Bug#597005: partman-base: Preserving partitions on install exposes alignment problem

["Anthony L. Awtrey" <tony@awtrey.com>]

Package: partman-base
Version: 144

While testing a preseeded install that preserves a data partition
(moving from lenny to squeeze), we discovered that the change from
cylinder to optimal alignment makes the preserved filesystem unusable.

Create a partition scheme like this in Lenny:

/     = 10G
swap  = 1G
/home = the rest

Set up a preseed recipe that preserves the /home partition (see attached
file for our example). We use simple-cdd to build custom installers that
use our preseed install file. The partition alignment for all partitions
is changed when the first two partitions are recreated and the /home
partition is no longer mountable after install.

I suppose it is very difficult to realign existing filesystems. Can the
partition alignment be mixed with new partitions taking advantage of the
potential performance benefits of the optimal setting, while preserving
the existing partitions/file systems alignment?

Tony

# Example recipe for partman
d-i     partman-auto/expert_recipe      string system ::                                \
                                          512 1024 10240 ext3                           \
                                            $primary{ }                                 \
                                            $bootable{ }                                \
                                            method{ format } format{ }                  \
                                            use_filesystem{ } filesystem{ ext3 }        \
                                            options/noatime{ noatime }                  \
                                            label{ root }                               \
                                            mountpoint{ / }                             \
                                          .                                             \
                                          512 1024 300% linux-swap                      \
                                            $primary{ }                                 \
                                            method{ swap } format{ }                    \
                                            label{ swap }                               \
                                          .                                             \
                                          512 1024 1000000000 ext3                      \
                                            $primary{ }                                 \
                                            method{ keep }                              \
                                            use_filesystem{ } filesystem{ ext3 }        \
                                            options/noatime{ noatime }                  \
                                            label{ home }                               \
                                            mountpoint{ /home }                         \
                                          .