Creating a Swap Partition

Creating a Swap Partition

1.   Use  fdisk /dev/vda  to open your disk in fdisk. (Use gdisk if you are using a disk with a GUID partition table.)

2.   Press  n  to add a new partition. Specify start and stop cylinders and size.

3.   Type  t  to change the partition type. If you are using fdisk, use partition type 82. If you are using gdisk, use partition type 8200.

4.   Use mkswap to format the partition as swap space. Use, for instance,  mkswap /dev/vda6  if the partition you have just created is /dev/vda6.

5.   Type  free -m . You see the amount of swap space that is currently allocated.

6.   Use swapon to switch on the newly allocated swap space. If, for instance, the swap device you have just created is /dev/vda6, use  swapon /dev/vda6  to activate the swap space.

7.   Type  free -m  again. You see that the new swap space has been added to your server.

[root@rhel7 ~]# fdisk -l

Disk /dev/sda: 21.5 GB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes
Disk label type: dos
Disk identifier: 0x0006c7ae

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *                        Linux
/dev/sda2                    8e  Linux LVM

Disk /dev/sdb:  MB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes
Disk label type: dos
Disk identifier: 0x0c16d904

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1                          Linux

Disk /dev/sdc:  MB,  bytes,  sectors    ----/dev/sdc是新添加的磁盘，未分区
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes

Disk /dev/mapper/rhel-root: 18.8 GB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes

Disk /dev/mapper/rhel-swap:  MB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes

[root@rhel7 ~]# fdisk /dev/sdc    ---在/dev/sdc磁盘上划分出一个100M的Swab分区/dev/sdc1
Welcome to fdisk (util-linux 2.23.).

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 0x3990990c.

Command (m for help): n
Partition type:
   p   primary ( primary,  extended,  free)
   e   extended
Select (default p): p
Partition number (-, default ):
First sector (-, default ):
Using default value
Last sector, +sectors or +size{K,M,G} (-, default ): +100M   ---输入大小100M
Partition  of type Linux and of size  MiB is set

Command (m for help): t
Selected partition
Hex code (type L to list all codes): L

   Empty             NEC DOS           Minix / old Lin bf  Solaris
   FAT12             Hidden NTFS Win   Linux swap / So c1  DRDOS/sec (FAT-
   XENIX root        Plan             Linux           c4  DRDOS/sec (FAT-
   XENIX usr       3c  PartitionMagic    OS/ hidden C:  c6  DRDOS/sec (FAT-
   FAT16 <32M        Venix        Linux extended  c7  Syrinx
   Extended          PPC PReP Boot     NTFS volume set da  Non-FS data
   FAT16             SFS               NTFS volume set db  CP/M / CTOS / .
   HPFS/NTFS/exFAT 4d  QNX4.x            Linux plaintext de  Dell Utility
   AIX             4e  QNX4.x 2nd part 8e  Linux LVM       df  BootIt
   AIX bootable    4f  QNX4.x 3rd part   Amoeba          e1  DOS access
 a  OS/ Boot Manag   OnTrack DM        Amoeba BBT      e3  DOS R/O
 b  W95 FAT32         OnTrack DM6 Aux 9f  BSD/OS          e4  SpeedStor
 c  W95 FAT32 (LBA)   CP/M            a0  IBM Thinkpad hi eb  BeOS fs
 e  W95 FAT16 (LBA)   OnTrack DM6 Aux a5  FreeBSD         ee  GPT
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a6  OpenBSD         ef  EFI (FAT-12/16/
  OPUS              EZ-Drive        a7  NeXTSTEP        f0  Linux/PA-RISC b
  Hidden FAT12      Golden Bow      a8  Darwin UFS      f1  SpeedStor
  Compaq diagnost 5c  Priam Edisk     a9  NetBSD          f4  SpeedStor
  Hidden FAT16 <   SpeedStor       ab  Darwin boot     f2  DOS secondary
  Hidden FAT16      GNU HURD or Sys af  HFS / HFS+      fb  VMware VMFS
  Hidden HPFS/NTF   Novell Netware  b7  BSDI fs         fc  VMware VMKCORE
  AST SmartSleep    Novell Netware  b8  BSDI swap       fd  Linux raid auto
1b  Hidden W95 FAT3   DiskSecure Mult bb  Boot Wizard hid fe  LANstep
1c  Hidden W95 FAT3   PC/IX           be  Solaris boot    ff  BBT
1e  Hidden W95 FAT1   Old Minix
Hex code (type L to list all codes):
Changed type of partition 'Linux' to 'Linux swap / Solaris'

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   g   create a new empty GPT partition table
   G   create an IRIX (SGI) partition table
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): p

Disk /dev/sdc:  MB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes
Disk label type: dos
Disk identifier: 0x3990990c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1                             Linux swap / Solaris

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@rhel7 ~]# fdisk -l

Disk /dev/sda: 21.5 GB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes
Disk label type: dos
Disk identifier: 0x0006c7ae

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *                        Linux
/dev/sda2                    8e  Linux LVM

Disk /dev/sdb:  MB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes
Disk label type: dos
Disk identifier: 0x0c16d904

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1                          Linux

Disk /dev/sdc:  MB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes
Disk label type: dos
Disk identifier: 0x3990990c

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1                             Linux swap / Solaris

Disk /dev/mapper/rhel-root: 18.8 GB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes

Disk /dev/mapper/rhel-swap:  MB,  bytes,  sectors
Units = sectors of  *  =  bytes
Sector size (logical/physical):  bytes /  bytes
I/O size (minimum/optimal):  bytes /  bytes

[root@rhel7 ~]# mkswap /dev/sdc1   --格式化/dev/sdc1为swap分区
Setting up swapspace version , size =  KiB
no label, UUID=b74fbc00-3f2e-4dea-99da-a17de3f798c3

[root@rhel7 ~]# swapon /dev/sdc1   --激活swap分区
  [root@rhel7 ~]# free -m  --可以看到swap增加了100M
  total used free shared buff/cache available
  Mem: 1840   91   1603    8 144     1605
  Swap: 2147   0    2147
  [root@rhel7 ~]#