hey guys, I understand how dd works. Ive been researching on it and I see that
if="" is the source of what I want to copy
of="" is that target that I want to send the back up to

so, what i am trying to do it copy my hard drive from saturn server: /dev/sda1 over SSH to my backup server skyline.

so [saturn harddrive /dev/sda1] -----backup---> [skyline:/backup/directory]


this is the command I am using
sudo ssh willc86@skyline "dd if=/dev/sda1 " | dd of=/backup/saturn.img

however, it is saying failed to open /dev/sda1/ : permission denied and I am runnign as root. any idea why?

thanks a bunch guys!

Ok. So you have the basics. Your point of confusion is in the interaction with ssh. Secure shell connects that terminal session to another terminal, in your case, a terminal on your saturn server. Within SSH you are no longer sending commands to your local computer, so /dev/sda1 will actually point to the saturn server's drive.

I recommend that you familiarize yourself with scp, secure copy. SCP uses a secure shell connection to another terminal for the explicit purpose of copying data from one system to another.

I also recommend you read a bit more on dd. A better dd command will look more like
<code>dd if=/dev/sda1 of=/some/other/device</code>
Good luck and let us know if this helped.

By the way, kudos for actually posting the command that you need help with. You're already a step ahead of the game.

Nope.
You are running it as willc86 on skyline and it is attempting to read /dev/sda1 on skyline.

Probably you want to mount the destination locally and then run your dd command.

This command of yours only puts a image of sda1 in your remote server storage space only. So first make a sda1 image. And then use scp or better rsync to transfer file.

Oh. Woops! Thanks descendant_command. I guess my brain just skipped right over the username and servername. My bad.

I agree with the suggestion of mounting the remote destination locally. That will make the dd command much simpler.

It isn't obvious which server you are running the command from. What you posted would work if you were running from skyline and if you ssh into Saturn as root.

As stated there are several ways to accomplish the same thing which may be easier.

i am doing this command from skyline

anyhow, i think I am going to transfer it over from the same drive over
prior to doing dd command, is there anything else I need to do? exclude /proc or dd takes care of everything on the spot? and its really that easy

In the thread title you state "backing up a Linux OS". DD is not the correct tool for backup. Its a tools for drive imaging or drive cloning whatever you call it. It makes a bit-by-bit copy of your disk.

Are you sure that is what you want? Usually a backup is on file level. Not on bit level. Especially because you want to do your backup over SSH, it is unlikely you want that image. Other utilities for copying on the file level like rsync come to mind.

jlinkels

urgh ok I am getting a bit confused lol sorry.

what is the correct way to back up your system, then restore it back if a configuration goes wrong. DD command is not a good way? I would like to back up the entire drive; or should I just use clonezilla


actually - i see why. I noticed dd copys the entire drive, even the blank spaces =/

There are many backup options in Linux. Rsync serves me well. It backs up every file. But it does not create a bootable image. That means after a full crash you have to install a minimum system and then rsync all files back to restore the original system state.

jlinkels

Which backup package to use depends on your needs. Rsync, tar, dd, and many others will do the job, but it depends on what the job really is. If you want to be able to just take the backup and use it to make a bootable drive on a new HDD, then dd may be what you want. If you just want to restore the backup to a working bootable drive, it probably isn't. Only you know exactly what you want or need. Different people have different needs, and that's why there are many options available.

<soapbox>
dd is never the correct option for backup. Unless you're doing forensics.
</soapbox>

There are uncounted options for backup - some have been mentioned in this thread. As usual the Arch doco is exemplary - have a look over this synopsis.