背景
kvm磁盘容量情况：硬盘分配了40G，系统没有使用LVM进行分区管理，根分区所挂载/dev/vda2随业务使用根分区剩余空间不足，需要对其进行数据无损的空间扩容。
p.s.:检测系统是否使用LVM进行分区管理的方法，执行下面命令即可（若没有返回信息则代表不是LVM分区方式）：
pvdisplay # 查看物理卷
vgdisplay # 查看卷组
lvdisplay # 查看逻辑卷
操作方法
kvm磁盘空间扩容
1、 虚拟机关机，防止磁盘数据损坏
2、 qemu-img命令可以通过resize选项对qcow2的格式虚拟磁盘镜像文件增加容量。
例如，对虚拟机的磁盘镜像文件扩充30G空间。
qemu-img resize system_os.qcow2 +30G
根分区数据无损扩容
1、虚拟机启动，此时lsblk可以看到vda磁盘的大小已经是扩容后的值，但是其分区vda1和vda2的值并没有更新。
[root@localhost ~]# lsblk
MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 252:0 0 70G 0 disk
├─vda1 252:1 0 2G 0 part /boot
└─vda2 252:2 0 38G 0 part /
vdb 252:16 0 12.7G 1 disk
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 64G 0 64G 0% /dev
tmpfs 64G 0 64G 0% /dev/shm
tmpfs 64G 29M 64G 1% /run
tmpfs 64G 0 64G 0% /sys/fs/cgroup
/dev/vda2 38G 27G 8.6G 76% /
tmpfs 64G 0 64G 0% /tmp
/dev/vda1 2.0G 65M 2.0G 4% /boot
tmpfs 13G 0 13G 0% /run/user/0
/dev/vdb iso9660 13G 13G 0 100% /mnt/cdrom
2、需要用到partprobe命令，如果没有的话安装parted包。
[root@localhost ~]# partprobe --help
-bash: partprobe: command not found
[root@localhost ~]# yum -y install parted
[root@localhost ~]# partprobe /dev/vda
3、接下来进行根分区扩容。
fdisk -l :查看当前磁盘的分区情况
fdisk /dev/vda对该磁盘进行管理，在此首先对原根分区对应的vda2删除，然后新增分区。操作中可以关注vda2的start值是否保持一致。
fdisk 操作命令：
p：打印出当前分区的情况
d：删除分区
n：新建分区
w：将分区表写入磁盘并退出
[root@localhost ~]# fdisk -l
Disk /dev/vda: 70 GiB, 75161927680 bytes, 146800640 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
Disklabel type: dos
Disk identifier: 0x247032e6
Device Boot Start End Sectors Size Id Type
/dev/vda1 2048 4194303 4192256 2G e W95 FAT16 (LBA)
/dev/vda2 4194304 83886079 79691776 38G 83 Linux
Disk /dev/vdb: 12.66 GiB, 13578602496 bytes, 26520708 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
[root@localhost ~]# fdisk /dev/vda
Welcome to fdisk (util-linux 2.35.2).
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: 70 GiB, 75161927680 bytes, 146800640 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
Disklabel type: dos
Disk identifier: 0x247032e6
Device Boot Start End Sectors Size Id Type
/dev/vda1 2048 4194303 4192256 2G e W95 FAT16 (LBA)
/dev/vda2 4194304 83886079 79691776 38G 83 Linux
Command (m for help): d
Partition number (1,2, default 2): 2
Partition 2 has been deleted.
Command (m for help): n
Partition type
p primary (1 primary, 0 extended, 3 free)
e extended (container for logical partitions)
Select (default p): p
Partition number (2-4, default 2): 2
First sector (4194304-146800639, default 4194304):
Last sector, +/-sectors or +/-size{K,M,G,T,P} (4194304-146800639, default 146800639):
Created a new partition 2 of type 'Linux' and of size 68 GiB.
Partition #2 contains a ext4 signature.Do you want to remove the signature? [Y]es/[N]o: n
Command (m for help): p
Disk /dev/vda: 70 GiB, 75161927680 bytes, 146800640 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
Disklabel type: dos
Disk identifier: 0x247032e6
Device Boot Start End Sectors Size Id Type
/dev/vda1 2048 4194303 4192256 2G e W95 FAT16 (LBA)
/dev/vda2 4194304 146800639 142606336 68G 83 Linux
Command (m for help): w
The partition table has been altered.
Syncing disks.
[root@localhost ~]# partprobe /dev/vda
#此时df看到的vda2的信息仍旧没有更新
[root@localhost ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
devtmpfs devtmpfs 64G 0 64G 0% /dev
tmpfs tmpfs 64G 0 64G 0% /dev/shm
tmpfs tmpfs 64G 29M 64G 1% /run
tmpfs tmpfs 64G 0 64G 0% /sys/fs/cgroup
/dev/vda2 ext4 38G 27G 8.6G 76% /
tmpfs tmpfs 64G 0 64G 0% /tmp
/dev/vda1 vfat 2.0G 65M 2.0G 4% /boot
tmpfs tmpfs 13G 0 13G 0% /run/user/0
/dev/vdb iso9660 13G 13G 0 100% /mnt/cdrom
接下来使用resize2fs指令对分区重新进行一次扫描识别就可以看到正确的分区容量了，此时扩容成功。
#由于vda2的type是ext4，ext*格式使用resize2fs，如果是xfs系统使用xfs_growfs
[root@localhost ~]# resize2fs /dev/vda2resize2fs 1.45.6 (20-Mar-2020)
Filesystem at /dev/vda2 is mounted on /; on-line resizing required
old_desc_blocks = 5, new_desc_blocks = 9
The filesystem on /dev/vda2 is now 17825792 (4k) blocks long.
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 64G 0 64G 0% /dev
tmpfs 64G 0 64G 0% /dev/shm
tmpfs 64G 29M 64G 1% /run
tmpfs 64G 0 64G 0% /sys/fs/cgroup
/dev/vda2 67G 27G 37G 43% /
tmpfs 64G 0 64G 0% /tmp
/dev/vda1 2.0G 65M 2.0G 4% /boot
tmpfs 13G 0 13G 0% /run/user/0
/dev/vdb 13G 13G 0 100% /mnt/cdrom
