【Linux系统KVM虚拟机实战】LVM逻辑卷之扩展Swap交换分区

2023-08-03 160

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简介： 【Linux系统KVM虚拟机实战】LVM逻辑卷之扩展Swap交换分区

@TOC

一、Swap分区介绍

Linux中Swap（即：交换分区），类似于Windows的虚拟内存，就是当内存不足的时候，把一部分硬盘空间虚拟成内存使用，从而解决内存容量不足的情况。

二、检查本地系统环境

1.检查系统版本

[root@server001 ~]# cat /etc/os-release 
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

2.检查系统内核

[root@server001 ~]# uname -r 
3.10.0-957.el7.x86_64

三、检查本地磁盘状态

1.检查swap大小

[root@server001 ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           1837        1340          97           2         399         291
Swap:          2047        1046        1001

2.检查物理磁盘分区

使用lsblk命令检查磁盘分区情况

[root@server001 ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0              11:0    1  4.3G  0 rom  
vda             252:0    0  150G  0 disk 
├─vda1          252:1    0    1G  0 part /boot
└─vda2          252:2    0  149G  0 part 
  ├─centos-root 253:0    0   50G  0 lvm  /
  ├─centos-swap 253:1    0    2G  0 lvm  [SWAP]
  └─centos-home 253:2    0   97G  0 lvm  /home

3.查看PV状态

[root@server001 ~]# pvdisplay 
  --- Physical volume ---
  PV Name               /dev/vda2
  VG Name               centos
  PV Size               <149.00 GiB / not usable 3.00 MiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              38143
  Free PE               1
  Allocated PE          38142
  PV UUID               kZK4n1-OQbf-7uSQ-f0QI-PwfF-W8bh-zDQPNY

4.查看VG卷组状态

[root@server001 ~]# vgdisplay
  --- Volume group ---
  VG Name               centos
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <149.00 GiB
  PE Size               4.00 MiB
  Total PE              38143
  Alloc PE / Size       38142 / 148.99 GiB
  Free  PE / Size       1 / 4.00 MiB
  VG UUID               nxeB2C-4fW1-HijW-n2Bi-P1pN-p2Cv-rvjYZ4

5.查看LVM逻辑卷状态

[root@server001 ~]# lvdisplay 
  --- Logical volume ---
  LV Path                /dev/centos/swap
  LV Name                swap
  VG Name                centos
  LV UUID                71m8Iu-dxW6-dGiV-jnkC-ZCQn-BEAA-Yqnf3O
  LV Write Access        read/write
  LV Creation host, time kvm01, 2022-11-15 00:58:26 +0800
  LV Status              available
  # open                 2
  LV Size                2.00 GiB
  Current LE             512
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1

  --- Logical volume ---
  LV Path                /dev/centos/home
  LV Name                home
  VG Name                centos
  LV UUID                Of3kcY-tc4y-tyx5-VuBh-d7F7-10Zk-qZFHOE
  LV Write Access        read/write
  LV Creation host, time kvm01, 2022-11-15 00:58:26 +0800
  LV Status              available
  # open                 1
  LV Size                96.99 GiB
  Current LE             24830
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2

  --- Logical volume ---
  LV Path                /dev/centos/root
  LV Name                root
  VG Name                centos
  LV UUID                hawN56-mPFc-5dPA-NB72-sHYR-hwyF-okC1DL
  LV Write Access        read/write
  LV Creation host, time kvm01, 2022-11-15 00:58:27 +0800
  LV Status              available
  # open                 1
  LV Size                50.00 GiB
  Current LE             12800
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

四、给KVM虚拟机新增硬盘

1.查看虚拟机列表

给KVM虚拟机新增硬盘操作，都在宿主机上进行操作。
```bash
[root@server ~]# virsh list --all

Id Name State

7 kvm01 running

ikuai shut off

KVM-qunhui shut off


## 2.关闭KVM虚拟机

```bash
[root@server ~]# virsh shutdown kvm01
Domain kvm01 is being shutdown

3.查看KVM虚拟机磁盘位置

[root@server ~]#  virsh dumpxml kvm01 |grep file
    <disk type='file' device='disk'>
      <source file='/nas/kvm/centos7.img'/>
    <disk type='file' device='cdrom'>
      <source file='/storage/kvm/CentOS-7-x86_64-DVD-1810.iso'/>

4.创建磁盘文件

[root@server ~]# qemu-img create -f qcow2 /nas/kvm/swap.qcow2 20G
Formatting '/nas/kvm/swap.qcow2', fmt=qcow2 size=21474836480 encryption=off cluster_size=65536 lazy_refcounts=off

5.给虚拟机新增硬盘

给虚拟机新增硬盘，配置永久生效。

[root@server ~]# virsh attach-disk kvm01 /nas/kvm/swap.qcow2  vdb --subdriver=qcow2  --config
Disk attached successfully

6.再次查看虚拟机磁盘信息


[root@server ~]#  virsh dumpxml kvm01 |grep file
    <disk type='file' device='disk'>
      <source file='/nas/kvm/centos7.img'/>
    <disk type='file' device='disk'>
      <source file='/nas/kvm/swap.qcow2'/>
    <disk type='file' device='cdrom'>
      <source file='/storage/kvm/CentOS-7-x86_64-DVD-1810.iso'/>

7.KVM虚拟机开机

[root@server ~]# virsh start kvm01
Domain kvm01 started

五、关闭当前swap分区

1.清理系统内存占用程序

关闭交换分区swapoff,要保证剩余内存>=swap的used,自我感觉swap会释放到内存中。
否则会报错swapoff failed: Cannot allocate memory

保证物理剩余内存充足后，查看内存状态

[root@server001 ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           1837         156        1113           1         567        1493
Swap:          2047          46        2001

2.关闭swap

[root@server001 ~]# swapoff /dev/mapper/centos-swap 
[root@server001 ~]# swapon -s

3.再次查看内存状态

[root@server001 ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           1837         177        1081           8         578        1465
Swap:             0           0           0

六、扩展swap分区大小

1.查看系统硬盘情况

[root@server001 ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sr0              11:0    1  4.3G  0 rom  
vda             252:0    0  150G  0 disk 
├─vda1          252:1    0    1G  0 part /boot
└─vda2          252:2    0  149G  0 part 
  ├─centos-root 253:0    0   50G  0 lvm  /
  ├─centos-swap 253:1    0    2G  0 lvm  
  └─centos-home 253:2    0   97G  0 lvm  /home
vdb             252:16   0   20G  0 disk

2.扩展卷组

[root@server001 ~]# pvcreate /dev/vdb
  Physical volume "/dev/vdb" successfully created.
[root@server001 ~]# vgextend centos /dev/vdb
  Volume group "centos" successfully extended

3.扩展swap逻辑卷

扩展逻辑卷，增加6G大小空间。

[root@server001 ~]#  lvextend -L +6G /dev/centos/swap 
  Size of logical volume centos/swap changed from 2.00 GiB (512 extents) to 8.00 GiB (2048 extents).
  Logical volume centos/swap successfully resized.

4.格式化分区

[root@server001 ~]# mkswap /dev/centos/swap 
mkswap: /dev/centos/swap: warning: wiping old swap signature.
Setting up swapspace version 1, size = 8388604 KiB
no label, UUID=82c55c8a-0b9c-4b57-82dc-570354fb90d3

5.启动swap分区

 swapon /dev/mapper/centos-swap

6.查看swap状态

[root@server001 ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           1837        1509          62          10         265         122
Swap:          8191           1        8190