Ability to shrink partitions might be useful in cases when you need to shrink one partition and expand another one. I had a problem where my root partition was too small, so the only way to expand root partition was to shrink home and expand root file system.

To manipulate XFS partitions you might need to install xfsprogs package. You can grow partition size using xfs_growfs. But unlike EXT4 file system there is no way to shrink partition. Good luck you’re fucked.

Solution

But there is a solution how to shrink partition. It’s not a straightforward solution, but it saved my hide, when my root partition was way too small.

  1. Backup partition image
  2. Delete old partition
  3. Create new smaller partition (make sure that image still fits partition)
  4. Restore image
  5. Edit fstab

Example

For this example, I have created a virtual machine with Ubuntu installation. There is /home (/dev/sda5) and / (/dev/sda1) partitions. In this case we will be shrinking home partition from ~8.6GB to 4GB.

List of partitions:

root@ubuntu:/home/ubuntu# fdisk -l
...

Disk /dev/sda: 16 GiB, 17179869184 bytes, 33554432 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x577dacac

Device     Boot    Start      End  Sectors  Size Id Type
/dev/sda1  *        2048 15624191 15622144  7.5G 83 Linux
/dev/sda2       15626238 33552383 17926146  8.6G  5 Extended
/dev/sda5       15626240 33552383 17926144  8.6G 83 Linux


Disk /dev/sdb: 4 GiB, 4294967296 bytes, 8388608 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 95A2ABE1-743B-4A77-9133-7EF3B3AF6F5A

Device     Start     End Sectors Size Type
/dev/sdb1   2048 8388574 8386527   4G Linux filesystem

As you can see from partition list, there is /dev/sdb1 this partition will be used to back up our /home partition.

Preparation

Probably you could shrink home partition using live system. But if you would like to shrink root partition you could not do it on a live system.

So in this example, I will demonstrate a method that should work even with resizing root partition. For this to work you’ll need to boot not from your hard drive, but from Live USB stick or CD.

In this case, I have chosen to use Live Ubuntu CD.

When you are running from the Live CD open terminal and change to root, because most of the commands require root access.

sudo su

Backing up image

For creating disk images I have chosen to use xfsdump application. It allows creating a backup of mounted file system. In most distributions xfsdump and xfsrestore are not installed by default.

Install xfsdump and xfsrestore: apt-get install xfsdump

Before making an image of home partition we need to mount it.

mkdir /mnt/home
mount /dev/sda5 /mnt/home

Also, we need to mount destination partition. This partition should be big enough to hold the backup image.

mkdir /mnt/external
mount /dev/sdb1 /mnt/external

Backup image creation:

xfsdump -l 0 -f /mnt/external/backup /mnt/home

When running xfs dump you must specify the backup file name. In this case image name is backup.

After running this command you’ll be asked to enter the label of backup. In this case I have used “home” as label.

Delete old partition

Unmount home partition.

umount /mnt/home

To delete the partition you can use your favorite application. It can be GParted or another tool.

In this example, I have used interactive command line utility fdisk.

fdisk /dev/sda
Welcome to fdisk (util-linux 2.29).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): d
Partition number (1,2,5, default 5): 5

Partition 5 has been deleted.

d stands for delete. 5th partition is home partition

Press w to write changes to disk.

Create new smaller partition

To create new partition you can use any tool you like, but for this example I have chose fdisk.

fdisk /dev/sda
Welcome to fdisk (util-linux 2.29).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Command (m for help): n
All space for primary partitions is in use.
Adding logical partition 5
First sector (15628286-33552383, default 15628288): (enter)
Last sector, +sectors or +size{K,M,G,T,P} (15628288-33552383, default 33552383): +4G

Created a new partition 5 of type 'Linux' and of size 4 GiB.

n command is for creating new partition. +4G means that new partition size will be 4GB.

Press w to write changes to disk.

Create XFS file system on new partition:

mkfs.xfs /dev/sda5

Mount partition:

 mount /dev/sda5 /mnt/home

Restore image

To restore XFS partition you need to know session ID. To find out image session id run this command:

xfsrestore -I | grep session

Output of this command:

session 0:
		session label:	"home"
		session id:	7a80f19f-ab34-4598-bf8f-dede406d50dc

So in our case session id is 7a80f19f-ab34-4598-bf8f-dede406d50dc.

Run xfsrestore:

xfsrestore -f /mnt/external/backup -S 7a80f19f-ab34-4598-bf8f-dede406d50dc /mnt/home

Output:

dede406d50dc /mnt/home
xfsrestore: using file dump (drive_simple) strategy
...
xfsrestore: Restore Summary:
xfsrestore:   stream 0 /mnt/external/backup OK (success)
xfsrestore: Restore Status: SUCCESS

Edit fstab

The new partition will have different UUID, because of that your system might not boot.

When you are shrinking /home, /root or other automatically mounted partition you’ll need to update fstab with new partition UUID.

Before rebooting mount your root file system and edit fstab file.

Run blkid to find out current UUID of disk.

blkid
/dev/sr0: UUID="2017-04-12-03-44-04-00" LABEL="Ubuntu 17.04 amd64" TYPE="iso9660" PTUUID="1b571474" PTTYPE="dos"
/dev/loop0: TYPE="squashfs"
/dev/sda1: UUID="3d2b0c24-2aae-4eb6-ae76-b15f3aca32f4" TYPE="xfs" PARTUUID="577dacac-01"
/dev/sda5: UUID="f359a7c4-bc72-416d-a50a-5869792c2832" TYPE="xfs" PARTUUID="577dacac-05"
/dev/sdb1: UUID="0882a8db-ae76-44de-9bbe-a453c727ff50" TYPE="xfs" PARTUUID="9f306132-b5fc-4bd5-8a85-a3f9d820276a"

In this case new UUID is 0882a8db-ae76-44de-9bbe-a453c727ff50. You should replace your partition UUID in fstab with your new partitions UUID.

mkdir /mnt/root
mount /dev/sda1 /mnt/root
vim /mnt/root/etc/fstab

Summary

That’s it, the solution was a little bit long-winded, but at least it works. If you know a simpler way to resize XFS partition feel free to share it in the comments section.