hi guys, if i want to clone my server to an external hard drive and i type this command:
df -h

and it has this output:
File System Mounted on
/dev/sda3 /

so /dev/sda3 is the correct one to be the input for the dd command?

so if let's say my external drive is /dev/sda5

so my command will be: dd if=/dev/sda3 of=/dev/sda5

please help guys, whether that will be the correct method.

thanks for any help

server hard disk /dev/sdb external hard disk /dev/sda

bindas run this command it will clone it..

dd if=/dev/sdb of/dev/sda bs=4096

i created 10 times with this command ...have fun..

1 members found this post helpful.

With this you'll be copying one partition to another partition on the same disk. Run 'fdisk -l' as root to show you what disks and partitions are available to you. Also if the size of your target partition is smaller than your source partition then you may overwrite more than the target partition if there is another partition behind it instead of free space or the process may halt if it's the last partition on the disk without any free space left after it.
*The command centos123 showed you clones a whole disk. This may be easier if you've got two similarly sized disks and the target disk doesn't hold anything you'd want to keep anyway.

1 members found this post helpful.

unspan had wrote true...command i given is to clone whole disk.
but one thing you should remember your cloned disk will boot only in those pc whose configuration is same as source pc/server..

means you should have both machine hardware configuration same.else it will not boot or create issue or chance to get .corrupt ....

1 members found this post helpful.

I wonder but I think it's safer if you just copy the files with 'cp -a' with /dev/sda3 mounted somewhere as well other than root like /mnt/system. It probably defragments your files as well

1 members found this post helpful.

This I don't observe. If I:I will get at one point no space left. And the remaining partitions are still intact.

Well, since the sda3 partition was the root file system, a cp would (try to) copy some (logically) infinite files (/dev/null, /dev/zero, /dev/random, etc.) to the other partition. Unless you have an unlimited partition size, and can wait for the enegery death of the universe, this may not be a wise thing to do. Even a bind mount of an active root partition would, I believe, not help.

For the O.P., consider a Google of clonezilla.

If you just want a partition then you could even try things like gparted. Sda3 or such is a partition and not a clone of an OS as such.

Also partimage was used a lot. Clonezilla is as suggested a choice. +

Thanks for the correction.

The last time I did that (mounted in /mnt/system), I don't think it does. Perhaps if you do it with root where /dev is mounted, but not on /mnt/system.

Or maybe it doesn't always work. I did it a long time ago when I dup'ed my system to try building new packages.

Update: I just tried again and it does work. I tried copying the dev directory from there.