partman fails to overwrite an already existing filesystem with btrfs

[Chris Samuel]

When trying the current daily install image for Kubuntu 14.04 I found that when I tried to overwrite an old install that had ext4 on /dev/sda6 with a new one with btrfs on /dev/sda6 it would keep telling me that the creation of /dev/sda6 had failed.

Looking at /var/log/syslog it's because mkfs.btrfs is detecting the existence of an ext4 filesystem and refusing to overwrite it unless it is passed the -f flag.

In the end I had to dd over the start of /dev/sda6 from /dev/zero to enable the install to work.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubiquity 2.17.3
ProcVersionSignature: Ubuntu 3.12.0-7.15-generic 3.12.4
Uname: Linux 3.12.0-7-generic x86_64
ApportVersion: 2.12.7-0ubuntu3
Architecture: amd64
CasperVersion: 1.336ubuntu1
CurrentDesktop: KDE
Date: Sun Jan 5 23:02:33 2014
InstallCmdLine: file=/cdrom/preseed/kubuntu.seed boot=casper maybe-ubiquity initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
LiveMediaBuild: Kubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140105)
MarkForUpload: True
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)