文档课题：增加swap空间大小
以下为swap由8g增加到9g的演练过程：
1、当前swap大小
[root@dbserver ~]# lsblk
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda             8:0    0  100G  0 disk
├─sda1          8:1    0    2G  0 part /boot
└─sda2          8:2    0   98G  0 part
  ├─rhel-root 253:0    0   55G  0 lvm  /
  ├─rhel-swap 253:1    0    8G  0 lvm  [SWAP]
  └─rhel-home 253:2    0   35G  0 lvm  /home
sr0            11:0    1 1024M  0 rom 
[root@dbserver ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           7821         818        6362          26         640        6687
Swap:          8191           0        8191
[root@dbserver ~]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/dm-1                               partition    8388604 0       -2
2、扩展swap分区
2.1、新磁盘方式
添加一块1g磁盘，并完成分区.
[root@dbserver ~]# lsblk -p
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
/dev/sda                    8:0    0  100G  0 disk
├─/dev/sda1                 8:1    0    2G  0 part /boot
└─/dev/sda2                 8:2    0   98G  0 part
  ├─/dev/mapper/rhel-root 253:0    0   55G  0 lvm  /
  ├─/dev/mapper/rhel-swap 253:1    0    8G  0 lvm  [SWAP]
  └─/dev/mapper/rhel-home 253:2    0   35G  0 lvm  /home
/dev/sdb                    8:16   0    1G  0 disk
└─/dev/sdb1                 8:17   0 1023M  0 part
/dev/sr0                   11:0    1 1024M  0 rom
说明：/dev/sdb1为新加磁盘分区
#将新加分区设置为交换区.
[root@dbserver ~]# mkswap /dev/sdb1
Setting up swapspace version 1, size = 1047548 KiB
no label, UUID=cce40e01-b659-43aa-8801-a2a0cccf77eb
#启用交换分区/dev/sdb1
[root@dbserver ~]# swapon /dev/sdb1
[root@dbserver ~]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/dm-1                               partition       8388604 0       -2
/dev/sdb1                               partition       1047548 0       -3
[root@dbserver ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           7821         581        6770          15         469        6946
Swap:          9214           0        9214
#设置开机自动挂载
[root@dbserver ~]# echo "/dev/sdb1 swap swap defaults 0 0" >> /etc/fstab
说明：第一个0表示不要备份，第二0表示系统开机过程中不需要检验.
2.2、dd方式
dd方式增加swap空间.
[root@dbserver ~]# dd if=/dev/zero of=/swap01 bs=1024 count=1048572      #创建大小为1024m的文件
1048572+0 records in
1048572+0 records out
1073737728 bytes (1.1 GB) copied, 11.7121 s, 91.7 MB/s
说明：
bs=bytes：同时设置读入/输出的块大小为bytes个字节
count=blocks：仅拷贝blocks个块，块大小等于bs指定的字节数
[root@dbserver ~]# mkswap /swap01
Setting up swapspace version 1, size = 1048568 KiB
no label, UUID=6d8a5cb5-2fb7-4bcf-acff-5eae904dc325
[root@dbserver ~]# swapon /swap01
swapon: /swap01: insecure permissions 0644, 0600 suggested.
[root@dbserver ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           7821         851        5276          26        1693        6640
Swap:         10238           0       10238
[root@dbserver ~]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/sdb1                               partition       1047548 0       -2
/dev/dm-1                               partition       8388604 0       -3
/swap01                                 file    1048568 0       -4
[root@dbserver ~]# echo "/swap01 swap swap defaults 0 0" >> /etc/fstab
[root@dbserver ~]# cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Thu Nov 25 20:55:05 2021
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/rhel-root   /                       xfs     defaults        0 0
UUID=d2c7f75a-b3f7-46b1-84bc-56e40c0c4c5d /boot                   xfs     defaults        0 0
/dev/mapper/rhel-home   /home                   xfs     defaults        0 0
/dev/mapper/rhel-swap   swap                    swap    defaults        0 0
/dev/sdb1 swap swap defaults 0 0
/swap01 swap swap defaults 0 0

说明：不挂载swap用swapoff /swap01.