vi, vim

vi is a very strong command line edit software.
vim was the advanced version of vi, adding the support of GUI.
Except vim, emacs is even stronger than vim.

vim + path to use vim

three modes of vi

• command mode
  default
  i : insert text at the cursor
  o : insert a new line below the current one
  dd : delete the whole row
  yy : put the current row's content to the ram(copy the current line)
  n+yy: put n rows' content to the ram(copy n lines)
  p : paste
  u : revoke the last manipulation
  r : replace current character
  / : find key word

• insert mode
  i
  Esc : back to the command mode

• ex mode
  :

:w     #save
: q    #quit
:q!    #force to quit
:set number    #show the line number
:! system command # execute a system command
:sh #return to the command line  and 'ctrl + d' can return to the vim 

Basic concept of disc

轉速越快，磁碟效能越強。但是，功率發熱量都會高。
SATA

• 柱面(cylinder)
  立體，多碟片疊加的柱面圈
• 扇區(sector)
  中心擴散出來的扇形
• 磁頭(head)
  讀寫資料，每個磁碟上下都有個磁頭

磁碟在linux中的表示

裝置名稱一般為hd[a-z]或sd[a-z]，如hda,hdb,sda,sdb
IDE裝置的名稱為hd[a-z],SATA,SCSI,SAS,USB等裝置名稱為sd[a-z]

concept of partition

將一個磁碟邏輯的分為幾個區，每個區當作獨立磁碟，以方便管理。
不同分割槽用： 裝置名稱 + 分割槽號 ，如sda1,sda2
主流的分割槽機制分為MBR和GPT兩種。

MBR

Master Boot Record. Traditional one. Applied to most BIOS PC device.

• support 32bit and 64bit
• there is a limit for partition
• support no more than 2T hard disk.

MBR partition

• main partition
  at most 4
• extended partition
  take a place of the main partition.
  can't be used. still need logical partition.
• logical partition
  can only be created by creating an extended partition first.
  Linux can support at most 63 IDE partition and 15 SCSI partition.

GPT

A new one.

• support more than 2T
• compatible with MBR
• only can be used on the hardware that supports UEFI
• only 64bit
• Mac,Linux both support GPT
• Windows 7 64bit, windowsServer2008(win10,win8?)