How to grow a mounted partition

grow-partition.md

1. Grow the disk in your hypervisor (Hyper-V: Edit Disk in Actions panel)

2. Apply the disk size change (you can do echo 1 | sudo tee /sys/class/block/sda/device/rescan instead of partprobe)

   $ sudo partprobe /dev/sda
   
   $ sudo dmesg | tail
   ...
   [4688278.217348] sd 2:0:0:0: Capacity data has changed
   [4688278.217583] sd 2:0:0:0: [sda] 83886080 512-byte logical blocks: (42.9 GB/40.0 GiB)
   [4688278.217661] sda: detected capacity change from 32212254720 to 42949672960
   
   $ sudo parted -l
   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 20971520 blocks) or continue with
   the current setting?
   Fix/Ignore? fix
   
   Disk /dev/sda: 42.9GB
   Sector size (logical/physical): 512B/512B
   Partition Table: gpt
   Disk Flags:
   
   Number  Start   End     Size    File system  Name  Flags
   ...
    2      538MB   32.2GB  31.7GB  ext4
   

3. Use growpart (from cloud-guest-utils package) to resize the required partition and write changes (alternatives: resizepart, cfdisk, parted).

    $ sudo growpart --verbose /dev/sda 2
    CHANGED: partition=2 start=1050624 old: size=61863903 end=62914527 new: size=82835423 end=83886047
   

4. Apply the partition size change (using resize2fs).

   $ sresize2fs /dev/sda2
   sresize2fs 1.46.2 (28-Feb-2021)
   Filesystem at /dev/sda2 is mounted on /; on-line resizing required
   old_desc_blocks = 4, new_desc_blocks = 5
   The filesystem on /dev/sda2 is now 10354427 (4k) blocks long.
   

5. Verify.

   $ sudo fdisk -l
   Disk /dev/sda: 40 GiB, 42949672960 bytes, 83886080 sectors
   ...
   
   Device       Start      End  Sectors  Size Type
   /dev/sda1     2048  1050623  1048576  512M EFI System
   /dev/sda2  1050624 83886046 82835423 39.5G Linux filesystem
   
   $ df -h
   Filesystem      Size  Used Avail Use% Mounted on
   ...
   /dev/sda2        39G   25G   13G  67% /