What does dd image mean. System backup
The dd command does just one simple thing: it copies data from a file to another file. But since in Linux many entities are represented exactly as files, then dd has many uses. Let's consider the most useful of them.
What does dd mean?
dd is short for data duplicator (copying data). But due to the fact that in the wrong hands the dd command can lead to the complete loss of all data, the program is often jokingly called disk destroyer (disk destroyer). Let's try to figure out how not only not to destroy our data, but even to benefit from the use of dd.
General use case for dd
The command syntax is as follows:
Dd if=$input_data of=$output_data
The command will copy the data from the $input_data file to the $output_data file, given the option options. It would seem that everything is simple. Now consider what opportunities this simple copying opens up.
Examples of using dd
1. Destruction of all data on the disk without the possibility of recovery:
Dd if=/dev/urandom of=/dev/sda bs=4k
2. Full byte-by-byte copying of one disk to another (cloning):
Dd if=/dev/sda of=/dev/sdb bs=4096
3. Copying one section to another:
Dd if=/dev/sda3 of=/dev/sdb3 bs=4096 conv=notrunc,noerror
4. Displaying the list of available file systems:
Dd if=/proc/filesystems | hexdump -C | less
5. Copying data on devices with different block sizes (1Kb for the source and 2Kb for the destination):
Dd if=/dev/st0 ibs=1024 obs=2048 of=/dev/st1
6. Create a bootable flash drive:
Dd if=/home/$user/bootimage.img of=/dev/sdc
7. Check the disk for bad sectors:
Dd if=/dev/sda of=/dev/null bs=1m
8. Create a backup copy of the MBR disk and save to a floppy disk
Dd if=/dev/sda of=/dev/fd0 bs=512 count=1
9. Removing the ISO image from the CD:
Dd if=/dev/sr0 of=/home/$user/mycdimage.iso bs=2048 conv=nosync
10. Checking the file for viruses (of course, ClamAV will be required):
Dd if=/home/$user/suspicious.doc | clamscan-
11. Saving the contents of RAM to a file:
Dd if=/dev/mem of=/home/$user/mem.bin bs=1024
12. Convert image from Nero NRG format to standard ISO image:
Dd bs=1k if=imagefile.nrg of=imagefile.iso skip=300k
13.View MBR content:
Dd if=/dev/sda count=1 | hexdump -C
And where is the promised million applications?
The observant reader will probably notice that the article does not list a million useful applications, but a few less. But the power of the dd program lies in the fact that the user can find other uses on his own by combining different files as if, of parameters and selecting the necessary options. Just remember that working with dd requires extra attention. If you do not know exactly what actions will be performed, then it is better to refrain from experimenting. Try not to give dd superuser rights when you can do without these rights.
Your own examples of using this wonderful program are welcome in the comments.
I decided the other day to create an image of my working, bootable flash drives with different operating systems. How to create these multi-boot flash drives, I already in one of his articles. Will help us, in creating images, an old and time-tested program dd. As far as I know, the dd utility should be installed on the system by default. To create an image of your "flash drive", run the following command in the Terminal:
sudo dd if=/dev/sdc of=image.iso
/dev/sdc is your flash drive
image.iso is an image named image and expansion .iso, which will appear in your home folder.
To find out how your flash drive is designated in the system, for example, you can run the Disks utility, or the GParted program and look in them, and if through the Terminal, the command will help:
sudo fdisk -l
If you want to see the process of creating a flash drive, then there are several ways. I will not tell the first way, because I did not like it, but the alternative solution to this problem looks much better. To do this, you will need to install an improved version of dd, which is called dcfldd.
sudo apt-get install dcfldd
The staff of the DoD Computer Forensics Laboratory (DCFL) made some changes to the dd command, thereby improving it and using it in their research work. As a result, the dcfldd command was born, which provides hashing of the copied data at certain intervals for their authentication. Moreover, dcfldd is much faster than dd. Now, if you want to see the progress of copying or creating an image, you need to run the command:
sudo dcfldd if=/dev/sdc of=image.iso
Now that the image is ready, you can create a new, bootable USB flash drive. Instead of a flash drive with systems, we will insert a new, empty one. I think that it will be determined by the system in the same way as the first one - sdc, but it's better to double-check. Now the command will be like this:
sudo dd if=image.iso of=/dev/sdc
Well, if your empty flash drive has the same size as the media with the data you need, then you can simply copy the entire contents of the first flash drive immediately to the second one, bypassing the creation of an image on your hard drive. In this case, the command would be:
sudo dd if=/dev/sdb of=/dev/sdc
According to this scheme, you can copy, create images not only of flash drives, but also of entire hard drives, or their partitions, CD / DVD drives, etc. But more on that in the next article.
