学习笔记-swap交换分区

1. 创建swap交换分区

   CentOS7系统内容物理内存小于2GB，swap分区大小与物理内存大小相同

   物理内存大于2GB，swap分区分配2GB即可

2. 操作流程

   （1）添加新磁盘

   ➜  ~ fdisk -l | grep sd
   
   Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors
   /dev/sda1   *        2048     2099199     1048576   83  Linux
   /dev/sda2         2099200    41943039    19921920   83  Linux
   
   Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors			# 此磁盘为新加磁盘
   

   （2）配置分区

   1.开始分区
   ➜  ~ fdisk /dev/sdb
   
   2.配置分区
   Command (m for help): n		# 添加新分区
   Partition type:
      p   primary (0 primary, 0 extended, 4 free)
      e   extended
   Select (default p): p		# 添加主分区
   Using default response p
   Partition number (1-4, default 1): 		# 默认为1
   First sector (2048-41943039, default 2048):    	# 起始扇区，默认2048
   Using default value 2048
   Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): +1G		# 配置分区大小
   Partition 1 of type Linux and of size 1 GiB is set
   
   3.配置分区system ID
   t   change a partition's system id
   Command (m for help): t
   Selected partition 1‘
   Hex code (type L to list all codes): 82
   Changed type of partition 'Linux' to 'Linux swap / Solaris'
   
   4.保存分区
   Command (m for help): w
   The partition table has been altered!
   
   5.检查
   ➜  ~ lsblk -f
   NAME   FSTYPE LABEL UUID                                 MOUNTPOINT
   sda                                                      
   ├─sda1 xfs          5c316564-0fb2-4bcc-b8c4-64d2794f166b /boot
   └─sda2 xfs          7a1a2f3b-4174-4b67-bdf1-b0d768720487 /
   sdb                                                      
   └─sdb1 swap         006a3b8f-2745-4668-b0e1-361bbbedaf06 
   

   （3）格式化swap分区

   ➜  ~ mkswap /dev/sdb1		# 格式化所配置的swap分区
   Setting up swapspace version 1, size = 1048572 KiB
   no label, UUID=4b1985eb-5bc0-4fea-8f80-244d2c2e49eb
   

   （4）挂载swap分区

   1.挂载前状态（swap为0）
   ➜  ~ free -h
                 total        used        free      shared  buff/cache   available
   Mem:           974M         94M        745M        7.6M        134M        727M
   Swap:            0B          0B          0B
   
   2.挂载swap分区
   ➜  ~ swapon /dev/sdb1
   
   3. 挂载后状态
   ➜  ~ free -h
                 total        used        free      shared  buff/cache   available
   Mem:           974M         95M        744M        7.6M        134M        726M
   Swap:          1.0G          0B        1.0G
   
   4.卸载swap分区
   ➜  ~ swapoff /dev/sdb1
   ➜  ~ free -h
                 total        used        free      shared  buff/cache   available
   Mem:           974M         94M        745M        7.6M        134M        727M
   Swap:            0B          0B          0B
   

3. 拓展：系统分区ID

   说明：ID表（linux分区默认为83，swap分区为82） 
   Hex code (type L to list all codes): L
   
    0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris        
    1  FAT12           27  Hidden NTFS Win 82  Linux swap / 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 extended  c7  Syrinx         
    5  Extended        41  PPC PReP Boot   86  NTFS volume set da  Non-FS data    
    6  FAT16           42  SFS             87  NTFS volume set db  CP/M / CTOS / .
    7  HPFS/NTFS/exFAT 4d  QNX4.x          88  Linux plaintext de  Dell Utility   
    8  AIX             4e  QNX4.x 2nd part 8e  Linux LVM       df  BootIt         
    9  AIX bootable    4f  QNX4.x 3rd part 93  Amoeba          e1  DOS access     
    a  OS/2 Boot Manag 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 hi eb  BeOS fs        
    e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a5  FreeBSD         ee  GPT            
    f  W95 Ext'd (LBA) 54  OnTrackDM6      a6  OpenBSD         ef  EFI (FAT-12/16/
   10  OPUS            55  EZ-Drive        a7  NeXTSTEP        f0  Linux/PA-RISC b
   11  Hidden FAT12    56  Golden Bow      a8  Darwin UFS      f1  SpeedStor      
   12  Compaq diagnost 5c  Priam Edisk     a9  NetBSD          f4  SpeedStor      
   14  Hidden FAT16 <3 61  SpeedStor       ab  Darwin boot     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 SmartSleep  65  Novell Netware  b8  BSDI swap       fd  Linux raid auto
   1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid fe  LANstep        
   1c  Hidden W95 FAT3 75  PC/IX           be  Solaris boot    ff  BBT            
   1e  Hidden W95 FAT1 80  Old Minix