變更 SWAP 大小

1. 使用 fdisk 分割出來的 /dev/vda5 無法改變大小，若要變更只能重新分割。查詢目前 /dev/vda5 的 swap 大小為 10236 bytes (10M)。
   

   [root@kvm7 ~]# swapon -s
   Filename            Type        Size    Used    Priority
   /dev/dm-0           partition   126972  0       -1
   /dev/vda5           partition   10236   0       -2
   

2. 先關閉 /dev/vda5 的 swap。
   

   [root@kvm7 ~]# swapoff /dev/vda5
   [root@kvm7 ~]# swapon -s
   Filename            Type        Size    Used    Priority
   /dev/dm-0           partition   126972  0       -1
   

3. fdisk 硬碟 /dev/vda，刪除 /dev/vda5，再重新分割一個 30M 的 vda5，且格式為 swap (82)。
   

   [root@kvm7 ~]# fdisk /dev/vda 
   Welcome 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): p
   
   Disk /dev/vda: 4294 MB, 4294967296 bytes, 8388608 sectors
   Units = sectors of 1 * 512 = 512 bytes
   Sector size (logical/physical): 512 bytes / 512 bytes
   I/O size (minimum/optimal): 512 bytes / 512 bytes
   Disk label type: dos
   Disk identifier: 0x00094fcc
   
      Device Boot      Start         End      Blocks   Id  System
   /dev/vda1   *        2048      411647      204800   83  Linux
   /dev/vda2          411648     7579647     3584000   8e  Linux LVM
   /dev/vda3         7579648     7845887      133120   8e  Linux LVM
   /dev/vda4         7845888     8388607      271360    5  Extended
   /dev/vda5         7847936     7868415       10240   82  Linux swap / Solaris
   
   Command (m for help): d
   Partition number (1-5, default 5): 
   Partition 5 is deleted
   
   Command (m for help): n
   All primary partitions are in use
   Adding logical partition 5
   First sector (7847936-8388607, default 7847936): 
   Using default value 7847936
   Last sector, +sectors or +size{K,M,G} (7847936-8388607, default 8388607): +30M
   Partition 5 of type Linux and of size 30 MiB is set
   
   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 at
   the next reboot or after you run partprobe(8) or kpartx(8)
   Syncing disks.
   

4. 重新偵測新的分割表。
   

   [root@kvm7 ~]# partprobe 
   [root@kvm7 ~]# kpartx /dev/vda
   vda1 : 0 409600 /dev/vda 2048
   vda2 : 0 7168000 /dev/vda 411648
   vda3 : 0 266240 /dev/vda 7579648
   vda4 : 0 2 /dev/vda 7845888
   vda5 : 0 61440 /dev/vda 7847936
   

5. 將 /dev/vda5 格式化為 swap。
   

   [root@kvm7 ~]# mkswap /dev/vda5
   mkswap: /dev/vda5: warning: wiping old swap signature.
   Setting up swapspace version 1, size = 30716 KiB
   no label, UUID=e0cb3290-ecc4-488f-8b18-4a0f2235c9ea
   

6. 再從 /etc/fstab 中的設定啟動所有的 swap。
   

   [root@kvm7 ~]# swapon -a
   

7. 查詢啟動的 swap，除了原有的 /dev/dm-0 外，/dev/vda5 有 30716 bytes (30M)。
   

   [root@kvm7 ~]# swapon -s
   Filename            Type        Size    Used    Priority
   /dev/dm-0           partition   126972  0       -1
   /dev/vda5           partition   30716   0       -2