How to resize the BTRFS root volume of a SLE Micro installation

This document (000021534) is provided subject to the disclaimer at the end of this document.

Environment

SLE Micro 5.5
SL Micro 6

Situation

The BTRFS root volume of a SLE Micro installation runs out of disk space and needs to be resized.

Resolution

The following example will concentrate on a single root device to explain the steps of the resize operation.
Keep in mind, changes to the partition table can have a catastrophic impact on the system.

Always make sure to have a backup before making changes to the partition table!

In this demo case the partitioning layout is as follows:

test:~ # parted -l /dev/sda
Model: VMware Virtual disk (scsi)
Disk /dev/sda: 64.4GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name      Flags
 1      1049kB  3146kB  2097kB               p.legacy  bios_grub
 2      3146kB  24.1MB  21.0MB  fat16        p.UEFI    boot, esp
 3      24.1MB  64.4GB  64.4GB  btrfs

The goal is to add more disk space to sda3 to expand the BTRFS root filesystem, the root disk will be resized from 50GB to 60GB:

test:~ # btrfs fi show /
Label: 'ROOT'  uuid: d1cdc219-d60c-4c45-a2a3-a174fd59230a
    Total devices 1 FS bytes used 4.73GiB
    devid    1 size 49.98GiB used 5.52GiB path /dev/sda3

1.) Resize the existing disk to the new size using the appropriate tools to accomplish this task.
2.) Rescan the device to be resized:

test:~ # echo 1 > /sys/block/<devicename>/device/rescan

for example:

test:~ # echo 1 > /sys/block/sda/device/rescan

3.) Resize the root partition using growpart:

test:~ # growpart /dev/sda 3
CHANGED: partition=3 start=47104 old: size=104810463 end=104857567 new: size=125781983 end=125829087

4.) Resize the BTRFS filesystem:

test:~ # btrfs fi resize max /.snapshots
Resize device id 1 (/dev/sda3) from 49.98GiB to max

5.) Check the new size of the filesystem:

test:~ # btrfs fi show /
Label: 'ROOT'  uuid: d1cdc219-d60c-4c45-a2a3-a174fd59230a
    Total devices 1 FS bytes used 4.74GiB
    devid    1 size 59.98GiB used 5.52GiB path /dev/sda3

Cause

Running the "btrfs fi resize max" command on the regular root volume mount point would result in the following error on a SLE Micro installation:

test:~ # btrfs fi resize max /
Resize device id 1 (/dev/sda3) from 19.98GiB to max
ERROR: unable to resize '/': Read-only file system

as the root volume is mounted read-only. "/.snapshots" is mounted read-write and using this volume the operation can be finished online successfully.

Additional Information

This example only illustrates how to resize a single disk with the root partition being the last. In case further partitions exist, the operation may become more complex. If in doubt, open a support case with SUSE Customer Support to discuss details before applying any changes to the partition table.

Disclaimer

This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.