The choice of flash drives is up to you. You can burn a bootable image to ordinary flash drives from well-known brands: Transcend, Kingston, Apacer, Silicon Power and other manufacturers, or you can differ a little and choose jewelry flash drives with rhinestones, diamonds and other decorations. Although this of course will be the choice of the beautiful half of humanity. While at work, the recorded image, appearance The device is not affected at all.
dd- a simple utility that is included with most Unix-like operating systems - Linux, FreeBSD, Solaris, etc.
Its purpose is to read data from one device or file and write to another.
dd can be effectively used to create an image hard drive, while doing without commercial utilities like Acronis True Image or Norton Ghost.
Let's assume we have two disks:
- /dev/sda is the disk to be imaged;
- /dev/sdb is the disk where the image will be written to.
Substitute your own values if necessary.
The first step is to boot from any available Live-CD that has the dd utility and enter command line as superuser. Create a mount point for backup.
mkdir /mnt/backup
Mount the hard drive on which you want to save the image.
Create a hard drive image
dd if=/dev/sda of=/mnt/backup/sda.img bs=8M conv=sync,noerror
- if=/dev/sda - copy the entire hard disk sda;
- of=/mnt/backup/sda.img - copy to /mnt/backup/sda.img;
- bs=8M - set the size of the hard disk cache to speed up the copy procedure (otherwise the data will be dumped in small portions of 512 bytes);
- conv=sync,noerror - tell dd to copy bit-for-bit, ignoring read errors.
To reduce the size of a hard disk image, you can compress it with any archiver.
dd if=/dev/sda bs=8M conv=sync,noerror | gzip -c > /mnt/backup/sda.img
Restoring a hard drive image
To restore a hard disk image, you need to follow the procedure reverse to the procedure for creating this image.
dd if=/mnt/backup/sda.img of=/dev/sda bs=8M conv=sync,noerror
When using compression in parallel, you must unzip the image.
gunzip -c /mnt/backup/sda.img | dd of=/dev/sda conv=sync,noerror bs=8M
Migrating the system to another hard drive
To migrate the entire system to another hard drive, you must set the destination of the new drive as the destination.
dd if=/dev/sda of=/dev/sdb bs=8M conv=sync,noerror
Then, if necessary, install the boot from this hard drive. Provided that the new hard drive is larger than the old one, it will remain unallocated area. It should be marked and formatted according to existing requirements.
Copy statistics in dd
The main disadvantage in dd is the lack of a visual representation of the statistics of the execution of the copy procedure. However, this disadvantage can be easily circumvented. It is enough to connect to another terminal.
Determine the process number under which dd is running.
Periodically send this process a kill -USR1 dd_process_number command.
watch -n 5 kill -USR1 dd_process_number
- watch -n 5 - run the command every 5 seconds;
- kill -USR1 dd_process_number - show copy statistics.
Cons of using dd to create disk images
Everything has pros and cons. dd is a free and very flexible tool, but it can only do a full copy of a volume. Special programs can copy only the data that is stored on the disk.
Thus, the volume of a disk image created with dd will be equal to the volume of the disk itself - regardless of how much data is on the disk.
As is known, "computer users are divided into those who make backups and those who will do them". In this article, we will look at various ways to back up (backup) the entire system and, accordingly, restore from a backup.
It should be noted right away that all operations should not be carried out “live”, i.e. not on a running system, but from a liveCD or system installed on an adjacent partition / flash drive / usb-hdd. In cases where a downtime of a few minutes is critical for the system, it is possible to copy the system from under itself, but some additional conditions must be taken into account, which are not yet considered in this article.
From now on, for actions performed as root, the sudo command will be used, which is the standard for Ubuntu. On other systems it is possible to gain superuser privileges via su , some liveCD systems run in superuser mode by default
tar
One of the most popular ways to create a simple backup is to archive data using tar . The advantages of this method are the possibility of incremental backup (adding files to an existing archive, deleting or changing them), the ability to extract individual files from the archive, as well as the presence of tar on almost any Linux system.
