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

From: Dominic Raferd
Subject: Re: [rdiff-backup-users] backup Windows to Linux file permissions
Date: Wed, 26 Aug 2015 10:15:11 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0

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

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.


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