基础篇:df、du、磁盘分区、df命令

Linux学习

一、df命令
二、du命令
三、磁盘分区

一、df命令

1、需要关注的是磁盘的百分比；

[root@centos01 ~]# df
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda3       27043944 1182128  25861816   5% /
devtmpfs          923844       0    923844   0% /dev
tmpfs             933644       0    933644   0% /dev/shm
tmpfs             933644    8776    924868   1% /run
tmpfs             933644       0    933644   0% /sys/fs/cgroup
/dev/sda1         201380  111400     89980  56% /boot
tmpfs             186732       0    186732   0% /run/user/0
[root@centos01 ~]# 

2、df -h参数可以根据磁盘大小以适当的单位显示；tmpfs临时文件、devtmpfs是内存、需要关注的是dev开头的。

[root@centos01 ~]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        26G  1.2G   25G   5% /
devtmpfs        903M     0  903M   0% /dev
tmpfs           912M     0  912M   0% /dev/shm
tmpfs           912M  8.6M  904M   1% /run
tmpfs           912M     0  912M   0% /sys/fs/cgroup
/dev/sda1       197M  109M   88M  56% /boot
tmpfs           183M     0  183M   0% /run/user/0
[root@centos01 ~]# 

3、free命令

[root@centos01 ~]# free
          total        used        free      shared  buff/cache   available
Mem:        1867292      119412     1586324        8780      161556     1570544
Swap:       4194300           0     4194300
[root@centos01 ~]# 

4、df -i参数查看inode及inode数量使用状况；df -m以M为单位显示。

[root@centos01 ~]# df -m
Filesystem     1M-blocks  Used Available Use% Mounted on
/dev/sda3          26411  1155     25256   5% /
devtmpfs             903     0       903   0% /dev
tmpfs                912     0       912   0% /dev/shm
tmpfs                912     9       904   1% /run
tmpfs                912     0       912   0% /sys/fs/cgroup
/dev/sda1            197   109        88  56% /boot
tmpfs                183     0       183   0% /run/user/0
[root@centos01 ~]# df -k
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda3       27043944 1182124  25861820   5% /
devtmpfs          923844       0    923844   0% /dev
tmpfs             933644       0    933644   0% /dev/shm
tmpfs             933644    8776    924868   1% /run
tmpfs             933644       0    933644   0% /sys/fs/cgroup
/dev/sda1         201380  111400     89980  56% /boot
tmpfs             186732       0    186732   0% /run/user/0
[root@centos01 ~]# 

二、du命令

1、du用来查看一个文件大小的命令、du -sh /root/查看/root/目录的大小。

[root@centos01 ~]# du
16  ./.ssh
48  .
[root@centos01 ~]# du -sh /root/
48K /root/
[root@centos01 ~]# 

2、一个块只能有一个文件，小于4k默认以一个块为准。

[root@centos01 ~]# du
16  ./.ssh
0   ./1
0   ./2
0   ./3
0   ./4
0   ./5
0   ./6
48  .
[root@centos01 ~]# 
[root@centos01 ~]# du /root
16  /root/.ssh
0   /root/1
0   /root/2
0   /root/3
0   /root/4
0   /root/5
0   /root/6
48  /root
[root@centos01 ~]# 

三、磁盘分区

1、虚拟机设置添加磁盘；真实环境下服务器支持热插拔fdisk -l查看磁盘信息，此处没有新加磁盘信息，需重启虚拟机。

image.png

2、fdisk命令,重启后fdisk -l，新的磁盘出现。fdisk /dev/sdb然后m获取帮助。参数：n 创建新的分区；p列出分区；w保存并退出；d删除分区。普通磁盘分区格式为mbr最大支持2T，主分区最多只能划分4个；公式：主分区+扩展分区<=4;创建分区：n。在m帮助的处输入d，删除分区。

[root@centos01 ~]# fdisk -l

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/sda: 32.2 GB, 32212254720 bytes, 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000b196f

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      411647      204800   83  Linux
/dev/sda2          411648     8800255     4194304   82  Linux swap / Solaris
/dev/sda3         8800256    62914559    27057152   83  Linux
[root@centos01 ~]# 

[root@centos01 ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0xfaf07dfa.

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   g   create a new empty GPT partition table
   G   create an IRIX (SGI) partition table
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): 

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-41943039, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): 
Using default value 41943039
Partition 1 of type Linux and of size 20 GiB is set

Command (m for help):

3、先创建扩展分区，再次创建主分区时会提示创建主分区还是逻辑分区

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): e
Partition number (1-4, default 1): 
First sector (2048-41943039, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): 
Using default value 41943039
Partition 1 of type Extended and of size 20 GiB is set

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xfaf07dfa

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    41943039    20970496    5  Extended
Command (m for help): n
Partition type:
   p   primary (0 primary, 1 extended, 3 free)
   l   logical (numbered from 5)
Select (default p):

逻辑分区是从5开始的并且分区号是连续的；扩展分区或者主分区的分区号可以不连续；扩展分区只是个壳，不支持格式化，生效的是逻辑分区