On 4/23/20 11:10 AM, Rafael Skodlar wrote:
On 2020-04-23 07:56, R C wrote:
well, you can do it with dd, but the details are tricky at times.
You are not just "cloning" a disk, like you used to copy a disk. I
drive has multiple things, like an MBR, and
partitions and such. Most of the time to just clone a disk, copy it
if you will, works, but what one should really
do is copy partitions, figure out how big they need to be. And then
there's things like layout etc etc.
What clonezilla etc do, is use the same stuff, pretty much dd, except
they have some "logic" in their software on how
why mess with installing that when core utilities and a bit of bash
can do the same.
For system/Linux people that's easy to say. For others it's like
standing at the edge of a cliff and get the advise, well just don't
make another step. I don't think i works that way.
to copy those partitions, MBR/fat and all that. Some drives don't
care about alignment for example, and work not that
optimal, others might not work like that.
A "fail safe" way to do it is use sync or so. There are different
ways to do that though. If you do not want to "hammer"
the drive that is failing, you still create an img/iso, mount that
and then create a disk by partitioning/formating it, and after
that you use the mounted image with sync or so to move the files to
your new disk.
dd works really well for copying devices, especially if they are the
same or very similar, or for copying a device to a file/iso/img
or from an "image file" to a CD/DVD or SSD memory. Mostly used for
RapsberryPi and such.
dd is just a tool, very versatile and powerful, but as with all
tools, you need to know the details on how to use it and for what.
Bravo. I'm horrified reading recommendations to use dd for cloning
files on storage devices. dd copies fragmented files as is so you are
messing new drive for performance issues from the get go.
The best use for dd is in computer forensics and virtualization
environments for the same purpose or "deep troubleshooting" to find
out why a VM has issues.
I mentioned rsync to be one of the best and most effective utilities
for cloning locally or remotely in my experience. One option
"--dry-run" allows you to see what will happen without making a big
mistake if you are not careful.
There is another way to copy/clone files I learned in my Sun
OS/Solaris days.
Drive 1, /dev/sdb mounted /tmp/disk1
Drive 2, /dev/sdc mounted /tmp/disk2
(cd /tmp/disk1; tar cfp - *) | (cd /tmp/disk2; tar xvf -)
* assumes all directories but you can just name a few for the process.
tar utility was always on all Unix systems, rsync was not. There is
one more utility worth mentioning: cpio
You can change file ownership during file copy/clone process which is
some times necessary.
I miss days when utilities mt and rmt were needed for files
manipulation! It's magic to watch tape reels spin one way or the
other. No silly G-code needed to spin reels or have the drive suck
tape into vacuum chambers ;-)
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