Disk cloning

翻譯狀態：

• 本文（或部分內容）是 Disk_cloning 的翻譯，最近一次同步的日期是 2014-08-04，如果英文版本有所更改，則您可以幫助同步翻譯更改的內容。
• 您可以在ArchWiki 的對應頁面找到本文翻譯的原始編輯記錄和貢獻者列表。

磁盤克隆是製作整個硬盤鏡像的過程, 其對於複製整個磁盤到別的電腦和備份/恢復都十分有用. 你可以訪問File recovery (簡體中文), 這是一個專注於文件恢復的頁面.

使用dd

dd命令是一個簡單而多功能且強大的工具. 它可以用於在無視文件系統或作業系統的情況下一塊一塊的將數據從原始地址複製到目的地. 在live環境比如livecd下使用dd是個方便的做法.

警告： 在使用這個工具時請對任何操作保持警惕, 因為它可以破壞你的數據. 請牢記輸入文件 (if=) 和输出文件 (of=) 的次序并千万不要颠倒他们! 请确保目的地(也就是分区 (of=) 不能小于源地址 (if=).

克隆分區

從物理盤 /dev/sda 的1分區 到物理盤 /dev/sdb 的1分區.

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

如果輸出文件 of (在這個例子中是sdb1) 不存在, dd 會從這個磁盤的開頭開始並且創建他.

克隆整個硬盤

從物理盤 /dev/sda 到物理盤 /dev/sdb

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

這條命令會克隆整個盤, 包括MBR(所以也包括bootloader), 所有的分區、UIUD 以及數據.

• notrunc (也就是'不許刪') 通過要求 dd 不對數據進行任何刪節來保證數據的統一完整.
• noerror 要求 dd 無視任何讀錯並繼續工作. dd的初始設定是一旦遇到錯誤就停下.
• sync 對讀錯誤進行清零, 這樣數據的開端就可以保持在 sync.
• bs=4096 將block size設置為4k. 這樣硬盤讀寫效率不知道高到哪裏去了, 顯然這個對克隆速度就是最好的.

注意： 如果想要重新獲得獨特的UUID, 請對每個分區都使用 "tune2fs /deb/sdbX -U random".

注意： dd帶來的分區表的改變並不會註冊到內核. 如果想要不重啟即傳達這一變化, 請使用類似於 partprobe(GNU parted 的一部分)的工具來達到目的.

備份MBR

MBR存儲在磁盤的前512位元組中。它由三部分組成：

1. 前446位元組包含引導加載程序。
2. 接下來的64個字節包含分區表（4個16位元組的條目，每個主分區一個條目）。
3. 最後2個字節包含一個標識符

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

創建磁盤映像

1. 從liveCD或liveUSB引導.

2. 確保沒有從源硬盤驅動器裝入分區.

3. 掛載外部硬盤

4. 備份硬盤.

 # 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

Examples with compression

When you need to create the hard drive or a single partition compressed backup image file you must use compression tools which can do backup from a stdout and the dd command. Those compressed files cannot be mounted by the mount command but are useful to know how to create and restore them.

7zip

Install the p7zip^包 package from the official repositories. This backup example will split the dd command output in the files by up to the 100 megabyte each:

dd if=/dev/sdXY | 7z a -v100m -t7z -si image-file.7z

Restore with 7zip:

7z x -so  image-file.7z | dd of=/dev/sdXY

注意： 7zip can split only the 7z compression type files

Zip

Install the zip^包 package from the official repositories, which contains zipsplit among other utilities for the management of zip archives. It will create a file with "-" name inside the image-file.zip file which will contain data from the dd command output. To make a raw output of the file you can use the -cp option with unzip in stdout for the dd command. Backup:

dd if=/dev/sdXY | zip --compression-method bzip2  image-file.zip - 

Restore:

unzip -cp image-file.zip | dd of=/dev/sdXY

The zip tool cannot split files on the fly but you can use the zipsplit utility on an already created file.

See also zip(1) for more information.

Rar

Install the rar^AUR package from the AUR.

警告： The rar examples were made based on the manuals, please confirm!

This should do a backup and split the creating file on the fly in by up to 150 megabyte files each.

dd if=/dev/sdXY | rar a -v150m -siimage-file.rar

This should restore

unrar x -p image-file.rar | dd of=/dev/sdXY

or you can use the rar instead of the unrar^包 utility. The unrar utility is available in the official repositories and can be installed with pacman -S unrar.

Bzip2

Creation by using the dd is more safe and use to be error free:

dd if=/dev/sdXY | bzip2 -f5 > compressedfile.bzip2

937016+0 records in
937016+0 records out
479752192 bytes (480 MB) copied, 94.7002 s, 5.1 MB/s

And a safe way of restoring with combination of the dd:

$ bunzip2 -dc compressedfile.bzip2 | dd of=/dev/sdXY

or

$ bzcat compressedfile.bzip2 | dd of=/dev/sdXY

警告： Never ever use the bzip2 -kdc imgage.bzip2 > /dev/sdXY and bzip2 -kc /dev/sdXY > imgage.bzip2 methods for serious backup of partitions and disks. The errors might be due the end of the device or partition and the restore process gives also errors due the truncated end.

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.

注意： This method should not be considered in the same category as disk cloning on the level at which dd operates. Also, it has been reported that even with the -a flag, some extended attributes may not be copied. For better results, rsync or tar should be used.

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 all attributes , 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)

Disk cloning software

Disk cloning in Arch

• Partclone provides utilities to save and restore used blocks on a partition and supports ext2, ext3, ext4, hfs+, reiserfs, reiser4, btrfs, vmfs3, vmfs5, xfs, jfs, ufs, ntfs, fat(12/16/32) and exfat. Optionally, a ncurses interface can be used. Partclone is available in the community repository.
• Partimage, an ncurses program, is available in the community repos. Partimage does not currently support ext4 or btrfs filesystems. NTFS is experimental.

Disk cloning outside of Arch

If you wish to backup or propagate your Arch install root, you are probably better off booting into something else and clone the partition from there. Some suggestions:

• PartedMagic has a very nice live cd/usb with PartImage and other recovery tools.
• Mindi is a linux distribution specifically for disk clone backup. It comes with its own cloning program, Mondo Rescue.
• Acronis True Image is a commercial disk cloner for Windows. It allows you to create a live (from within Windows), so you do not need a working Windows install on the actual machine to use it. After regitratinon of the Acronis software on their website, you will be able to download a Linux based Live cd and/or plugins for BartPE for creation of the Windows based live cd.
• 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.
• Redo Backup and Recovery is a Live CD featuring a graphical front-end to partclone.

外部連結

• Wikipedia:List of disk cloning software
• Arch Linux forum thread