Creating an archive
First, create mount points for the root partition and for the partition on which you are going to create a backup, like this
Mount both partitions. For greater reliability, you can mount the root partition in read-only mode (read-only) to eliminate the possibility of accidental data changes
sudo mount /dev/sdXY /mnt/root -o ro sudo mount /dev/sdXY /mnt/backup
(Instead of "sdXY" use your values for the desired partitions. You can determine them with sudo fdisk -l or sudo blkid)
In case you use separate partitions for /boot, /usr, /home, etc. and want to include their contents in the backup, mount them in the appropriate folders
sudo mount /dev/sdXY /mnt/root/usr -o ro sudo mount /dev/sdXY /mnt/root/home -o ro
If necessary, create a folder on the backup partition where you want to place the archive, for example
sudo mkdir -p /mnt/backup/ubuntu/root
Now you can start creating the archive. To create a gzip compressed archive, run
Sudo tar -cvzpf -C /mnt/root /mnt/backup/ubuntu-sda1.tar.gz .
(The -p switch enables saving owners and permissions for files)
For bzip2 compression use
Sudo tar -cvjpf /mnt/backup/ubuntu-sda1.tar.bz2 /mnt/root
For lzma compression
sudo tar --lzma -cvpf /mnt/backup/ubuntu-sda1.tar.lzma /mnt/root
Similarly for lzo compression - switch --lzop instead of --lzma
Different compression algorithms give different archive sizes and also differ in performance.
At the end of the process, unmount all mounted partitions
Sudo umount /mnt/root(/boot,/var,/home,) /mnt/backup
Restoring from an archive
Create mount points for the root partition and the partition where your archive is stored
Sudo mkdir /mnt/(root,backup)
Mount the backup partition
sudo mount /dev/sdXY /mnt/backup -o ro
Format the root partition to the same (or different) FS. If you are using separate partitions for /usr, /boot, etc. and have archived them, format them too
(if you are restoring to a new hard drive, partition it with fdisk/gparted and format the partitions)
Some file systems support setting a UUID when formatting. This makes it possible to create a file system with the same UUID as the old one, which will avoid the need to edit fstab .
For ext2/3/4, the UUID is set using the -U switch, and you can simplify the task even more with a command like
sudo mkfs.ext4 -L "label" -U "$(sudo blkid -o value -s UUID /dev/sda1)" /dev/sda1
If you used archiving when creating the image file, first unpack it using the same archiver, for example
Bzip2 -dv /media/backup/sda5.dd.bz
Now you can mount the image
sudo mount /media/backup/sda5.dd -o loop /mnt
(With the loop option, the mount program will automatically "hook up" the image file to a free loop device, and then mount the file system)
Now you can work with the contents of the image as with a regular file system, all your changes will be written to the image. When finished, unmount the image as a regular FS
sudo umount /mnt
dd - copy the entire hard drive
In this case, we will use dd again, only this time we will save the entire contents of the hard disk - with the partition table, the partitions themselves, and all the data. The advantage of this method is that you can save all the systems installed on this hard drive in one step without having to back up each partition separately. In addition, with such a backup, all data related to the bootloader will be saved - thus, after restoring from a backup, you will not need additional manipulations, you can immediately boot from this hard drive.
Creating an image
In general, the procedure is similar to that described above for backing up individual partitions. In this case, the advice about clearing free space with “zeros” is also applicable - if you have free time, do this with all sections.
Before starting the operation, make sure that none of the partitions of this hard disk is mounted. You can do this by running the mount command with no options.
Select the partition where you are going to place the obarz file. Of course, this must be a partition of another hard drive. Also make sure that there is enough free space on this partition (for example, using the df utility) - the amount of free space should correspond to the size of the copied hard disk (when compressed, the image will be smaller, but this depends on the type of data stored).
Mount the backup partition
sudo mount /dev/sdXY /mnt
Now you can start
sudo dd if=/dev/sdX bs=1M conv=noerror,sync | lzma -cv > /mnt/hdd.dd.lzma
(here "sdX" is a disk, not a partition! for copying without compression, the command is similar to the one above for a partition backup)
Depending on the size of the hard drive and the performance of your computer, the procedure may take a long time (up to several hours). When done, unmount the backup partition
sudo umount /mnt
Restoring from an image
Attention! This method involves a complete rollback to the state at the time of creating the archive with the replacement of all data!
