fuser(1) — Linux manual page


FUSER(1)                      User Commands                     FUSER(1)

NAME         top

       fuser - identify processes using files or sockets

SYNOPSIS         top

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

DESCRIPTION         top

       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:


       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

OPTIONS         top

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

       -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.

              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         top

       /proc  location of the proc file system

EXAMPLES         top

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

       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         top

       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

       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         top

       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         top

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

COLOPHON         top

       This page is part of the psmisc (Small utilities that use the
       /proc filesystem) project.  Information about the project can be
       found at ⟨https://gitlab.com/psmisc/psmisc⟩.  If you have a bug
       report for this manual page, see
       ⟨https://gitlab.com/psmisc/psmisc/issues⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨https://gitlab.com/psmisc/psmisc.git⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-11-14.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

psmisc                         2022-11-02                       FUSER(1)

Pages that refer to this page: killall(1)lsof(8)