几乎只要建站用的VPS都以Linux居多，免费又好用。
虽不能把全部Liunx命令记住，但必要的命令还是要记下为好，今天介绍的命令是df磁盘空间占用情况查看命令
看看帮助文档:
[nicholas@qttc ~]$ df --help
Usage: df [OPTION]... [FILE]...
Show information about the file system on which each FILE resides,
or all file systems by default.
Mandatory arguments to long options are mandatory for short options too.
-a, --all include dummy file systems
-B, --block-size=SIZE use SIZE-byte blocks
--direct show statistics for a file instead of mount point
--total produce a grand total
-h, --human-readable print sizes in human readable format (e.g., 1K 234M 2G)
-H, --si likewise, but use powers of 1000 not 1024
-i, --inodes list inode information instead of block usage
-k like --block-size=1K
-l, --local limit listing to local file systems
--no-sync do not invoke sync before getting usage info (default)
-P, --portability use the POSIX output format
--sync invoke sync before getting usage info
-t, --type=TYPE limit listing to file systems of type TYPE
-T, --print-type print file system type
-x, --exclude-type=TYPE limit listing to file systems not of type TYPE
-v (ignored)
--help display this help and exit
--version output version information and exit
Display values are in units of the first available SIZE from --block-size,
and the DF_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environment variables.
Otherwise, units default to 1024 bytes (or 512 if POSIXLY_CORRECT is set).
SIZE may be (or may be an integer optionally followed by) one of following:
KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.
Report df bugs to bug-coreutils@gnu.org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
For complete documentation, run: info coreutils 'df invocation'
df命令可以检查文件系统的磁盘空间占用情况。可以利用该命令来获取硬盘被占用了多少空间，目前还剩下多少空间等信息
df [option]
Linux中df命令可显示所有文件系统对i节点和磁盘块的使用情况, 该命令各个选项的含义如下
-a 显示所有文件系统的磁盘使用情况，包括0块（block）的文件系统，如/proc文件系统 -k 以k字节为单位显示 -i 显示i节点信息，而不是磁盘块 -t 显示各指定类型的文件系统的磁盘空间使用情况 -x 列出不是某一指定类型文件系统的磁盘空间使用情况（与t选项相反） -T 显示文件系统类型
使用df -i
[nicholas@qttc ~]$ df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/xvda1 20480000 78530 20401470 1% /
tmpfs 127289 1 127288 1% /dev/shm
使用df -hl
[nicholas@qttc ~]$ df -hl
Filesystem Size Used Avail Use% Mounted on
/dev/xvda1 20G 12G 8.5G 57% /
tmpfs 498M 0 498M 0% /dev/shm
