My first tech blog post: Resizing a VM disk image [cheat sheet]

Much akin to my painful decision to buy a smartphone because I couldn't remember appointments I'd made, I'm deciding today to enter the tech blogsphere. I just spent way too long googling how to do something I once knew how to do without googling. So much struggle.

This first post is a super super sloppy how-to for making my dev VM's image bigger. The math/steps/somethings may be off because my laptop CRASHED in the middle of the partition resizing the first time (Thanks systemd. No, really. I have a coredump to prove it.), and I had to backtrack and fill in some blanks. Post-crash, I made sure to start a screen session on the server in the lab just in case.

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Background: My swap partition was at the end of the disk, so I wanted to grow the middle partition (to keep my data in tact), and then re-add the swap back to the end.

1. qemu-img resize ubuntu-15.img +25G

3. use parted to resize partitions:

[root@localhost ~]# parted /var/lib/libvirt/images/ubuntu-15.img

GNU Parted 3.1

Using /var/lib/libvirt/images/ubuntu-15.img

Welcome to GNU Parted! Type 'help' to view a list of commands.

[If I had the original print output you could see the original three partitions, but this just shows two because I'd done a recover to get the 2nd one back after I deleted (which is when my laptop kicked it) it so I knew it's old start.]

Number Start End Size File system Name Flags

1 1049kB 8389kB 7340kB prep

2 8389kB 15.4GB 15.4GB ext4

[my math:]

disk is now 42.9 G, so 2G swap, ~38G disk

38G is 39845888kB

start = 8389kB

end = 39845888 + 8389 = 39854277kB

rm 2

mkpart

name []

type: ext4

start? 8389kB

end? 39854277kB

mkpart

name [] swap

type: linux-swap

start? 39.9GB

end? 42.9GB

(parted) print

Model: (file)

Disk /var/lib/libvirt/images/ubuntu-15.img: 42.9GB

Sector size (logical/physical): 512B/512B

Partition Table: gpt

Disk Flags:

Number Start End Size File system Name Flags

1 1049kB 8389kB 7340kB prep

2 8389kB 39.9GB 39.8GB ext4

3 39.9GB 42.9GB 3093MB linux-swap(v1) swap

quit

4. use resize2fs to fill in filesystem into newly expanded partition

- Boot into VM

~> df -h shows that /dev/sda2 is /

~> sudo resize2fs /dev/sda2

[sudo] password for christy:

resize2fs 1.42.12 (29-Aug-2014)

Filesystem at /dev/sda2 is mounted on /; on-line resizing required

old_desc_blocks = 1, new_desc_blocks = 3

The filesystem on /dev/sda2 is now 9728000 (4k) blocks long.

5. Re-create swap

~> sudo mkswap /dev/sda3

spits out something I didn't copy, but it includes your new UUID:

Grab that now.

UUID= 1cc8a190-ef01-4b07-b139-e1cef94b379c

~> sudo swapon -U UUID

6. Update fstab

~> sudo vi /etc/fstab
 change UUID from old one for swap to new one 

~> mount -a 

7. ~> sudo vi /etc/initramfs-tools/conf.d/resume # update with new swap UUID

8. ~> sudo update-initramfs -u 

Magical.