FUSER(1)			 User Commands			      FUSER(1)

NAME
       fuser - identify processes using files or sockets

SYNOPSIS
       fuser [-fuv] [-a|-s] [-4|-6] [-c|-m|-n space] [ -k [-i] [-M] [-w]
       [-SIGNAL] ] name ...
       fuser -l
       fuser -V

DESCRIPTION
       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
		     mode.
	      r	     root directory.
	      m	     mmap'ed file or shared library.
	      .	     Placeholder, omitted in default display mode.

       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
       present:

       [lcl_port][,[rmt_host][,[rmt_port]]]

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

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

OPTIONS
       -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 kill.

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

       -I, --inode
	      For the name space file let all comparisons be based on the
	      inodes of the specified file(s) and never on the file names even
	      on network based file systems.

       -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 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 seat belt which prevents you from killing
	      the machine if NAME happens to not be a filesystem.

       -w     Kill only processes which have write access.  This option is
	      silently ignored if -k is not present too.

       -n NAMESPACE, --namespace NAMESPACE
	      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/space (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.

       -SIGNAL
	      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 accessed 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
	      namespaces.

       -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
	      namespaces.

FILES
       /proc  location of the proc file system

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

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

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

RESTRICTIONS
       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.

       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.

       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.

       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 will not see block devices mounted by processes in a different
       mount namespace.	 This is due to the device ID shown in the process'
       file descriptor table being from the process namespace, not fuser's;
       meaning it won't match.

BUGS
       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.

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

       fuser will not match mapped files, such as a process' shared libraries
       if they are on a btrfs(5) filesystem due to the device IDs being
       different for stat(2) and /proc/<PID>/maps.

SEE ALSO
       kill(1), killall(1), stat(2), btrfs(5), lsof(8), mount_namespaces(7),
       pkill(1), ps(1), kill(2).

psmisc				  2022-11-02			      FUSER(1)