[Bug 684309] Re: Ubiquity Advanced Partitioning - Converting/Using ext4 to ext2 without formating formats the partition without warning

[James Hunt]

To be clear, I'm seeing the problem, but the checkbox *is* checked for
me:

1) Select an ext4 partition
2) Click "Change..."
3) Set "use as" to ext2
4) Do not check the "Format the partition" checkbox
5) Specify a mount point.
6) Click OK

At this point, the "Format?" column now has a tick against the ext4
filesystem with type shown as "ext2".

The problem seems to manifest itself if you specify a partition to be
mounted as a different type to how it was originally formatted.
Examples:

- If you format a partition to ext4, and mount it as ext4 but select do not format, ubiquity will not reformat.
- If you format a partition to ext4, and mount it as ext2 but select do not format, ubiquity will silently reformat (as reported).
- If you format a partition to ext4, and mount it as ext3 but select do not format, ubiquity will silently reformat.
- If you format a partition to ext2, and mount it as ext3 but select do not format, ubiquity will silently reformat.

What is happening is that
/lib/partman/choose_method/25filesystem/do_option is iterating through
the list of valid filesystems.

Here, we have a scenario where the existing partition is ext4 and the
user has selected ext2. Since the FS types do not match ($existing is
'no'), it decides that the partition needs to be formatted. Normally,
this would be an entirely reasonable outcome but for the fact that:

- ext4 is backwards compatible with ext3 and ext2.
- ext3 is backwards compatible with ext2.

One solution therefore would be to add logic to
/lib/partman/choose_method/25filesystem/do_option to special-case ext*
filesystems and only reformat if attempting to mount say ext2 as ext4.
However, clearly, ubiquity also needs to ask for user confirmation
before reformatting.

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https://bugs.launchpad.net/bugs/684309

Title:
  Ubiquity Advanced Partitioning - Converting/Using ext4 to ext2 without
  formating formats the partition without warning

Status in “ubiquity” package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: ubiquity

  Ubiquity Advanced Partitioning - Converting ext4 to ext2 without
  formatting formats the partition without warning

  ProblemType: Bug
  DistroRelease: Ubuntu 10.10
  Package: ubiquity 2.4.8
  ProcVersionSignature: Ubuntu 2.6.35-22.33-generic 2.6.35.4
  Uname: Linux 2.6.35-22-generic i686
  NonfreeKernelModules: wl
  Architecture: i386
  Date: Thu Dec  2 17:02:57 2010
  LiveMediaBuild: Ubuntu 10.10 "Maverick Meerkat" - Release i386 (20101007)
  ProcEnviron:
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: ubiquity

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