Linux_7_swap_配置

简介：Swap分区在系统的物理内存不够用的时候，把硬盘空间中的一部分空间释放出来，以供当前运行的程序使用。那些被释放的空间可能来自一些很长时间没有什么操作的程序，这些被释放的空间被临时保存到Swap分区中，等到那些程序要运行时，再从Swap分区中恢复保存的数据到内存中。

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如何新建一个swap分区：

① 从硬盘上面分出一个分区(大概是内存的2倍)，类型为 82 Linux swap / So。

[root@localhost ~]# fdisk /dev/sdaWelcome 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.Command (m for help): pDisk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectorsUnits = sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk label type: dosDisk identifier: 0x000b9573   Device Boot      Start         End      Blocks   Id  System/dev/sda1   *        2048      411647      204800   83  Linux/dev/sda2          411648    20891647    10240000   83  LinuxCommand (m for help): q         [root@localhost ~]# fdisk /dev/sdaWelcome 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.Command (m for help): nPartition type:   p   primary (2 primary, 0 extended, 2 free)   e   extendedSelect (default p): pPartition number (3,4, default 3): First sector (20891648-41943039, default 20891648): Using default value 20891648Last sector, +sectors or +size{K,M,G} (20891648-41943039, default 41943039): +2GPartition 3 of type Linux and of size 2 GiB is setCommand (m for help): T    Partition number (1-3, default 3): 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 b11  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 auto1b  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      Hex code (type L to list all codes): 82Changed type of partition 'Linux' to 'Linux swap / Solaris'Command (m for 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 atthe next reboot or after you run partprobe(8) or kpartx(8)Syncing disks.

②刷一下分区表。

[root@localhost ~]# partprobe Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.

③格式化新建的分区（刚刚新建的分区是 /dev/sda3）

[root@localhost ~]# mkswap /dev/sda3mkswap: /dev/sda3: warning: wiping old swap signature.Setting up swapspace version 1, size = 2097148 KiBno label, UUID=0231b39a-b9d3-4161-889f-5a35abe92983

④挂载刚刚格式化的SWAP分区

vim /etc/fstab [进入fstab，修改fstab，增加swap 挂载信息]

UUID=58a2d551-6d2a-40cb-98e5-1b73f47ad81e swap swap defaults 0 0

⑤使用命令 swapon -a 挂载swapon

⑥一些常用的swap 命令

[root@localhost ~]# swapon -a[root@localhost ~]# swapon -s(列出挂载的swap)Filename                                Type            Size    Used    Priority/dev/sda3                               partition       2097148 0       -1[root@localhost ~]# swapoff -a（卸载fstab中挂载的swap）[root@localhost ~]# swapon -s[root@localhost ~]# swapon -a[root@localhost ~]# swapon -sFilename                                Type            Size    Used    Priority/dev/sda3                               partition       2097148 0       -1[root@localhost ~]# swapoff /dev/sda3（通过分区卸载swap）[root@localhost ~]# [root@localhost ~]# swapon -s[root@localhost ~]#