Linux ddコマンド詳細説明：データのバックアップ、およびバックアッププロセスでのフォーマット変換のケース

[root@localhost ~]# dd if="input file" of="output file" bs="data block" count="number"

[root@localhost ~]# dd if=/etc/httpd/conf/httpd.conf of=/tmp/httpd.bak
Recorded 67+1 reads in
# data accounts for 67 blocks of writes and 1 block of unwritten data
Recorded 67+1 writes out
#Default data block size is 512 bytes
34439 bytes (34 kB) copied, 0.0524897 seconds, 656 kB/sec
#If you want to backup files, then the dd command is very similar to the cp command
[root@localhost ~]# ll -h /tmp/httpd.bak
-rw-r--r--.1 root root 34K Jun 5 18:04 /tmp/httpd.bak
# check the size of the generated backup file

[root@localhost ~]# df -h
File System Capacity Used Available Used %% Mount Point
/dev/sda3 20G 2.0G 17G 11% /
tmpfs 306M 0 306M 0% /dev/shm
/dev/sda1 194M 27M 157M 15% /boot
/dev/sr0 3.5G 3.5G 0 100% /mnt/cdrom
#To check the partition capacity, we backup the /boot partition
[root@localhost ~]# dd if=/dev/sda1 of=/tmp/boot.bak
# backup completed
[root@localhost ~]# ll -h /tmp/boot.bak
-rw-r--r--.1 root root 200M June 5 18:14 /tmp/boot.bak
#View the generated backup file
# If you need to restore, then execute the following command
[root@localhost ~]# dd if=/tmp/boot.bak of=/dev/sda1

[root@localhost ~]# dd if=/dev/sda1 of=/dev/sdb1
# If you need to restore, simply reverse the input and output entries with the following command
[root@localhost ~]# dd if=/dev/sdb1 of=/dev/sda1

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[root@localhost ~]# dd if=/dev/sda of=/dev/sdb
# back up disk a to disk b
[root@localhost ~]# dd if=/dev/sda of=/tmp/disk.bak
# back up disk a to the file disk.bak
#backup restore
# If you want to back up to another drive, then simply replace the source drive with the backup drive when the source drive data is corrupted
#If you want to backup to a file, then you need to copy the backup data to another Linux during recovery, and then install the new hard disk to this Linux
# Server, then copy the disk backup data to the new hard disk. The command is as follows
[root@localhost ~]# dd if=/tmp/disk.bak of=/dev/sdb

[root@localhost ~]# dd if=/dev/fd0 of=/tmp/fd.bak
# In Linux, the device file name of a floppy disk is /dev/fd0
#This command first saves the data on the floppy disk as a temporary data file
[root@localhost ~]# dd if=/tmp/fd.bak of=/dev/fd0
# then replace the floppy with a new one and copy the data backup to the new floppy to achieve the floppy copy