1FUSER(1) User Commands FUSER(1)
2
6 fuser - identify processes using files or sockets
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9 fuser [-fuv] [-a|-s] [-4|-6] [-c|-m|-n space] [ -k [-i] [-M] [-w]
10 [-SIGNAL] ] name ...
11 fuser -l
12 fuser -V
13
15 fuser displays the PIDs of processes using the specified files or file
16 systems. In the default display mode, each file name is followed by a
17 letter denoting the type of access:
18 c current directory.
20 e executable being run.
21 f open file. f is omitted in default display mode.
22 F open file for writing. F is omitted in default display
23 mode.
24 r root directory.
25 m mmap'ed file or shared library.
26 . Placeholder, omitted in default display mode.
27 fuser returns a non-zero return code if none of the specified files is
29 accessed or in case of a fatal error. If at least one access has been
30 found, fuser returns zero.
31 In order to look up processes using TCP and UDP sockets, the corre‐
33 sponding name space has to be selected with the -n option. By default
34 fuser will look in both IPv6 and IPv4 sockets. To change the default
35 behavior, use the -4 and -6 options. The socket(s) can be specified by
36 the local and remote port, and the remote address. All fields are op‐
37 tional, but commas in front of missing fields must be present:
38 [lcl_port][,[rmt_host][,[rmt_port]]]
40 Either symbolic or numeric values can be used for IP addresses and port
42 numbers.
43 fuser outputs only the PIDs to stdout, everything else is sent to
45 stderr.
46
48 -a, --all
49 Show all files specified on the command line. By default, only
50 files that are accessed by at least one process are shown.
51 -c Same as -m option, used for POSIX compatibility.
53 -f Silently ignored, used for POSIX compatibility.
55 -k, --kill
57 Kill processes accessing the file. Unless changed with -SIGNAL,
58 SIGKILL is sent. An fuser process never kills itself, but may
59 kill other fuser processes. The effective user ID of the
60 process executing fuser is set to its real user ID before at‐
61 tempting to kill.
62 -i, --interactive
64 Ask the user for confirmation before killing a process. This
65 option is silently ignored if -k is not present too.
66 -I, --inode
68 For the name space file let all comparisons be based on the in‐
69 odes of the specified file(s) and never on the file names even
70 on network based file systems.
71 -l, --list-signals
73 List all known signal names.
74 -m NAME, --mount NAME
76 NAME specifies a file on a mounted file system or a block device
77 that is mounted. All processes accessing files on that file
78 system are listed. If a directory is specified, it is automati‐
79 cally changed to NAME/ to use any file system that might be
80 mounted on that directory.
81 -M, --ismountpoint
83 Request will be fulfilled only if NAME specifies a mountpoint.
84 This is an invaluable seat belt which prevents you from killing
85 the machine if NAME happens to not be a filesystem.
86 -w Kill only processes which have write access. This option is
88 silently ignored if -k is not present too.
89 -n NAMESPACE, --namespace NAMESPACE
91 Select a different name space. The name spaces file (file
92 names, the default), udp (local UDP ports), and tcp (local TCP
93 ports) are supported. For ports, either the port number or the
94 symbolic name can be specified. If there is no ambiguity, the
95 shortcut notation name/space (e.g., 80/tcp) can be used.
96 -s, --silent
98 Silent operation. -u and -v are ignored in this mode. -a must
99 not be used with -s.
100 -SIGNAL
102 Use the specified signal instead of SIGKILL when killing pro‐
103 cesses. Signals can be specified either by name (e.g., -HUP) or
104 by number (e.g., -1). This option is silently ignored if the -k
105 option is not used.
106 -u, --user
108 Append the user name of the process owner to each PID.
109 -v, --verbose
111 Verbose mode. Processes are shown in a ps-like style. The
112 fields PID, USER and COMMAND are similar to ps. ACCESS shows
113 how the process accesses the file. Verbose mode will also show
114 when a particular file is being accessed as a mount point, knfs
115 export or swap file. In this case kernel is shown instead of
116 the PID.
117 -V, --version
119 Display version information.
120 -4, --ipv4
122 Search only for IPv4 sockets. This option must not be used with
123 the -6 option and only has an effect with the tcp and udp name‐
124 spaces.
125 -6, --ipv6
127 Search only for IPv6 sockets. This option must not be used with
128 the -4 option and only has an effect with the tcp and udp name‐
129 spaces.
130
132 /proc location of the proc file system
133
135 fuser -km /home
136 kills all processes accessing the file system /home in any way.
137 if fuser -s /dev/ttyS1; then :; else command; fi
139 invokes command if no other process is using /dev/ttyS1.
140 fuser telnet/tcp
142 shows all processes at the (local) TELNET port.
143
145 Processes accessing the same file or file system several times in the
146 same way are only shown once.
147 If the same object is specified several times on the command line, some
149 of those entries may be ignored.
150 fuser may only be able to gather partial information unless run with
152 privileges. As a consequence, files opened by processes belonging to
153 other users may not be listed and executables may be classified as
154 mapped only.
155 fuser cannot report on any processes that it doesn't have permission to
157 look at the file descriptor table for. The most common time this prob‐
158 lem occurs is when looking for TCP or UDP sockets when running fuser as
159 a non-root user. In this case fuser will report no access.
160 Installing fuser SUID root will avoid problems associated with partial
162 information, but may be undesirable for security and privacy reasons.
163 udp and tcp name spaces, and UNIX domain sockets can't be searched with
165 kernels older than 1.3.78.
166 Accesses by the kernel are only shown with the -v option.
168 The -k option only works on processes. If the user is the kernel,
170 fuser will print an advice, but take no action beyond that.
171 fuser will not see block devices mounted by processes in a different
173 mount namespace. This is due to the device ID shown in the process'
174 file descriptor table being from the process namespace, not fuser's;
175 meaning it won't match.
176
178 fuser -m /dev/sgX will show (or kill with the -k flag) all processes,
179 even if you don't have that device configured. There may be other de‐
180 vices it does this for too.
181 The mount -m option will match any file within the same device as the
183 specified file, use the -M option as well if you mean to specify only
184 the mount point.
185
187 kill(1), killall(1), lsof(8), mount_namespaces(7), pkill(1), ps(1),
188 kill(2).
189psmisc 2022-11-02 FUSER(1)