1, Disk Foundation

1.1 disk structure

• Physical structure of hard disk
  • Disc: the hard disk has multiple discs, each disc has 2 sides
  • Magnetic head: one magnetic head on each side
• Data structure of hard disk
  • Sector: the disk is divided into multiple sector areas, and each sector stores five 12 bytes of data
  • Track: concentric circles with different radii on the same disk
  • Cylindrical surface: a cylindrical surface composed of different discs with the same radius
• Hard disk storage capacity = number of heads × Number of tracks (cylinders) × Sectors Per Trark × Bytes per sector
• Cylinder / head / sector can be used to uniquely locate each area on the disk
• Disk interface type
  • IDE, SATA, SCSI, SAS, fibre channel
• MBR and disk partition representation
  • Master Boot Record (MBR)
  • The MBR is located in the first physical sector of the hard disk
  • MBR contains the main boot program of the hard disk and the hard disk partition table
  • The partition table has four partition record areas, and each partition record area accounts for 16 bytes
• Linux represents hard disk, partition and other devices as files
  

1.2 disk partition structure

• The number of primary partitions in the hard disk is only 4
• The serial numbers of primary and extended partitions are limited to 1 ~ 4
• The extended partition is subdivided into logical partitions
• The logical partition sequence number will always start with 5
  

2, File system type

• XFS file system
  • Partition for storing file and directory data
  • High performance log file system
  • File system used by default in Centos 7 system
• SWAP, SWAP file system
  • Creating swap partitions for Linux systems
• Other file system types supported by Linux
  • FAT16 FAT32 NTFS EXT4 JFS...

3, Steps to add a hard disk under Linux

• Step 1: add a hard disk
• Step 2: partition
• Step 3: format
• Step 4: Mount
  Add two hard disks sdb and sdc to the system
  
  Partition the hard disk with fdisk command
  
  
  After the partition is completed, check the partition information. Use the lsblk command to view the hard disk information. - f means to view the details
  The blkid command checks the formatted file types and UUIDs of all partitions in the system
  
  Use the mkfs command to format the partition
  
  Mount the partition with the mount command (mount is used for temporary mounting, and permanent mounting needs to be written into the configuration file / etc/fstab)
  
  
• Use mount -a to take the configuration file into effect immediately
• Use the umount command to unload parameters, which can be used with the partition or mount point umount /dev/sdb1 or umount /test

4, Add SWAP partition

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

The changes remain in memory until you decide to write the changes to disk.
Think twice before using the write command.


command(input m get help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p): p
 Partition number (2-4，Default 2): 2
 Start sector (10487808-41943039，The default is 10487808): 
The default value 10487808 will be used
Last a sector, +a sector or +size{K,M,G} (10487808-41943039，The default is 41943039): +5G
 Partition 2 is set to Linux Type, size set to 5 GiB

command(input m get help): t
 Partition number (1,2，Default 2): 2
Hex code(input L List all codes): l

 0  empty              twenty-four  NEC DOS         81  Minix / used Linu bf  Solaris        
 1  FAT12           27  Hidden NTFS Win 82  Linux exchange / So c1  DRDOS/sec (FAT-
 2  XENIX root      39  Plan 9          83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  84  OS/2 Hidden C:  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     85  Linux extend      c7  Syrinx         
 5  extend            41  PPC PReP Boot   86  NTFS Volume set       da  Non file system data 
 6  FAT16           42  SFS             87  NTFS Volume set       db  CP/M / CTOS / .
 7  HPFS/NTFS/exFAT 4d  QNX4.x          88  Linux pure text    de  Dell tool      
 8  AIX             4e  QNX4.x Part 2 8 e  Linux LVM       df  BootIt         
 9  AIX Can start      4f  QNX4.x Part 3 93  Amoeba          e1  DOS visit       
 a  OS/2 Launch manager 50  OnTrack DM      94  Amoeba BBT      e3  DOS R/O        
 b  W95 FAT32       51  OnTrack DM6 Aux 9f  BSD/OS          e4  SpeedStor      
 c  W95 FAT32 (LBA) 52  CP/M            a0  IBM Thinkpad Hugh eb  BeOS fs        
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a5  FreeBSD         ee  GPT            
 f  W95 extend (LBA)  54  OnTrackDM6      a6  OpenBSD         ef  EFI (FAT-12/16/
10  OPUS            55  EZ-Drive        a7  NeXTSTEP        f0  Linux/PA-RISC  
11  Hidden FAT12    56  Golden Bow      a8  Darwin UFS      f1  SpeedStor      
12  Compaq diagnosis     5c  Priam Edisk     a9  NetBSD          f4  SpeedStor      
14  Hidden FAT16 <3 61  SpeedStor       ab  Darwin start-up     f2  DOS secondary       
16  Hidden FAT16    63  GNU HURD or Sys af  HFS / HFS+      fb  VMware VMFS    
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE 
18  AST Intelligent sleep    sixty-five  Novell Netware  b8  BSDI swap       fd  Linux raid automatic
1b  Hidden W95 FAT3 70  DiskSecure Duoqi bb  Boot Wizard latent  fe  LANstep        
1c  Hidden W95 FAT3 75  PC/IX           be  Solaris start-up    ff  BBT            
1e  Hidden W95 FAT1 80  used Minix       
Hex code(input L List all codes): 82
 Partitioned“ Linux"Change the type of to“ Linux swap / Solaris"

command(input m get help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Synchronizing disks.
[root@localhost ~]# 

• Format swap swap partition using mkswap command