Before starting work, make sure the power supply is reliable. Connect the AC adapter if you have a laptop, and use a UPS or stabilizer if possible. High write intensity increases the risk of disk damage in the event of a power failure
Make sure that no partition of the disk being restored is in use. Mount the backup partition
sudo mount /dev/sdXY /mnt
You can start the process
Bzip2 -dc /mnt/hdd.dd.bz | sudo dd of=/dev/sdX bs=1M conv=sync,noerror
Or for an uncompressed image
sudo dd if=/mnt/hdd.dd.bz of=/dev/sdX bs=1M conv=sync,noerror
When done, unmount the backup partition
sudo umount /mnt
If you want to extract the image to another hard drive, it must be at least as large as the original. If new disk larger, you can extend partitions or create a new partition from free space with parted/fdisk/gparted/etc
Do not use both hard drives ("duplicate" and "original") at the same time! If both drives are connected, the system will have two partitions for each UUID, which will lead to problems in operation or inability to boot
Mounting the image
By analogy with a partition image, you can work with a hard disk image just like a normal hard disk. In this case, the procedure is somewhat more complicated, since the image contains several sections.
If the image is compressed, unpack it. Now "hook" the image to the loop device
sudo losetup -fv /media/backup/sda.dd
(With the -f switch, the program will automatically find a free loop device, otherwise you must explicitly specify it)
losetup will display the name of the used device - unless you are working with other image files (iso, encrypted containers, etc.), it will most likely be /dev/loop0
Now we have a device that is a hard disk for the system, but we do not have access to its partitions. The kpartx program will help you get to the partitions (you may need to install the package of the same name)
sudo kpartx -av /dev/loop0
(Switch -a - add partitions for the specified device; -v - informative output)
The program will display the names of the created devices for the disk partitions: loop0p1 for the first partition, loop0p2 - for the second, by analogy with the partitions of a regular disk. Device files will be in the /dev/mapper folder
Now you can work with partitions and FS on them. For example, mount the former sda5 and write files to it
sudo mount /dev/mapper/loop0p5 /mnt
When done, unmount the partition
sudo umount /mnt
Remove partition devices with kpartx
sudo kpartx -dv /dev/loop0
and release the loop device
sudo losetup -v -d /dev/loop0
All! The changes have been written, and your image has become a regular file again.
cp
Here we will consider a backup using the cp utility, i.e. using simple copy. Actually, this is not the best way, and it is more suitable for copying the system to another hard disk / partition / computer, rather than creating a backup.
On the other hand, this method has several advantages:
Versatility - cp can be found on any Linux system
Low resource requirements (due to the lack of compression and the simplicity of the mechanism)
Ease of further work with the backup (adding / changing / deleting files, extracting the necessary data, etc.)
Making a copy
Create mount points for root and backup partitions
Sudo mkdir /mnt/(root,backup)
Mount both partitions
sudo mount /dev/sdXY -o ro /mnt/root sudo mount /dev/sdXY /mnt/backup
Mount partitions for /usr, /boot, etc., if any
sudo mount /dev/sdXY -o ro /mnt/root/home
Create a folder on the backup partition for your backup
Sudo mkdir /mnt/backup/ubuntu
You can start
sudo cp -av /mnt/root/* /mnt/backup/ubuntu
(the -a switch enables copying links "as is", saving all possible file attributes and recursive mode. the -v switch - output information about what is happening)
At the end of the process, unmount all partitions
In the future, you can archive your data in any convenient way.
Restoring from a copy
Attention! This method involves a complete rollback to the state at the time of creating the archive with the replacement of all data!
Create mount points for partitions
Sudo mkdir /mnt/(root,backup)
Mount the backup partition
sudo mount /dev/sdXY -o ro /mnt/backup
Format the root partition and partitions /usr, /boot, etc., if any. (For formatting partitions with saving UUID, see the section about)
sudo mkfs.reiserfs -l "root" /dev/sdXY sudo mkfs.ext2 -L "boot" /dev/sdXY sudo mkfs.ext4 -L "home" /dev/sdXY
Mount the newly created FS
The process of copying is similar, only in the opposite direction.
sudo cp /mnt/backup/ubuntu/* -av /mnt/root
Once the copy is complete, edit fstab to correct the UUID of the partitions
Unmount partitions
sudo umount /mnt/backup /mnt/root/(usr,home,)
squashfs
sudo mkfs.reiserfs -l "root" /dev/sdXY sudo mkfs.ext2 -L "boot" /dev/sdXY sudo mkfs.ext4 -L "home" /dev/sdXYMount the newly created FS
sudo mount /dev/sdXY /mnt/root sudo mount /dev/sdXY /mnt/root/usr sudo mount /dev/sdXY /mnt/root/var
You can start! The unsquashfs utility is used to unpack the image.
sudo unsquashfs -d /mnt/root -f /mnt/backup/ubuntu-root.sqfs
(The -d key specifies the path for unpacking; with the -f key, the program will use existing folders instead of trying to create new ones)
As with image creation, you'll see a progress bar and lots of other useful information.
