Disk cloning (Italiano)

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La clonazione del disco è il processo di creare un'immagine di una partizione o di un intero disco rigido. Ciò può tornare utile sia per copiare il disco su un altro computer, sia per finalità di backup\recupero dei dati.

Usando dd

Il comando Template:Codeline è un semplice, versatile e potente strumento. Può essere usato per copiare dalla sorgente alla destinazione, blocco per blocco, a prescindere dal tipo di filesystem oppure dal sistema operativo. Un metodo più conveniente è quello di usare Template:Codeline da un ambiente live, come un livecd.

Attenzione: Data la natura di questi comandi, è bene essere molto cauti nel loro utilizzo; questi comandi possono distruggere i vostri dati. Ricordare che l'ordine è file di input (if=) e file di output (of=) e non invertiteli! Assicurarsi sempre che il disco/partizione di destinazione (of=) sia uguale o più grande dell'origine (if=).

Cloning a partition

From physical disk /dev/sda, partition 1, to physical disk /dev/sdb, partition 1.

dd if=/dev/sda1 of=/dev/sdb1 bs=4096 conv=notrunc,noerror

If output file of (sdb1 in the example) does not exist, dd will start at the beginning of the disk and create it.

Cloning an entire hard disk

From physical disk /dev/sda to physical disk /dev/sdb

dd if=/dev/sda of=/dev/sdb bs=4096 conv=notrunc,noerror

This will clone the entire drive, including MBR (and therefore bootloader), all partitions and data.

  • notrunc or 'do not truncate' maintains data integrity by instructing dd not to truncate any data.
  • noerror instructs dd to continue operation, ignoring all input errors. Default behavior for dd is to halt at any error.
  • bs=4096 sets the block size to 4k, an optimal size for hard disk read/write efficiency and therefore, cloning speed.

Backing up the MBR

The MBR is stored in the the first 512 bytes of the disk. It consist of 3 parts:

  1. The first 446 bytes contain the boot loader.
  2. The next 64 bytes contain the partition table (4 entries of 16 bytes each, one entry for each primary partition).
  3. The last 2 bytes contain an identifier

To save the MBR into the file "mbr.img":

  # dd if=/dev/hda of=/mnt/sda1/mbr.img bs=512 count=1

To restore (be careful : this could destroy your existing partition table and with it access to all data on the disk):

  # dd if=/mnt/sda1/mbr.img of=/dev/hda

If you only want to restore the boot loader, but not the primary partition table entries, just restore the first 446 bytes of the MBR:

  # dd if=/mnt/sda1/mbr.img of=/dev/hda bs=446 count=1

To restore only the partition table, one must use

  # dd if=/mnt/sda1/mbr.img of=/dev/hda bs=1 skip=446 count=64

You can also get the MBR from a full dd disk image.

  #dd if=/path/to/disk.img of=/mnt/sda1/mbr.img bs=512 count=1

Create disk image

1. Boot from a liveCD or liveUSB.

2. Make sure no partitions are mounted from the source hard drive.

3. Mount the external HD

4. Backup the drive.

 # dd if=/dev/hda conv=sync,noerror bs=64K | gzip -c  > /mnt/sda1/hda.img.gz

5. Save extra information about the drive geometry necessary in order to interpret the partition table stored within the image. The most important of which is the cylinder size.

 # fdisk -l /dev/hda > /mnt/sda1/hda_fdisk.info

NOTE: You may wish to use a block size (bs=) that is equal to the amount of cache on the HD you are backing up. For example, bs=8192K works for an 8MB cache. The 64K mentioned in this article is better than the default bs=512 bytes, but it will run faster with a larger bs=.

Restore system

To restore your system:

 # gunzip -c /mnt/sda1/hda.img.gz | dd of=/dev/hda

Using cp

The cp program can be used to clone a disk, one partition at a time. An advantage to using cp is that the filesystem type of the destination partition(s) may be the same or different than the source. For safety, perform the process from a live environment.

The basic procedure from a live environment will be:

  • Create the new destination partition(s) (using fdisk, cfdisk or other tools available in the live environment.
  • Create a filesystem on each of the newly created partitions. Example:
mkfs -t ext3 /dev/sdb1
  • Mount the source and destination partitions. Example:
mount -t ext3 /dev/sda1 /mnt/source
mount -t ext3 /dev/sdb1 /mnt/destination
  • Copy the files from the source partition to the destination
cp -a /mnt/source/* /mnt/destination

-a: preserve permissions, never follow symbolic links and copy recursively

  • Change the mount points of the newly cloned partitions in /etc/fstab accordingly
  • Finally, install the GRUB bootloader if necessary. (See GRUB)

Software per la clonazione del disco

Clonazione del disco in Arch

Il programma ncurses PartImage è nel repository community. La sua interfaccia non è eccezionalmente intuitiva, ma funziona. Non ci sono attualmente programmi di clonazione con interfaccia grafica GTK\QT per Linux. Un'altra opzione è quella di utilizzare il comando Template:Codeline, una piccola utility per creare file immagine. Wikipedia ha una lista delle varie versioni di dd, specificatamente orientate a questo tipo di scopo. [1]. dd_rescue works efficiently with corrupt disks copying error free areas first and later retrying error areas.


Clonazione del disco all'infuori di Arch

Se desiderate fare un backup o installare in serie la vostra installazione-tipo di Arch, probabilmente fareste meglio ad usare un altro pc e clonare il disco da li. Alcuni suggerimenti:


  • PartedMagic ha un bel live cd/usb con PartImage ed altri strumenti per il recupero dati.
  • Mindi è una distribuzione Linux specifica per fare delle clonazioni backup dei dischi. È fornita insieme al suo programma specifico, Mondo Rescue.
  • Acronis True Image è un programma commerciale per Windows. Permette di creare un live cd (da Windows), cosicchè non avrete necessità di installare Windows sulla macchina che volete clonare per utilizzarlo.
  • FSArchiver allows you to save the contents of a file system to a compressed archive file. Can be found on the System Rescue CD.
  • Clonezilla is an enhanced partition imager which can also restore entire disks as well as partitions.

External Links