Sd card block size dd. dd is only safe on a static (unmounted) filesystem.

Sd card block size dd img file will be (a lot) bigger. 64 GiB, 64021856256 bytes, 125042688 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 Mar 2, 2015 · If you know for a fact that your 8GB image only has 7GB of allocated data (or less), you can tell dd to copy that exact amount to the new SD card. Even if you find a count that's the right size, there's an excellent chance the resulting image will be corrupt as the filesystem is almost certainly changing while you're going the dd. dd bs=512 The Any tips for finding the optimal block size when using the dd command to clone a disk? I’m cloning disks (disk to disk, not from an . I have done this by inserting the SD card into a laptop running Debian Bullseye and then running the command dd if =/dev/sdb of =/home/name/RPi4/img bs=1M This produces an img file in the home folder of 31. 9Gb. < 4GB so that I can then dd this onto a new 4GB card? Or is there a better solution that I should be using? Oct 23, 2013 · From this the only important info is: 7822376960 bytes. Enhance your skills with practical examples. Sep 28, 2015 · My edit /dev/block/mmcblk1p2 /system ext4 rw,barrier=1 wait and back in my linux box, I dd -ed the pristine backup of the tablet's system partition to my external SD card's 2nd partition - which I created via gparted to be exactly 2GB. My question: How can I mount these partitions from the . Apr 10, 2014 · The SD-card includes two partitions (one vfat, one ext4) which are automatically mounted when I plug the card in. buffer size) used for copying and this will result in no unnecessary bytes read - if you know how to use it, that is. For best cloning speed performance, you want to match any RAID stripe sizes or be a higher multiple of it. And I'd like to fill it with zeros, 100%. I’ve read a bit about adjusting the block size option to optimize the copy speeds and am interested in tweaking it to try and get the time down. It is almost certainly 512 bytes. img file? Jan 28, 2018 · This is a bit of a follow on from another users question found here: SD card cloning using the dd command I have used the dd command to clone or make backup copies of SD cards with limited success. Next, as we will use 'dd' command for copying data, we have to calculate some parameters for it. The illegal numeric value error happens because the dd on macOS expects lowercase letters, so change bs=32M to bs=32m (lowercase m). bin then the resulting . Here's a command to copy 7168 blocks of 1 Megabyte each: dd if=/path/to/file. img? My command and the final out put are below for reference. Usually I use bs=1M, but could I go any higher than that? Jan 4, 2015 · A pair of scripts to find more optimal block sizes Because of the wild variance in optimal block sizing, I've written a couple of scripts to test a range of different input and output block size options for use prior to starting any large copies with dd. Oct 5, 2013 · I hope you're not trying to use dd to copy a running SD card. I suspect you'll just have to wait. e. Basic Syntax The basic syntax of the dd command is as follows: Nov 20, 2019 · I want to use dd to clone my running Linux OS which is installed on a PI4 MicroSD 64GB media, to an image. We are interested in this 64GB SD card. gzip ensures these long 0x00 series are well compressed. And you can write to a block device with tee. Tyipcally when cloning disks, you’ll want to tack a k on the end; bs=1024k to read/write Jun 22, 2009 · How can I find out the size of a block device, such as /dev/sda? Running ls -l gives no useful information. I have tried two tools, linux's dd and balenaEtcher. bin is 16GB in size. 3 The conclusion from this benchmark is that the choice of block size for dd matters (but not that much), and cat automatically finds the best way to make a fast copy: dd can only slow you down. SD Card Copier comes preinstalled on desktop versions of raspbian and located under the Accessories menu. Nov 28, 2024 · I regularly have to flash an SD card with a . A fast USB 3 pendrive or fast memory card will be 5 times faster (~25 MB/s) even when connected via USB 2. Unmount the disk Unmount the disk called /dev/disk2: $ diskutil unmountDisk /dev/disk2 Here is what we see: Unmount of all volumes on disk2 was successful 3. Over the years, sizes slowly crept up as our t… The dd block size is just the data size chunk that dd reads/writes at. You can use head or cat for reading from a block device, and write to a regular file using a redirect. With a small block size, dd wastes time making lost of tiny reads and writes. 