Extend btrfs root partition

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operating system
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Introduction

This article will demonstrate how to increase btrfs root partition size.

Use case:

  • In dual boot system (Fedora + Windows), use unsed disk space in Windows for Fedora.

Steps

Shrink Windows drive

  • Boot into Windows.
  • Shrink unsed drive using Disk Manager.

Create partition

  • Boot into Fedora.
  • Use gpart (CLI) or Disks (GUI) to create partition.
  • Check partition using lsblk. (nvme0n1p8 is newly created partition).
    ➜ sudo lsblk
[sudo] password for dhananjay:
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
zram0       252:0    0     8G  0 disk [SWAP]
nvme0n1     259:0    0 476.9G  0 disk
...
├─nvme0n1p6 259:6    0     1G  0 part /boot
├─nvme0n1p7 259:7    0 145.5G  0 part /home
│                                     /
└─nvme0n1p8 259:8    0 169.1G  0 part

Extend root

  • df output before extending.
    ➜ df
Filesystem      Size  Used Avail Use% Mounted on
...
/dev/nvme0n1p7  146G  113G   32G  79% /
...
  • Extend / using btrfs tool.
    ➜ sudo btrfs device add -f /dev/nvme0n1p8 /
Performing full device TRIM /dev/nvme0n1p8 (169.14GiB) ...
  • df output after extending.
    ➜ df
Filesystem      Size  Used Avail Use% Mounted on
...
/dev/nvme0n1p7  315G  113G  201G  37% /
...
  • That’s all!

Balancing data between 2 partitions (Optional)

  • Check device usage.
    ➜ sudo btrfs device usage /
/dev/nvme0n1p7, ID: 1
   Device size:           145.48GiB
   Device slack:              0.00B
   Data,single:           138.01GiB
   Metadata,DUP:            4.00GiB
   System,DUP:             16.00MiB
   Unallocated:             3.46GiB

/dev/nvme0n1p8, ID: 2
   Device size:           169.14GiB
   Device slack:              0.00B
   Unallocated:           169.14GiB
  • Run following command to balance the data. (It takes time based on disk size.)
    ➜ sudo btrfs device usage /
  • Verify device usage.
    ➜ sudo btrfs device usage /
[sudo] password for dhananjay:
/dev/nvme0n1p7, ID: 1
   Device size:           145.48GiB
   Device slack:              0.00B
   Data,single:            72.00GiB
   Metadata,DUP:            2.00GiB
   System,DUP:             64.00MiB
   Unallocated:            71.42GiB

/dev/nvme0n1p8, ID: 2
   Device size:           169.14GiB
   Device slack:              0.00B
   Data,single:            96.00GiB
   Metadata,DUP:            2.00GiB
   Unallocated:            71.14GiB