UbiquityPreserveHome

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Summary

Extend the installer to allow the user to install Ubuntu while preserving the /home directory. The steps for this process can be found here.

Release Note

Ubuntu now supports installations that preserve the /home directory when it already exists. To do this, manual partitioning must be used, and the partition on which data is to be preserved must not be marked for formatting.

Rationale

Along with being an often requested feature, this would allow users to perform what amounts to a repair install by installing Ubuntu over top of itself while preserving the /home directory.

Use Cases

  • Joe installed Ubuntu and corrupted the system settings and files to the point where he wants to install Ubuntu again. He does not want to lose his documents and account settings.
  • Bob has Ubuntu 6.06 installed, but wants to try Ubuntu 8.04. He does not want to have to upgrade multiple times or risk upgrading straight to 8.04.

Design

We will add functionality to partman and ubiquity that checks to see if the requested root partition is not empty and contains a /home directory. If this is the case, debconf will present the user with a question similiar to the following:

This filesystem already seems to have some content on it.  Do you want to preserve this data and remove the following:
...list of directories and top-level files to be removed...

This question will be preseedable, so that OEMs can blindly say yes to it.

Implementation

Provided that the filesystem meets the requirements (ext3, not empty, has /home) and the user selects the preserve option, the following will be removed before the file copy process starts:

/bin
/boot
/dev
/etc
/lib
/lib32
/lib64
/proc
/sbin
/usr
/var
/sys
/initrd*
/vmlinuz*

Everything else will be preserved. This includes, at a minimum:

/home
/srv
/root
  • The installer will ignore failures to remove any of these items. If a directory is serving as a mountpoint it will produce EBUSY on rm, for example.
  • If /home is not a directory, such as the case where /home is just a symlink, remove it.
  • If the user created during the install already exists in /home, reuse the UID and GID from /home for that user by preseeding them.

UI Changes

There will be no changes to the user interface aside from the question dialog. This feature should be mostly transparent to the user.

Migration

  • /etc/skel will not be imported.
  • For the initial implementation, the installer will not attempt to recreate entries in /etc/fstab for any users it finds in /home.

Test/Demo Plan

Installs of Ubuntu over-top of itself will be used to test this feature.

BoF agenda and discussion

remove: /bin /boot /dev /etc /lib /lib32 /lib64 /proc /sbin /usr /var /sys /initrd* /vmlinuz*

preserve: /home /srv /root

warning saying, "this filesystem already seems to have some contents on it. If you want to go ahead I'll remove everything execept user data, but I'll remove the following:" "There is no guarentee, and you should back up your data." Needs to be a debconf question so OEMs can preseed it.

If the username already exists in /home, check the ID of that directory and use the same id. oem-config does the same thing. We just need to preseed the uid. Check gid as well.

don't worry about /etc/skel, but check user-setup to make sure it doesn't break things in this regard.

make sure /home is not a regular file. Remove it if it exists. It could be a symlink, in which case remove it.

Ignore failures to remove a directory. EBUSY will be triggered if it's a mount point.

Adding an option to the autopartitioner to enable all this functionality. Needs to meet the requirements: swap, ext3.

Logic to remove directories would need to be duplicated into a check for disk space available. Documentation: what we're removing we're not touching /etc/skel


CategorySpec

UbiquityPreserveHome (last edited 2009-09-24 05:19:16 by komputes)