6 hours typical for a 16 gb sd card to be dd'd to a . Create the disk image with dd Finally create the disk image of the entire disk /dev/disk2: $ sudo dd if=/dev/disk2 of=backup. Jan 3, 2019 · It may improve dd speed as compared to smaller block size, but has no effect on the data itself. If you can find a larger SD card (such as a 64 GB card) then it will work fine with the sudo dd command you suggested: sudo dd bs=1024 if=/dev/mmcblk0 of=/dev/mmcblk1 Note that bs=1024 is going to be very slow. That did it - the tablet booted from my external SD card. Approved version. If you want to find the block size stat -c "%o" filename is probably the easiest option. sudo fdisk -l Returns a list of all of the available partitions and drives. Jun 23, 2015 · You have to copy the full size of the partition. For SSDs, I typically use either 64KB (bs=65536) or 512KB (bs=524288) which does a decent job of maxing out the available bandwidth to the device. com For example, a Samsung Evo+ 64GB SD card reports an erase block of 16MB. Approved on: 15:41, 27 June 2025 Pages How to populate the SD card with dd command Last edited 4 months ago May 18, 2016 · I have a somewhat weird situation I'm trying to dd an OS image (something which I dd'ed off a card earlier) onto an SD card. While it was originally designed for block-level operations on Unix systems, its application has expanded over the years. But the backup takes way longer than necessary. Mar 8, 2022 · Determine the Device Location We need to determine the path for the SD card we intend to use, whether the operation is reading or writing. If you have a page size of 16MB and write for example 2 MB, the SD card writes 16 MB (page size) for the first 2 MB because it always has to erase a full page before rewriting it. Jun 25, 2022 · The first line is the expected dd command, with the device name and file name being set to your current needs. Use a bigger value, at least 32M or 64M. So you're using a bs= of 2 to the power of 25 so about 33 million, that's big enough (fyi, using a small bs like 1 or 512 will usually slow dd to a crawl). It does the job ok but it takes a such long time to complete. The block size determines the amount of data that is read and written at a time during the copy process. 0-STABLE. May 19, 2012 · Hello, I use dd to make a back up of my 16gb sd card. This is because when doing large data transfer, we expect the operating system to automatically adjust block size (according to source block size, target block size, memory availability, etc. 11 I agree with geekosaur's answer that the size should be a multiple of the block size, which is often 4K. Jul 28, 2015 · Does block size changes performance of SD card or only cuts size of moving file using dd to sdcard? See full list on baeldung. Oct 19, 2020 · Block size = 512 size is 988282880 bytes In our example the microSD device name is: \\?\Device\Harddisk6\DR27 Please pay attention if your card reader has multiple slots and choose the right volume. 9 cat 41. Both flash drives were 2 GB and took about 2 minutes each to run each one. . Sep 21, 2025 · Master the versatile dd command in Linux! Learn to backup, convert, and wipe data efficiently. gz >/dev/sdb for convenience. Start low (4k) and work your way up. Jul 3, 2017 · This is the block size used for dd under the hood in mkusb. Mar 3, 2021 · I probably have a corrupted SD card. Having some trouble with writing to my SD card, burning NOOBS (New Out Of Box Software) software to my SD card for Raspberry Pi. It reads from an input file or stream and writes to an output file or stream, all while allowing various transformations in between. Generally, larger block sizes result in faster copy speeds, as they reduce the overhead associated with the read and write operations. May 29, 2020 · I am trying to clone the 32Gb micro SD card in my Raspberry Pi 4. The card capacity is 8GB and the image was made off an SD card of simi Aug 20, 2023 · What is dd? The dd command stands for Data Duplicator. Jan 9, 2025 · Use SD card with appropriate size, 16GB or larger is recommended Replace sdX with the actual block device name on your Linux host Flash the ZST image file to the micro-SD card: cd package_dir/images/ zstd -dc imx-image-full-ucm-imx95. And i had to use a 64Gb SD-card as my mmcblk0. Different story would happen if you read in chunks smaller than the sector size of the drive: drives have to serve full sector size and the kernel caches that information. Bigger values will usually yeld better performance, but will use more memory. I find that block size of 2^15 or 2^16 work best for my WDC (8mb cache) SATA drives connected to a Adaptec SAS RAID controller, 4x PCIe, 64-bit FreeBSD 8. Choosing the optimal block size can significantly improve the overall performance of the dd command. The second