountpoint.
              This is an invaluable seatbelt which prevents you  from  killing
              the machine if NAME happens to not be a filesystem.

       -n SPACE, --namespace 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 symbolic
              name can be specified. If there is no  ambiguity,  the  shortcut
              notation name/Ispace (e.g. 80/tcp ) can be used.

       -s, --silent
              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
              processes.  Signals  can be specified either by name (e.g. -HUP)
              or by number (e.g. -1). This option is silently ignored  if  the
              -k option is not used.

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

       -v, --verbose
              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. Verbose mode will also show when a
              particular file is being access as a mount point, knfs export or
              swap file. In this case kernel is shown instead of the PID.

       -V, --version
              Display version information.

       -4, --ipv4
              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

       -6, --ipv6
              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

       -      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.


       fuser -m /dev/sgX will show (or kill with the -k flag)  all  processes,
       even  if  you  don’t  have  that  device configured. There may be other
       devices it does this for too.

       fuser cannot report on any processes that it doesn’t have permission to
       look  at  the  file  descriptor  table  for.  The most common time this
       problem occurs is when looking for TCP  or  UDP  sockets  when  running
       fuser as a non-root user. In this case fuser will report no access

       The  mount  -m option will match any file within the save device as the
       specified file, use the -M option as well if you mean to  specify  only
       the mount point.


       Werner Almesberger <>

       Craig Small <>


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