When finished, edit fstab to replace the UUIDs of the partitions with the new ones (if you formatted partitions with the same UUIDs, skip this step)
Sudo nano /mnt/root/etc/fstab
Save the file and unmount all partitions
sudo umount /mnt/backup /mnt/root(/usr,/var,)
Mounting the image
squashfs is mounted like any other image - via a loop device. Kernel support for squashfs is included in many distributions, including Ubuntu, so it will be enough just to use the mount command with the loop option
sudo mount /media/backup/ubuntu-root.sqfs -o ro,loop /mnt
(The ro option is not required, because writing there still won't work)
Now you can copy any desired files from the image. Adding something in this way will not work, for this you will need to use mksquashfs again
When finished, unmount the image as a normal filesystem
sudo umount /mnt
rsync
Like cp , rsync operates on files, not block devices. The peculiarity of rsync is that it does not copy files that are already on the destination. By default, it checks the size and modification time of files, but you can also check the hash (usually this is done when increased security is needed).
Easy use
The syntax for rsync is similar to cp:
Rsync -a /mnt/root /mnt/backup
The -a option is very often enough, it provides the most necessary: recursive copying of directories, saving owner and group information, etc. To display detailed information about copying, the -v switch is used, be careful with it, you can skip the error message in the data stream. The -x switch ensures that rsync will not go beyond the specified filesystem.
The documentation for rsync describes a lot of options. For example, there are some that allow you to copy over SSH, or remove a file from the destination if it was deleted in the source directory.
"Smart" copying reduces system downtime. We run rsync directly on a running system, the data in which is constantly changing, rsync copies the data, say, for several hours. Then we put the system in read-only, run rsync again, now it copies only those files that have changed in these few hours. In a few minutes we have a complete copy of the original FS. At the same time, downtime was reduced by an order of magnitude compared to offline copying. And in some cases, one online copy will be enough without transferring the system to read-only.
Keeping Previous Copies
Strictly speaking, rsync is not a backup tool - it is a synchronization tool. This is important when making regular backups, because if any important file is deleted in the working directory of the source, rsync will delete it in the backup as well. To increase the safety of data, it is advisable to keep old backups. However, simply saving multiple copies will require a lot of hard disk space. If copies have many of the same files, then this leads to unnecessary redundancy. This problem can be solved by using hard links.
The bottom line is that in modern file systems (including Ext4) file addressing is performed in two stages: the file name points to a unique file number (index descriptor or i-node), and the data itself is associated with this number. Any filename is, in fact, a hard link to that number. Consequently, a file (data set) can have several names and be in different directories, and this allows you to eliminate redundancy if you need to duplicate files (after all, a hard link takes up little memory). The data itself is not deleted until the removal of the last hard link is requested.
A significant limitation is that hard links are only possible within the same file system.
Synchronizing the contents of the directory for the current backup with the source directory:
rsync \ --archive \ --delete --delete-excluded \ # remove from the backup non-existent in the source and excluded files--progress \ # print information about transfer progress"/home/user/Files/" \ # source directory"/backup/latest/" \ # directory for current backup--exclude="/Public/" # exclude unnecessary directories
In the /backup/latest/ directory, a copy of all the necessary files and directories from the source will be created and everything unnecessary will be removed.
Create another current backup without redundancy:
cp\ --archive\ # save all additional information about files--link \ # use hard links for files - eliminating redundancy"/backup/latest/" \ # source is the current backup obtained above "/backup/$(date +%Y-%m-%d_%H-%M-%S) /" # destination is a directory with the date in the name for convenience (see man date)The next time a backup is created, rsync will delete files in the /backup/latest/ directory that have been deleted/excluded/modified in the source directory (changed files are first deleted and then written to a new version). However, only the names of the files (the same hard links) will be deleted, the files themselves (data) are saved, since hard links were created on them in the neighboring directory with the “cp” command.
Other tools
There are many applications for creating backups in Linux. You can search for "backup" in the Ubuntu Software Center to find backup software available in Ubuntu.