line sets the block size for dd to the sector size of the SD card. img file) and right now it takes 63 minutes to copy 128gb. Aug 8, 2015 · Explains how to use the dd command for simple sequential disk I/O performance measurement on a Linux or Unix-like systems. ) for optimal performance, and it turns out they work faster than dd if Apr 23, 2024 · Try to use a reasonable block size. img seems to be bigger as yours (and the SD-card hosts some files in the android-folder, onces the phone was booted). There's absolutely no May 15, 2021 · NOTE: Unlike the PiShrink option with this scenario you can save time and space by not having to create a full image with dd, especially when sdcard capacity is high, ie a 128/256GB sdcard with only a few GB of actual data. Now I need a calculator can't find one, just bc. You can't limit it to just the used space with dd as dd doesn't know where in the partition the used space is. Mar 9, 2015 · $ dd if=/dev/dvd of=foobar. img of=/dev/sdX bs=1M count=7168 You should actually specify the exact size when creating your backups, which would also make them somewhat smaller. If you are 100% certain it is 512, you can replace the line with bs=512. Some SD cards / adapters are very picky about what sizes they will accept writes. img of=/dev/mmcblk0 bs=1M status=progress The write operation is much slower than before. rootfs*zst | sudo dd bs=1M status=progress of=/dev/sdX Run Yocto Linux image Insert the micro-SD card into its Oct 7, 2024 · H ow do I create disk image using dd command? How do I perform disk cloning from a live Linux cd for backup or recovery purpose? You can easily use the dd command for making an image of a partition or an entire hard disk drive. img. Some devices / controllers may insist on even lower block sizes. Disk /dev/mmcblk0: 59. Under what circumstances would it be problematic to not specify bs= or count= when copying from a device of finite size? Feb 4, 2015 · When using dd you can control the block size (aka. And if the source disk is in bad condition, then dd isn't a really good option too, use ddrescue Mar 31, 2016 · With dd command you can do the following awesome things. Owing to their compact form factor, SD cards have been widely adopted in a variety of portable consumer electronics, including digital cameras, camcorders, video game bs= sets the block size in bytes, which is the amount of data dd operates on at once. Oct 17, 2012 · So dd will read ALL the SD card, also a loaaaads of continuous 0x00 series. Let us see how to make disk image with dd command on your Linux or Unix machine. Mar 17, 2025 · But with so many different sizes and types of SD cards available, many people find themselves asking the deceptively simple question: What size SD card do I need? This comprehensive guide will break down everything you need to consider to make the right choice. ('bs' as in block size) bs=1M (kilo times kilo equals mega: 1024 * 1024 = 1M) ('count' as in number of blocks to copy) count=7460 (divide target size with block size to get number of blocks: 7822376960 / (1024 * 1024) = 7460) Do the copy As Aug 29, 2015 · I typically use unzip -p 2015-11-21-raspbian-jessie. Here is th Sep 8, 2020 · The SD card first burst onto the scene in 1999, with cards boasting storage capacities up to 64 MB hitting store shelves in the first quarter of 2000. I know there are easier ways to do this on a Raspberry Pi, but I want to try this to test the Sep 12, 2014 · dd bs=4k 48. Defaults to 512 bytes, which is the "classic" block size for hard drives since the early 1980s, but is quite slow. You should explicitly state the buffer size, so try dd if=/dev/sda of=/dev/sdb bs=16M IIRC, the default buffer size is only 512 bytes. See Matthew Ife's answer on the same Serverfault post. I want to clone the content into a 16GB card. Am i using the correct dd command in OS X to get the job done swiftly or is 6. bs=32k works, but bs=1M or bigger does not. If the device is different (USB or other type of SD card reader) verify its name and be sure to unmount it: sudo fdisk -l sudo umount /dev/mmcblk0 Write the image to the device: sudo dd if=~/sd-card-copy. Jul 24, 2012 · If you get only one partition when cloning the image to an sd card, make the block size smaller when executing the dd command. Then clone SD card with Donemax Disk Clone on Windows. Oct 18, 2015 · In this example my SD card size is 4GB and located at /dev/disk2. Aug 13, 2021 · It looks like your SD card is every so slightly smaller than the built-in eMMC in the Jetson. Before you do anything fancy, insert your Micro SD Card into a USB adapter and plug it into your Linux PC. Is there a way to use dd to copy just what's actually being used, i. Using GParted, I