20180925 df與du命令、fdisk磁盤分區

df 命令

disk filesystem的縮寫,查看已掛載磁盤的總容量、使用容量、剩餘容量信息。

[root@centos01 ~]# df
Filesystem     1K-blocks   Used Available Use% Mounted on
/dev/sda3       27043944 885972  26157972   4% /
devtmpfs          499848      0    499848   0% /dev
tmpfs             505428      0    505428   0% /dev/shm
tmpfs             505428   6792    498636   2% /run
tmpfs             505428      0    505428   0% /sys/fs/cgroup
/dev/sda1         201388  76016    125372  38% /boot

帶tmpfs說明該文件系統是臨時文件系統
/dev/shm爲內存分區，默認大小爲物理內存的一半
free 命令能夠查看swap分區

[root@centos01 ~]# free
             total       used       free     shared    buffers     cached
Mem:       1010860     231640     779220       6796        692      81600
-/+ buffers/cache:     149348     861512
Swap:      4194300          0    4194300

-h: 表示使用合適的單位顯示容量信息

[root@centos01 ~]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        26G  866M   25G   4% /
devtmpfs        489M     0  489M   0% /dev
tmpfs           494M     0  494M   0% /dev/shm
tmpfs           494M  6.7M  487M   2% /run
tmpfs           494M     0  494M   0% /sys/fs/cgroup
/dev/sda1       197M   75M  123M  38% /boot

-k、-m：分別表示以KB和MB單位顯示磁盤容量信息

-i: 查看磁盤inodes使用狀況，若已使用100%，即便有剩餘的磁盤空間，也會提示磁盤已滿。
inodes大小是在磁盤格式化時肯定的，是根據磁盤分區決定其大小。

du 命令

disk useage. 用來查看一個文件或目錄所佔的空間大小。
當一個文件小於4k時，也會顯示爲4k。由於磁盤會劃分爲多個小塊，文件都存到這些小塊裏，不夠4k時，也佔用着這個4k的塊，每一個小塊只能有一個文件。
-s 只列出總和大小。
-h 表示使用合適的單位顯示容量信息。
通常使用： du -sh 目錄/文件

磁盤管理

fdisk -l 列出系統全部的磁盤
虛擬機添加磁盤後須要重啓系統(reboot)


默認選擇硬盤後，一直「下一步」

到這裏，單擊「完成」磁盤添加完成

經過上面操做重啓後系統後

[root@centos01 ~]# fdisk -l

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: 0x000b933a

   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

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 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/sdb爲新磁盤，尚未進行分區

[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 0xbe968c4c.

Command (m for help): p   # 打印當前磁盤的分區信息

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 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: 0xbe968c4c

   Device Boot      Start         End      Blocks   Id  System

Command (m for help): n  # 分區
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p  # 選擇主分區
Partition number (1-4, default 1): 1 # 分區號
First sector (2048-10485759, default 2048): 2048 # 開始的扇區
Last sector, +sectors or +size{K,M,G} (2048-10485759, default 10485759): +2G  # 大小
Partition 1 of type Linux and of size 2 GiB is set

Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p): e  # 擴展分區
Partition number (2-4, default 2): 2
First sector (4196352-10485759, default 4196352):
Using default value 4196352
Last sector, +sectors or +size{K,M,G} (4196352-10485759, default 10485759): +1G
Partition 2 of type Extended and of size 1 GiB is set

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 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: 0xbe968c4c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   83  Linux
/dev/sdb2         4196352     6293503     1048576    5  Extended

Command (m for help): n
Partition type:
   p   primary (1 primary, 1 extended, 2 free)
   l   logical (numbered from 5)
Select (default p): p
Partition number (3,4, default 3): 3
First sector (6293504-10485759, default 6293504):
Using default value 6293504
Last sector, +sectors or +size{K,M,G} (6293504-10485759, default 10485759): +2G
Value out of range.
Last sector, +sectors or +size{K,M,G} (6293504-10485759, default 10485759):
Using default value 10485759
Partition 3 of type Linux and of size 2 GiB is set

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 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: 0xbe968c4c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   83  Linux
/dev/sdb2         4196352     6293503     1048576    5  Extended
/dev/sdb3         6293504    10485759     2096128   83  Linux

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 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: 0xbe968c4c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   83  Linux
/dev/sdb2         4196352     6293503     1048576    5  Extended
/dev/sdb3         6293504    10485759     2096128   83  Linux

Command (m for help): d # 刪除分區
Partition number (1-3, default 3): 2 #刪除的分區號
Partition 2 is deleted

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes, 10485760 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: 0xbe968c4c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     4196351     2097152   83  Linux
/dev/sdb3         6293504    10485759     2096128   83  Linux

邏輯分區是從第5個分區號開始，而且是連續的。
擴展分區能夠劃分爲必定大小的空間，但真正佔用空間的是擴展分區裏的邏輯分區；擴展分區自己不支持格式化，寫數據，是一個裝着邏輯分區的「殼」。
主分區數量範圍1 ~ 3，邏輯分區數量範圍0 ~ 1。