For a corporate environment and just for fairly large-scale and critical backup tasks, we can recommend understanding one of the most popular and powerful backup systems for Linux called Bacula
By the way, you can also find Russian-language manuals on the net.
Parted Magic
Parted Magic is another great one, but paid a distribution kit containing a whole collection of tools for backing up and restoring information, working with disks and partitions, as well as recovering lost data. It supports many file systems, LVM2 and RAID (both hardware and software) and contains such tools as fsarchiver , GParted , Clonezilla mentioned above, and everything that is required for the methods described in this article. In addition, the distribution kit includes a web browser and some other additional software. The distribution kit is translated into several languages, including Russian, and has a full-fledged graphical interface.
LParted
LParted is a full-featured LiveCD designed primarily for working with hard disk (HDD) partitions, permanently deleting or restoring data, and testing equipment. LiveCD based on Lubuntu Linux. LParted is a functional analogue of Parted Magic.
Here I would add about SystemRescueCD and others
More about saving data
For important data, you can make a mirror partition on two disks. To do this, it is not necessary to have a RAID controller and disks of the same size - you can, for example, assemble a mirror from an 80 GB old screw and an 80 GB partition on a new one. Mirroring can be implemented using LVM or software RAID. However, this method is useless in case, for example, ~220V voltage hits the +5V bus or a meteorite falls on the computer system unit.
IT geeks who have their own server at home can extend the idea of mirroring and use DRBD. The same RAID-1, but the hard drives are in different computers, which increases reliability.
A modern convenient solution is to back up data to the "clouds", for example, using Ubuntu One, Dropbox, http://www.adrive.com/ and others.
Neither mirroring nor replication on Ubuntu One will save you from accidentally pressing Delete, so make “classic” backups anyway. And one fine terrible day, all your labors and efforts will be rewarded.
Rufus- free software open source code for formatting removable USB storage media and creating bootable drives with various operating systems. The program is easy to use, high speed and supports a multilingual interface.
You can download the program on the developer's website. The page contains links to download the standard version Rufus, and portable Rufus portable, which do not differ in anything, except for the name of the executable file and the location where the settings are stored. The program settings include the language used and the settings for checking for updates. The standard version stores these settings in the registry, while the portable version stores them in a file rufus.ini program directory. Rufus does not require installation on the system - just download the executable file and run it. The program interface is very simple:
In general, the program Rufus is not something unique in the field of tools for creating bootable media and its main advantage is ease of use. In order to create a bootable flash drive with its help, it is enough to have the initial image of the bootable system and be able to click on the “Start” button. All selectable parameters and settings, by default, are already designed for using the program to work on a computer with a standard configuration.
The most simple and convenient to use Rufus to create a bootable flash drive (bootable USB drive) from ISO images of Windows or Linux installation disks, as well as emergency system recovery disks and diagnostic tools.
When creating a bootable Windows flash drive, it is enough to select the device on which the recording will be performed and the bootable iso-image file. The program will substitute other parameters itself.
If there is no ISO image file available, then it can be created from a physical CD (or from a set of distribution files) using CD / DVD burning programs such as the well-known Nero, Alcohol, or freely distributed CDBurnerXP or ImgBurn.
The procedure for creating a bootable Windows flash drive is as follows:
select the flash drive to which the image will be written. Unlike many similar programs, Rufus displays the volume label, drive letter and size, so if there are several removable drives in the system, it's easy to choose the one to write to.
select partition scheme and system interface type. Rufus allows you to create flash drives for booting in a regular BIOS interface and for booting in a UEFI environment, create boot records for MBR volumes and GPT volumes. The default mode is "MBR for computers with BIOS or UEFI" - the most common mode for bootable flash drives today.
select the file system that will be used on the created bootable flash drive. By default, bootable Windows flash drives use the file system FAT32, but if necessary, you can choose NTFS if you want to use files larger than 4 GB.
set the cluster size. The cluster size is selected by the program based on the image data and file system type, but if necessary, it can be changed.
specify the volume label that will be set for the created flash drive.
set formatting options. It is best to leave these options at their default and simply select the ISO image file. For images created by the program dd on Linux, you need to select the option DD image.
After pressing the button Start the program will format the flash drive, set the active partition flag, write the master boot record and partition boot record, as well as bootable media data from the ISO image. After completion of work Rufus you can boot using the resulting bootable flash drive.
Using virtualization technology to test bootable flash drives. Download links for free and handy programs to simplify the process of creating, debugging and checking the created bootable media.
