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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

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fuser [options] [files | filesystems]

Identifies and outputs the process IDs of processes that are using the files or local filesystems. Each process ID is followed by a letter code: c if process is using file as the current directory; e if executable; f if an open file; m if a shared library; and r if the root directory. Any user with permission to read /dev/kmem and /dev/mem can use fuser, but only a privileged user can terminate another user's process. fuser does not work on remote (NFS) files.

If more than one group of files is specified, the options may be respecified for each additional group of files. A lone dash (-) cancels the options currently in force, and the new set of options applies to the next group of files. Like a number of other administrator commands, fuser is usually installed to the /sbin directory. You may need to add that directory to your path or execute the command as /sbin/fuser.



Return all options to defaults.


Send signal instead of SIGKILL.


Display information on all specified files, even if they are not being accessed by any processes.


Request user confirmation to kill a process. Ignored if -k is not also specified.


Send SIGKILL signal to each process.


List signal names.


Expect files to exist on a mounted filesystem; include all files accessing that filesystem.

-n space

Set the namespace checked for usage. Acceptable values are file for files, udp for local UPD ports, and tcp for local TCP ports.




User login name, in parentheses, also follows process ID.




Display version information.

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