fuser - identify processes using files or sockets


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

   -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.

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

   -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/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)orby 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.

   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.


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


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.