1、关闭虚拟机，找到需要扩容的硬盘，修改为新的容量80GB，应用保存。

2、打开VM，进入系统，使用lsblk可以看到硬盘容量已经变为80GB，但硬盘根分区还没有扩容，使用df查看根文件系统也没有扩容。

[192.168.2.108] alpha@mascot.x ~ $ lsblk 
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0 111.9M  1 loop /snap/lxd/24322
loop1    7:1    0  53.3M  1 loop /snap/snapd/19457
loop2    7:2    0  63.4M  1 loop /snap/core20/1974
sda      8:0    0    80G  0 disk 
├─sda1   8:1    0     1M  0 part 
└─sda2   8:2    0    25G  0 part /
sr0     11:0    1  1024M  0 rom  
[192.168.2.108] alpha@mascot.x ~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           392M  1.1M  391M   1% /run
/dev/sda2        25G  7.7G   16G  33% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           392M  4.0K  392M   1% /run/user/1000

3、使用parted命令修改分区大小：

sudo parted /dev/sda

运行parted命令后，输入help查看命令列表。

[192.168.2.108] alpha@mascot.x ~ $ sudo parted /dev/sda
[sudo] password for alpha: 
GNU Parted 3.4
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) help                                                             
  align-check TYPE N                       check partition N for TYPE(min|opt) alignment
  help [COMMAND]                           print general help, or help on COMMAND
  mklabel,mktable LABEL-TYPE               create a new disklabel (partition table)
  mkpart PART-TYPE [FS-TYPE] START END     make a partition
  name NUMBER NAME                         name partition NUMBER as NAME
  print [devices|free|list,all|NUMBER]     display the partition table, available devices, free space, all found partitions, or a particular
        partition
  quit                                     exit program
  rescue START END                         rescue a lost partition near START and END
  resizepart NUMBER END                    resize partition NUMBER
  rm NUMBER                                delete partition NUMBER
  select DEVICE                            choose the device to edit
  disk_set FLAG STATE                      change the FLAG on selected device
  disk_toggle [FLAG]                       toggle the state of FLAG on selected device
  set NUMBER FLAG STATE                    change the FLAG on partition NUMBER
  toggle [NUMBER [FLAG]]                   toggle the state of FLAG on partition NUMBER
  unit UNIT                                set the default unit to UNIT
  version                                  display the version number and copyright information of GNU Parted
(parted)  

 输入print命令，打印当前分区表，会提示有可用空间，需要修复GPT，输入Fix修复：

(parted) print                                                            
Warning: Not all of the space available to /dev/sda appears to be used, you can fix the GPT to use all of the space (an extra 115343360
blocks) or continue with the current setting? 
Fix/Ignore? Fix
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sda: 85.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  2097kB  1049kB                     bios_grub
 2      2097kB  26.8GB  26.8GB  ext4

(parted) 

 修复GPT之后，可以输入print free查看可用的空间：

(parted) print free                                                       
Model: ATA VBOX HARDDISK (scsi)
Disk /dev/sda: 85.9GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name  Flags
        17.4kB  1049kB  1031kB  Free Space
 1      1049kB  2097kB  1049kB                     bios_grub
 2      2097kB  26.8GB  26.8GB  ext4
        26.8GB  85.9GB  59.1GB  Free Space

(parted) 

继续 输入resizepart 2 100%命令，将分区2扩容100%可用空间，输入Yes确认操作：

(parted) resizepart 2 100%                                                
Warning: Partition /dev/sda2 is being used. Are you sure you want to continue?
Yes/No? Yes
(parted)  

 输入q退出parted命令，再用lsblk查看，根分区大小已经变成80G，但使用df查看根文件系统，还是25G，没有扩容。

(parted) q                                                                
Information: You may need to update /etc/fstab.

[192.168.2.108] alpha@mascot.x ~ $ lsblk                                  
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0  63.4M  1 loop /snap/core20/1974
loop1    7:1    0 111.9M  1 loop /snap/lxd/24322
loop2    7:2    0  53.3M  1 loop /snap/snapd/19457
loop3    7:3    0  38.8M  1 loop /snap/snapd/21759
loop4    7:4    0  63.9M  1 loop /snap/core20/2318
loop5    7:5    0    87M  1 loop /snap/lxd/28373
sda      8:0    0    80G  0 disk 
├─sda1   8:1    0     1M  0 part 
└─sda2   8:2    0    80G  0 part /
sr0     11:0    1  1024M  0 rom  
[192.168.2.108] alpha@mascot.x ~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           392M  1.1M  391M   1% /run
/dev/sda2        25G  7.9G   16G  35% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           392M  4.0K  392M   1% /run/user/1000

4、使用resize2fs命令更新文件系统大小，再用df查看根文件系统大小已经更新：

sudo resize2fs /dev/sda2

[192.168.2.108] alpha@mascot.x ~ $ sudo resize2fs /dev/sda2 
resize2fs 1.46.5 (30-Dec-2021)
Filesystem at /dev/sda2 is mounted on /; on-line resizing required
old_desc_blocks = 4, new_desc_blocks = 10
The filesystem on /dev/sda2 is now 20971003 (4k) blocks long.

[192.168.2.108] alpha@mascot.x ~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           392M  1.1M  391M   1% /run
/dev/sda2        79G  8.1G   68G  11% /
tmpfs           2.0G     0  2.0G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
tmpfs           392M  4.0K  392M   1% /run/user/1000

结束。

参考：

ubuntu 扩展分区并将剩余空间添加到现有逻辑卷中_ubuntu扩展分区大小 将一个磁盘加到另一个当中-CSDN博客