rsync is bad

[Les Mikesell]

Paul Johnson wrote:
>
>>    Can't do that now Mike. I formatted the partition again for a fresh
>> start. I used a rsync method recommended and will comment on it's
>> workings. I fixed the recommended rsync method and used it to backup
>> this Ubuntu to /dev/hda7 again. The rsync ended with zero errors.
>>
>>    Here is the way I used rsync:
>> karl at karl-desktop:~$ cat /root/bin/rsync1
>> # This file is designed to backup my Ubuntu to the USB Hard Drive using
>> rsync
>> # Karl Larsen, 8 june 08
>> # rsync -vaHz --exclude '/proc' --exclude '/sys' --exclude '/media' /.
>> # /media/disk
>> rsync -vaH --exclude '/proc' --exclude 'sys' --exclude 'home' --exclude
>> '/mnt' /. /mnt
>>
>> The last line is what I used because I wanted the backup to go direct to
>> /dev/hda7 and it did.
>>
>>    Next I went to /mnt/etc/fstab and changed the uuid to the one I made
>> yesterday for /dev/hda7. Then I reboot and came up in the backup. It
>> found the kernel and the splash panel came on and there it stopped.
>>
>>    I rest my case. Rsync does not work as a backup because the backup
>> does not work. Period.
>>
>> Karl
>>
> 
> Rsync is not the right tool to try to clone a whole operating system.
> Whoever told you that it was is an, well, not knowledgable. Rsync is a
> great tool to copy files from one system to another and do so with
> lowest possible network traffic.  It is not very good at copying onto
> foreign filesystems, such as mounted Novell, openafs, or Windows
> shares.
> 
> If you want to copy an entire disk exactly, or an entire partition
> exactly, you should use a tool like "g4u". Stands for "ghost 4 unix."
> It is a bootable CD, which can access disk drives to copy them
> exactly, bit for bit.  Generally, you can't get a perfect copy of a
> running file system because files are constantly being accessed and
> changed.
> 
> Rsync won't copy the boot sector and your grub configuration generally
> will not be correct if you just copy files from one device to another.
> 
> If you want to copy the contents of a partition exactly, rsync have to
> have PERMISSIONS to open any file that it intends to copy.  Whoever
> told you that root access is not necessary is a, well, not
> knowledgable.  How in the world did you expect it to copy files that
> it does not have permission even to open?
> 
> Rsync's strength is in file copies ACROSS a network because it only
> copies the changed parts of files across.  When you use rsync on a
> computer to copy from one drive to another, it uses the local drive
> mode and it does not try to copy just the changed parts.  It is no
> better than running "cp -Ra x y" to copy recursively in archive mode.
> 
> Before I get carried away, I'm inclined to call Hitler on this thread.
> We are just throwing good effort after bad.

In case you weren't following, the rsync copy did work after he got the 
copies mounted correctly.   You are right that rsync can't deal with 
files that change while being copied, but the OS itself doesn't change 
when running and the logfiles, etc. that would change don't break 
anything if they aren't exactly the same in the copy.  Rsync wouldn't be 
a good choice to copy an active database, but it works fine for running 
programs.

-- 
   Les Mikesell
    lesmikesell at gmail.com