shrank the partitions to be less than 16GB and here is the state of the SD Card as shown in fdisk. zip >/dev/sdb or zcat 2015-11-21-raspbian-jessie. Is there an optimal value for the blocksize parameter that will speed up the cloning procedure? Answer: 64k seems to be a good pick: May 29, 2021 · 5 I have a 32GB SD Card that contains an Armbian installation for some pi gadget. block size also has a lot to do with performance. wic image. On my first two USB's I ran the command dd if=/dev/sda of='filename'. See this link and links from it, As long as the block size (bs) used with dd is big enough, it's really only limited by hardware speed. But say you do dd bs=4K, that means it does read(4096); write(4096); read(4096); write(4096) Additional "storage" partition, FAT, 1GB If I use dd to create an image of the card via: dd if=/dev/sdb of=~/sd-card. sdcard-18-oct-2015. As far as it looks on the surface, changing around the block size and count really just changes the fineness of the grain I can use to control the final size of the image file. They come in three physical forms: the full-size SD, the smaller miniSD (now obsolete), and the smallest, microSD. Things may have changed since I tested different block sizes, but I think the speed in your case is limited by the flash memory hardware. the dd default is antiquated and terrible for modern, high capacity applications I have used this script in the past and it optimized me at 16MB on a 1TB nvme and reduced the copy time from 23 hours to 23 minutes. Dec 11, 2012 · Once it's finished, insert the empty SD card. 2. So what commands should I type, assuming the device is /dev/sdc? Jun 4, 2010 · Fair warning that some devices only support one block size, though this is rare, and usually drivers make up the difference anyway. Jun 10, 2025 · Before we start: It's necessary to get the target SD card or drive ready first. On my third USB, which is 4 GB, I have had to cancel the dd three times because it is running right around 35 kB/s! I tried adding the block size parameter bs=1M to the command 49 dd has many (weird) options, see dd (1). 7 cp 45. Because it is a Raspberry PI I cannot (easily) boot from a USB stick and run the job with May 6, 2009 · Also note than most of the times, dd program is unnecessary. Usually, it's the last one from the list showing the actual size of the microSD card in bytes Use this command to write the image to the microSD card: May 20, 2018 · You need to diskutil unmountDisk /dev/disk2 before doing dd. I think that maximum physical I/O size is limited to 1MB on FreeBSD, but I could be outdated on that. The command above sets it to 16 megabytes. It is possible, even likely, that the sd card For my senior project I am tasked with performing forensics on USB drives. For SD, “erase_size” is 512 if the card is block-addressed, 0 otherwise. Attempted to use the following command as root: # dd bs=1M if=/home/ Jun 12, 2018 · Furtheron, i had to use a exFAT formatted SD-card, as FAT32 maxfile size is 4Gb and the mmcblk0. Then you won't have to guess a good block size, and it's likely going to be faster too. SD/MMC cards can erase an arbitrarily large area up to and including the whole card. If you are using Mac or Linux systems, you can use Disk Utility or dd command to clone the SD card. balenaEtcher finishes the job in about 2 minutes while my dd command takes 5. Mar 7, 2015 · I want to run dd over a SanDisk 32GB micro SD but I'm not sure how to decide on the block size. Mar 13, 2024 · Am I correct in assuming that the dd command backs up the whole device and so makes a file size that is equal to the whole SD card size? Yes, dd does a block-by-block copy Sep 12, 2019 · I am trying to trying to create a disk image of my Raspberry Pi Model 3 B+ onto a USB drive using dd. The SD card is a proprietary, non-volatile, flash memory card format developed by the SD Association (SDA). my. dd is only safe on a static (unmounted) filesystem. Mar 3, 2021 · What is the maximum size of SD card that, I can use with ST controller for storing data? Please suggest the controller series also. This makes 8x more writes than necessary. 5 dd bs=512 48. iso bs=2048 Why must the block size be specified? I noticed that in fact 2048 is the standard logical block size for CDROM images but it seems that dd without specifying bs= or count= works as well. This. 16 MB for the second 2 MB block and so forth. Jan 8, 2022 · Good block size for disk-cloning with diskdump (dd) Jan 8, 2022 Question: I use dd in its simplest form to clone a hard drive: dd if=INPUT of=OUTPUT However, I read in the manpage that dd knows a blocksize parameter. vun pkul xeqs epci nkxcgqx lvba thg zve knvnz jvz vlrdjvjh srjwoy byctq mynjjj dqjryh