Re: [tlug] rsync vs dd [was Tlug Digest, Vol 14, Issue 23]

["Erin D. Hughes" <erin-hughes@??>]

Stephen J. Turnbull wrote:
>  > dd will copy the hd from one location to another exactly as is same size.
>
> However, I don't think this will work for CD or DVD; I doubt that dd
> can do all the work the mkisofs and cdrecord do.
>
>   
Sorry I wasn't clear about that. I *ass*u*me*d  he would copy the file 
to a hard drive or other device and then write the compressed file to a 
cd/dvd using the software of his choice, as you suggested below.

>  > I would also suggest not copying the proc/ folder because of the fact 
>  > that running process are there including your rsync process and it will 
>  > just keep copying the instance of itself till it eats up all your disc 
>  > space. So add  --exclude=/proc and you will be good.
>
> I don't think that's true.  rsync makes a list of files that need
> copying and copies each one, once. 
Unfortunately proven very true with disastrous consequences on Sol2.6 
and 8. On 2.6 the hard disc was already bad with no mirror and I wasted 
valuable time dicking around and the hard drive died in mid rsync after 
I had figured out what the problem was and excluded that directory.  But 
live and learn that is what backups are for.  Lucky I had one. On 8 I 
was just testing to see if it would happen again so I didn't really 
break anything. The result was a /tmp/proc folder over 8 gigs when I 
stopped it on 8.
>  Of course you don't want to copy
> /proc, but more because the data is volatile and read-only, and big
> (/proc/kcore, for example).  More important is that you don't want to
> copy something like /dev/random or /dev/zero, which never return EOF.
>   
Yes I forget about /dev my over site for not including that the first 
time around.
> I really think that rather than try to back up the whole hard drive in
> one shot, you should back up /etc, /home, /var, and maybe /usr/local
> and /boot.  /var should contain your pms state, so you don't really
> need /usr, /bin, or /sbin.  /proc and /dev you shouldn't touch for the
> reasons above.
>   
> If you really want to use dd, I would recommend partitioning the HDD
> and using dd to write the partitions to files, which can be compressed
> and burned to DVD.
>   
I think it would be helpful if we knew what the end goal was here.

Are we trying to replace the existing hard disc so it can be swapped 
with a larger one and restored on to the new drive keeping the same OS 
and settings or do you just want to a exact copy of your hard drive for 
backup purposes?

E./

--
Erin D. Hughes