[OT] Understanding Linux backup limitations

[Mark Haney]

Young wrote:


>>
> Mostly curiosity, but I'd like to see a solution. It's a shame for Linux 
> that a Windows backup program can create an image backup of a booted 
> system, but Linux can't.

Linux /can/.  The question that you pose is interesting.  Everyone so 
far has pointed out the main factor in why it's /preferable/ to unmount 
the drive (oh goodness, maybe I should say partition) before cloning, 
and this is the dynamic nature of files.

Windows shadow copy does virtually the same thing as unmounting the 
drive to back up, it takes a snapshot of the drive, dumps it into temp 
space, then backs up the data from there.  This allows for file changes 
to be made while getting you fairly recent copies of files.
> 
> My concerns are really for the SOHO users. Larger companies have 
> multiple systems, and probably a sys admin.

What concerns are these that aren't also concerns for larger companies 
and sys admins?
> 
> Creating an image backup of a Linux install is a pain. And because of 
> that it doesn't get done as often as it should. Or people backup only 
> their home directory. I know, for myself, that it's stopped me from 
> trying out certain things because the risk/reward/pain/time ratios just 
> weren't good enough. It's slowing down the learning process for me, and 
> I'll never really move to Linux unless this gets fixed, because I know 
> I'll end up skipping a backup.

What /kind/ of image backup are you talking about?  A bootable ISO?  A 
/ghost/ image?  What?  This doesn't really tell me anything other than 
maybe you still aren't aware of what linux has to offer on that end.  I 
suggest, however, if you are going to 'try out' things, you setup a 
development/test area (VM perhaps?) to have a go at those things.  That 
is something any tester will do so as not to screw up a production system.

> 
> And, while image backups aren't the only type of backup needed, the rest 
> of the backup programs available aren't very friendly either.

Again, /which/ backup programs have you tried?  You give no concrete 
examples, just statements that are not backed up with facts.

> 
> I think SOHO users need a GUI backup program that can create an image 
> backup, and then be set to auto create incremental or differential 
> backups on top that. I'd pay for that.

Yes, I'm sure they do.  I have one I use all the time, it's called 
'KitchenSync', it's a KDE app that can run in GNOME and it works great. 
  There's also a port of Time Machine for OSX that I hear works pretty well.

I will say this, building an image backup is one thing, trying to 
streamline in differential/incremental changes is not really a good idea.

Typical backup strategies involve having a relatively static /system/ 
area and a dynamic data area that are in different partitions or drives. 
  There's a reason for this and backups are one of the primary factors 
to this design.  Build a system image of a stable system, and archive 
it.  backup the data area regularly using your choice of backup methods, 
then, when an update to the core system is needed, verify the system 
backup is viable, update, test, the make a new backup image.  This is 
how it's done in the corporate world.  It's why new patches are tested 
relentlessly before dumping to production machines.  Because shit happens.

The point is, backups aren't 'point and click' like transferring songs 
to your Ipod.  There are other factors involved that need to be thought 
out.  Yes, it's easier now than it used to be, but any decently paranoid 
person will take the time to plan their backup strategy and stick to it. 
  This is one of those few items where 'set it and forget it' doesn't 
work too well.

Of course, this is my opinion based on years of saved bacon because of 
my paranoia.  YMMV.



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Mark Haney
Sr. Systems Administrator
ERC Broadband
(828) 350-2415

Call (866) ERC-7110 for after hours support