Re: [rdiff-backup-users] backup Windows to Linux file permissions

[Dominic Raferd]

On 22/08/2015 02:45, Leland Best wrote:
> Hi All,
>
> Since we're sort-of on this subject I'd like to ask a question/bring up
> an issue I ran into a couple years ago which, obviously, has never been
> resolved.
>
> On Fri, 2015-08-21 at 14:30 -0400, Patrik Dufresne wrote:
> > I've setup rdiff-backup to backup a windows computer...
> On a related note, have you ever restored one of these backups?  If so,
> has it correctly restored the Windows permissions/ACLs?  I only ask
> because when I've backed up and restored from/to Windows Vista and
> Windows 7, the restored Windows permissions are wrong.  Digging into
> 'rdiff-backup's metadata files seemed to show the permissions were
> stored correctly on the Linux box.  At least, they exactly matched the
> output of some-windows-command-line-program whose name I have now
> forgotten.  But on restore the results on the Windows box were very
> strange.  IIRC, extra groups were given access, permissions that were
> originally "inherited" were now not inherited, etc..  I've had this
> problem with both Cygwin and native versions of 'rdiff-backup', with
> both the 'stable' 1.2.8, and the 'unstable' 1.3.3 versions of
> 'rdiff-backup', and when backing up to both Linux and Windows machines.
>
> The only way I've found of reliably backing up and restoring a Windows
> box using 'rdiff-backup' is: Mirror the entire partition using e.g.
> 'ntfsclone', then use 'rdiff-backup' to back up the mirror file.  I've
> restored Windows boxes from "bare metal" using such backups and they
> work perfectly.  But wow is it unwieldy!
>
> Anyway, apologies if this is too off topic but it does seem somewhat
> related in that, for me anyway, 'rdiff-backup' and Windows do _not_ play
> nicely together regarding permissions.

Hi Leland

I too remain uncertain about rdiff-backup's interactions with Windows 
permissions, not least because I don't fully understand the latter. I 
always backup from Windows without ACLs and use rdiff-backup (1.2.8) 
only for data backup, not whole-system. But even here problems can 
arise; with some folders such as %APPDATA%\Thunderbird the permissions 
can get messed up on restoring - because of inheritance I believe.  To 
make it more confusing, the problem may not manifest itself immediately 
but a few days or weeks later - when the restored folder suddenly 
becomes inaccessible on the local machine.

After restoring with rdiff-backup to %APPDATA%\Thunderbird (or a 
subfolder thereof) I fix the permissions thus - must be at an 
administrator prompt:

icacls "%APPDATA%\Thunderbird" /reset /T /C /Q

This restores permissions for %APPDATA%\Thunderbird and all files and 
directories below it to the default inherited permissions. Obviously it 
assumes that the restored folder and all its contents *should* normally 
inherit all default permissions.

I have only used this under Windows 8.1 but I expect (hope) it would 
work the same for Windows 7-10. I think it is likely to work fine for 
anything in %APPDATA% (normally C:\Users\myname\AppData\Roaming), 
perhaps even anything in %USERPROFILE% (normally C:\Users\myname), but 
it is a workaround rather than a fix. Trying it on %WINDIR% would surely 
wreak havoc...

Re rdiff-backup and windows ACLs generally, the rdiff-backup 'features' 
page http://www.nongnu.org/rdiff-backup/features.html says 'ACLs are not 
supported on Mac OS X or Windows as those systems do not use standard 
POSIX.1e access controls'. And refer to a 2008 thread on this mailing 
list: 
http://www.backupcentral.com/phpBB2/two-way-mirrors-of-external-mailing-lists-3/rdiff-backup-23/patch-backing-up-windows-acls-90543/ 
- I am not sure if Josh's patch ever made it into a published version of 
rdiff-backup.

Dominic