虚拟机下ubuntu使用df命令查看磁盘空间小于实际空间

使用vmbox安装了ubuntu server的虚拟机，分配了50G的磁盘空间，但是使用df命令查看，发现总的磁盘空间不足50G

root@ubuntu1:/home/lyh# df -h
Filesystem                         Size  Used Avail Use% Mounted on
udev                               1.9G     0  1.9G   0% /dev
tmpfs                              394M  1.1M  393M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv   24G   13G   11G  55% /
tmpfs                              2.0G     0  2.0G   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
tmpfs                              2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/loop1                          56M   56M     0 100% /snap/core18/2253
/dev/loop0                          56M   56M     0 100% /snap/core18/2246
/dev/loop4                          68M   68M     0 100% /snap/lxd/21545
/dev/loop3                          62M   62M     0 100% /snap/core20/1242
/dev/loop5                          68M   68M     0 100% /snap/lxd/21835
/dev/loop6                          33M   33M     0 100% /snap/snapd/13640
/dev/loop7                          43M   43M     0 100% /snap/snapd/14066
/dev/sda2                          976M  203M  707M  23% /boot
tmpfs                              394M     0  394M   0% /run/user/1000
/dev/loop8                          62M   62M     0 100% /snap/core20/1270

发现 /dev/mapper/ubuntu--vg-ubuntu--lv 只有24个G的空间

查看所有块设备，以及他们之间的依赖关系

root@ubuntu1:/home/lyh# lsblk
NAME                      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
loop0                       7:0    0 55.5M  1 loop /snap/core18/2246
loop1                       7:1    0 55.5M  1 loop /snap/core18/2253
loop3                       7:3    0 61.9M  1 loop /snap/core20/1242
loop4                       7:4    0 67.3M  1 loop /snap/lxd/21545
loop5                       7:5    0 67.2M  1 loop /snap/lxd/21835
loop6                       7:6    0 32.5M  1 loop /snap/snapd/13640
loop7                       7:7    0 42.2M  1 loop /snap/snapd/14066
loop8                       7:8    0 61.9M  1 loop /snap/core20/1270
sda                         8:0    0   50G  0 disk
├─sda1                      8:1    0    1M  0 part
├─sda2                      8:2    0    1G  0 part /boot
└─sda3                      8:3    0   49G  0 part
  └─ubuntu--vg-ubuntu--lv 253:0    0 24.5G  0 lvm  /
sr0                        11:0    1 1024M  0 rom

发现sda3实际有50个G的空间，但是 ubuntu--vg-ubuntu--lv 只有24.5个G，剩余的空间并没有显示

查看LVM卷组的信息

root@ubuntu1:/home/lyh# vgdisplay
  --- Volume group ---
  VG Name               ubuntu-vg
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <49.00 GiB
  PE Size               4.00 MiB
  Total PE              12543
  Alloc PE / Size       6272 / 24.50 GiB
  Free  PE / Size       6271 / <24.50 GiB
  VG UUID               QV4pAN-R1BR-42Ln-Vv4J-58Nb-uniH-0qizNA

发现还有24.5G的 Free空间未分配

lvextend -L 20G /dev/mapper/ubuntu--vg-ubuntu--lv      //增大或减小至20G
lvextend -L +10G /dev/mapper/ubuntu--vg-ubuntu--lv     //增加10G
lvreduce -L -10G /dev/mapper/ubuntu--vg-ubuntu--lv     //减小10G
lvresize -l  +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv   //按百分比扩容

resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv            //执行调整

例如：在我原有的磁盘上增加10个G

root@ubuntu1:/home/lyh# lvextend -L +10G /dev/mapper/ubuntu--vg-ubuntu--lv
  Size of logical volume ubuntu-vg/ubuntu-lv changed from 24.50 GiB (6272 extents) to 34.50 GiB (8832 extents).
  Logical volume ubuntu-vg/ubuntu-lv successfully resized.
root@ubuntu1:/home/lyh# resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv
resize2fs 1.45.5 (07-Jan-2020)
Filesystem at /dev/mapper/ubuntu--vg-ubuntu--lv is mounted on /; on-line resizing required
old_desc_blocks = 4, new_desc_blocks = 5
The filesystem on /dev/mapper/ubuntu--vg-ubuntu--lv is now 9043968 (4k) blocks long.
root@ubuntu1:/home/lyh# df -h
Filesystem                         Size  Used Avail Use% Mounted on
udev                               1.9G     0  1.9G   0% /dev
tmpfs                              394M  1.1M  393M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv   34G   13G   20G  39% /
tmpfs                              2.0G     0  2.0G   0% /dev/shm
tmpfs                              5.0M     0  5.0M   0% /run/lock
tmpfs                              2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/loop1                          56M   56M     0 100% /snap/core18/2253
/dev/loop0                          56M   56M     0 100% /snap/core18/2246
/dev/loop4                          68M   68M     0 100% /snap/lxd/21545
/dev/loop3                          62M   62M     0 100% /snap/core20/1242
/dev/loop5                          68M   68M     0 100% /snap/lxd/21835
/dev/loop6                          33M   33M     0 100% /snap/snapd/13640
/dev/loop7                          43M   43M     0 100% /snap/snapd/14066
/dev/sda2                          976M  203M  707M  23% /boot
tmpfs                              394M     0  394M   0% /run/user/1000
/dev/loop8                          62M   62M     0 100% /snap/core20/1270

可以看到，/dev/mapper/ubuntu--vg-ubuntu--lv 已经增加了10个G