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Old 11-11-2009, 03:30 PM   #1
digity
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Use DD while Linux is running?


I'm looking for a way to backup my Ubuntu 9.04 installation on schedule while its running. Can I back it up with DD while it's running? If not, how can I do so?
 
Old 11-11-2009, 04:00 PM   #2
Didier Spaier
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Just wondering... why use dd to make a backup ? rsync is more appropriate, IMHO. And of course you can use it while it's running.
 
Old 11-11-2009, 06:17 PM   #3
syg00
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In general no (simple) backup solution is valid for a running system. Unless of course you can be sure nothing being backed up is being updated. When I need to do something like that I do it from single user to minimize the exposure. And I agree, dd is about the worst option.
 
Old 11-12-2009, 03:50 PM   #4
digity
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DD because I haven't really heard of any real alternatives. I tried to set up a RSYNC backup solution before and it was just too difficult (I needed it to be secure/over SSH) so I nixed it.

I basically want to make a whole drive backup without having to disrupt the running server and that I can easily restore (from a recovery/restore boot disc) like ShadowProtect does for Windows or the built-in Windows backup feature for Windows Server 2008 and Vista/7.
 
Old 11-12-2009, 04:11 PM   #5
jefro
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Backula maybe?
 
Old 11-12-2009, 05:05 PM   #6
Didier Spaier
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Quote:
Originally Posted by digity View Post
I tried to set up a RSYNC backup solution before and it was just too difficult (I needed it to be secure/over SSH).
Why too difficult ? rsync seems to be the right tool through SSH, just read the manual.
 
Old 11-12-2009, 05:10 PM   #7
ramram29
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rsync will do it for you. What I recommend is to do an offline backup using a system rescue cd then you can do online backups using rsync after that.
 
Old 11-12-2009, 09:39 PM   #8
digity
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ramram29: good idea. I'll use that VMware ghettoVCB.sh script to do a offline style whole system backup twice a month (yes, it's a virtual machine) and use rsync for daily backups.

Didier: do you know of a good but easy to follow rsync over ssh tutorial/how-to for Ubuntu to a FTP server (is that even possible)?
 
Old 11-12-2009, 10:43 PM   #9
i92guboj
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Regardless of what people say above, no solution is ok for a running system. The issues are likely to be minor on a desktop system, on systems with higher loads the thing starts getting creepier.

The right solution to your problem is called "snapshotting", and it's a feature that some file systems have. In solaris there's zfs, which implements this feature. In linux there's no mature fs that supports it (btrfs does, but it's nowhere near mature, and the zfs port for linux is FUSE based, and it's not mature either). So, the only option that's left is to use lvm (logical volume manager).

A snapshot is basically a photo of your disk on its current state, you take the photo, then backup that. It's an oversimplified explanation of course, but the key is that this way you ensure that nothing is going to change while you are doing the backup, and so, the backup will be 100% consistent, no matter what your system is doing at the moment. Taking the snapshot is quick, just a second, and you can clean it afterward.

The only downside is that migrating to lvm if you are not using it already can be a pain if you don't have enough free space to do it incrementally. Another downside (if you are a GUI fan) is that there's no decent GUI for lvm (that I know of).

You can start googling for "lvm snapshot" and read a bit until you get the concept, then change that by "lvm snapshot backup" to discover the rest. As said, if you take this course of action, your main problem right now would be the migration to lvm.

ps. I guess you already know this by now, but *never ever* do a backup with dd of a system that's mounted as 'rw', you will get a broken fs image almost for sure. A single disk write is enough to get a broken fs inside your disk image, how bad that will be depends on the fs and the number of write operations.

Last edited by i92guboj; 11-12-2009 at 10:47 PM.
 
Old 11-13-2009, 03:05 AM   #10
Didier Spaier
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Quote:
Originally Posted by digity View Post
Didier: do you know of a good but easy to follow rsync over ssh tutorial/how-to for Ubuntu to a FTP server (is that even possible)?
In that regard, there is no difference between distributions AFAIK. And you are the admin so never follow blindly any advise

That said, some links follow:
http://ubuntuforums.org/showthread.php?t=238672
http://troy.jdmz.net/rsync/index.html
http://www.adamsinfo.com/rsync-over-...mated-backups/
http://sial.org/howto/rsync/
http://www.adamsinfo.com/rsync-over-...mated-backups/
http://www.unix-tutorials.com/go.php?id=3707

Anyhow, a good understanding of commands you type is necessary. For instance, not knowing enough cp command's options I recently ended up with files properly copied... But the timestamps, not preserved

Last edited by Didier Spaier; 11-13-2009 at 03:19 AM.
 
  


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