用ls -l 可以看到有一个文档的硬链接数：
[root@localhost tmp]# ls -li
total 104
229415 drwxr-xr-x 2 root root 4096 Dec 11 21:15 etc
39757 -rw-r--r-- 2 root root 1602 Oct 30 14:56 hl_passwd
用一下语句可以查看一个文件有哪些硬链接
[root@localhost tmp]# find / -inum 39757
find: /proc/6266/task/6266/fd/4: No such file or directory
/etc/passwd
/tmp/hl_passwd
但是注意由于硬链接是不能跨文件系统的，所以
Add the `-xdev' option if you are starting the
search at a directory that has other filesystems mounted on it,
