Re: [PLUG] Backing up Windows to Linux

[Rich Freeman via plug <plug@lists.phillylinux.org>]

On Fri, May 26, 2023 at 9:03 PM Walt Mankowski via plug
<plug@lists.phillylinux.org> wrote:
>
> On Fri, May 26, 2023 at 04:58:14PM -0400, JP Vossen via plug wrote:
> > `robocopy` will flatly refuse to copy--many things--if Outlook,
> > Edge, or Teams are in use.
>
> Windows will also flat-out refuse to let you attach an Excel
> spreadsheet to an Outlook email if you have the spreadsheet currently
> open in Excel, even if it's been saved. So there's definitely some
> sort of shenanigans going on behind the scenes.

To be fair, backing up open files in any OS is problematic.  Linux
will let a process with appropriate privileges do it, but the file
isn't necessarily in a clean state when it happens.  This is of course
why applications often have their own backup capabilities, which will
generate files in a clean state.

You can create filesystem-level snapshots, or block-device level ones
with something like LVM, and those will at least ensure the entire
filesystem is consistent at a point in time, as if the power had been
interrupted (a bit better than that if done at the filesystem level).
I believe this is roughly how VSS behaves - it creates a read-only
snapshot of things for the backup software.  I don't know the gory
details.

Windows tends to be more restrictive with open files in general.
Unix-like OSes will just let you delete them, and cleanup after the
file is closed.  An open file handle is just like another link.

I certainly agree with the sentiment that it is best if you can avoid
having to back up windows at all, but if I'm going to go to the
trouble I'd sooner pick a solution that does it as comprehensively as
possible.  Otherwise the simplest solutions probably will just do the
backup over SMB so that there is nothing client-side to manage.  VSS
does require a client-side install I believe - at least all the
solutions I've seen have one (burp and bacula in particular).  You
could of course still mount a windows share via SMB and run the client
on a linux machine, but then you don't get VSS.  If you want to do
hash-based backups and not mtime-based ones you'd need a local client
anyway if you don't want to send everything over the network.

-- 
Rich
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