linux查看文件被哪个进程占用？

1> 如果文件是端口号

netstat -ntlp | grep portNum

[root@localhost root]# netstat -ntlp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp               0.0.0.0:           0.0.0.0:*               LISTEN      -
tcp               0.0.0.0:            0.0.0.0:*               LISTEN      -
tcp               0.0.0.0:           0.0.0.0:*               LISTEN      -
tcp               0.0.0.0:            0.0.0.0:*               LISTEN      /gmond
tcp               0.0.0.0:            0.0.0.0:*               LISTEN      /svnserve
tcp               0.0.0.0:             0.0.0.0:*               LISTEN      /rpcbind
tcp               0.0.0.0:           0.0.0.0:*               LISTEN      /rpc.mountd
tcp               0.0.0.0:              0.0.0.0:*               LISTEN      /rsync
tcp               0.0.0.0:              0.0.0.0:*               LISTEN      /sshd
tcp               127.0.0.1:           0.0.0.0:*               LISTEN      /cupsd
tcp               0.0.0.0:           0.0.0.0:*               LISTEN      /rpc.statd
tcp6              :::                 :::*                    LISTEN      -
tcp6              :::                :::*                    LISTEN      /rpc.statd
tcp6              :::                :::*                    LISTEN      -
tcp6              :::                  :::*                    LISTEN      /rpcbind
tcp6              :::                :::*                    LISTEN      /rpc.mountd
tcp6              :::                   :::*                    LISTEN      /httpd
tcp6              :::                :::*                    LISTEN      -
tcp6              :::                   :::*                    LISTEN      /rsync
tcp6              :::                   :::*                    LISTEN      /sshd
tcp6              :::                 :::*                    LISTEN      /cupsd 

2>如果是普通文件

lsof

fuser

3>如果是磁盘空间

du -sh : 查看当前目录总共占的容量。而不单独列出各子项占用的容量

du -lh --max-depth=1 : 查看当前目录下一级子文件和子目录占用的磁盘容量

4> 如何释放缓存

用sync命令可以把内存中的数据写入硬盘，同时还有/proc/sys/vm/drop_caches这个文件可以。

关于drop_caches文件：系统默认为0， 在Documentation/sysctl/vm.txt中有如下描述:

drop_caches

Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free.

To free pagecache:仅清除页面缓存（PageCache）
 echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:清除目录项和inode
 echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:清除页面缓存，目录项和inode
 echo 3 > /proc/sys/vm/drop_caches

As this is a non-destructive operation and dirty objects are not freeable, the user should run `sync' first.

一般来讲 echo 1 > /proc/sys/vm/drop_caches就好。