fuser详解

fuser(1) – Linux man page
Name
fuser – identify processes using files or sockets
# 注释 ：fuser 找出使用指定文件或者 sockets 的进程
Synopsis
fuser [-a|-s|-c] [-4|-6] [-n space ] [-k [-i] [-signal ] ] [-muvf] 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:
# 注释 ：fuser 显示使用指定文件或者文件系统的进程的 pid ，默认会在每个 pid 后面加上一个字符表示访问的方式 ：
# -）1、c ：表示 current directory 。表示进程是在该目录下启动的。
# -）2、e ：表示是可执行的程序
# -）3、f ：打开文件。默认不显示
# -）4、r ：root 目录，表示该目录是该进程的 / 目录
# -）5、m ：表示 mmap 过的文件或者共享库
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.
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.
# 注释 ：如果指定文件没有任何进程访问，或者出现严重错误，fuser 返回非 0 的 exit status。
# 如果至少存在一个进程，则 fuser 返回 0
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:
# 注释：为了查找使用某个 TCP /UDP sockets 的进程，你必须用 -n 指定 （name space）tcp 还是 udp 。
# 默认 fuser 会查找 ipv4 和 ipv6 sockets 。你可以使用 -4 或者 -6 来改变选项
# sockets 可以按照 local port:remote_host:remote_port 的方式来指定。每个字段都是可选的，但不能省略 ‘,’
[lcl_port][,[rmt_host][,[rmt_port]]]
Either symbolic or numeric values can be used for IP addresses and port numbers.
# 注释 ；在端口方面，你可以用端口名或者数字表示
fuser outputs only the PIDs to stdout, everything else is sent to stderr.
# 注释 ：fuser 只输出 PID 到 stdout ，其他都送给 stderr
Options
-a
Show all files specified on the command line. By default, only files that are accessed by at least one process are shown.
# 注释 ：-a 显示所有指定文件的情况，即使没有进程访问它们。
-c
Same as -m option, used for POSIX compatibility.
-f
Silently ignored, used for POSIX compatibility.
-k
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.
# 注释 ：-k 表示杀死访问指定文件的进程。默认发送 SIGKILL （-9）信号。fuser 进程永远不会杀死自己。
# 但可能杀死其他 fuser 进程。在尝试杀死进程前，fuser 会改变 euid 为 ruid
-i
Ask the user for confirmation before killing a process. This option is silently ignored if -k is not present too.
# 注释 ：-i 表示交互模式，在杀死进程前会提示。必须和 -k 合用
-l
List all known signal names.
# 注释 ：-l 列出所有已知的信号
-m
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.
# 注释：-m 表示指定文件所在的文件系统或者块设备（处于 mount 状态）。所有访问该文件系统的进程都被列出。
# 假如指定了一个目录，则自动在后面加上 ‘/’ 表示该挂载在该目录上的文件系统
-n 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 shortc ut notation name/Ispace (e.g. 80/tcp ) can be used.
# 注释 ：-n 指定 sockets 的协议类型。可以是 file（默认）、udp、tcp 。
# 你甚至可以使用 ‘ / ‘ 的简写方式，只要不存在异义的话
-s
Silent operation. -u and -v are ignored in this mode. -a must not be used with -s.
# 注释 ：-s 表示安静模式。-u 和 -v 会被忽略，-a 不能和 -s 一起使用
-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.
# 注释：- 指定信号
-u
Append the user name of the process owner to each PID.
# 注释 ：-u 表示在 PID 后面加上进程的 owner
-v
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. If the access is by the kernel (e.g. in the case of a mount point, a swap file, etc.), kernel is shown instead of the PID.
# 注释 ：-v 表示 verbose 模式。进程以 ps 的方式显示，包括 PID、USER、COMMAND、ACCESS 字段
# 如果是内核访问的（例如 mount point、swap 文件），则显示为 kernel 而不是 pid
-V
Display version information.
-4
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
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.
-
Reset all options and set the signal back to SIGKILL.
# 注释：‘-’ 表示重置所有选项并把信号设置为 SIGKILL
Files
/proc location of the proc file system
Examples
fuser -km /home
kills all processes accessing the file system /home in any way.
# 注释 ：fuser -km /home 杀死所有访问 /home 文件系统的进程
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.
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.
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.
udp and tcp currently work with IPv6 and IPv4, but the address fields can only be IPv4 addresses.
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.
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.
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
Authors
Werner Almesberger
Craig Small
See Also
kill(1), killall(1), lsof(8), ps(1), kill(2).
REFERENCED BY
tmpwatch(8)