Ubuntu Manpage: fuser - identify processes using files or sockets

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.