"No space left on device" when using dd to create a disk image - linux

Question

I am trying to trying to create a disk image of my Raspberry Pi Model 3 B+ onto a USB drive using dd. I know there are easier ways to do this on a Raspberry Pi, but I want to try this to test the procedure on a 'sacrificial' system, which I hope to then use on another linux computer running a much larger Ubuntu disk to create a backup. OS is Raspbian Buster 10.
I have been following a procedure I found on an article here: https://www.makeuseof.com/tag/easily-clone-restore-linux-disk-image-dd/
The USB drive has 64GB capacity and has been formatted, initially as exFAT but I also tried NTFS thinking maybe that was the issue. The command ended with the same error, however each time i have tried this the file size transferred has been different, varying from 2-8GB in size before the error occurred.
This is to identify my drives - the SD card is "mmcblk" and my USB drive is "sda", called "NINJA":
pi#raspberrypi:~ $ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 1 57.9G 0 disk
└─sda1 8:1 1 57.9G 0 part
mmcblk0 179:0 0 14.9G 0 disk
├─mmcblk0p1 179:1 0 256M 0 part /boot
└─mmcblk0p2 179:2 0 14.6G 0 part /
This my command I tried to use:
pi#raspberrypi:~ $ sudo dd bs=4M if=/dev/mmcblk0 of=/media/pi/NINJA/raspibackup.img
and this is the output:
dd: error writing '/media/pi/NINJA/raspibackup.img': No space left on device
605+0 records in
604+0 records out
2535124992 bytes (2.5 GB, 2.4 GiB) copied, 325.617 s, 7.8 MB/s

Answer 1

Check how much disk space is "Avail" on the target device.
Example:
[jack#server1 ~]$ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 484M 0 484M 0% /dev
tmpfs 496M 41M 456M 9% /dev/shm
tmpfs 496M 6.9M 489M 2% /run
tmpfs 496M 0 496M 0% /sys/fs/cgroup
/dev/mapper/centos-root 6.2G 6.2G 172K 100% /
/dev/sda1 1014M 166M 849M 17% /boot
tmpfs 100M 24K 100M 1% /run/user/1000
/dev/sr0 552M 552M 0 100% /run/media/jack/CentOS 7 x86_64
Terminology:
df: DiskFree
-h: Human Readable Sizes (Ex: 6.2G instead of 6485900)
In this example, let's say I want to make a backup of the Boot drive (/dev/sda1) and save it in my Local User Home Folder on my Root Drive (/dev/mapper/centos-root).
When I so this, I will get an error that looks like:
[jack#server1 ~]$ sudo dd if=/dev/sda1 of=boot.img
dd: error writing 'boot.img': No space left on device
1736905+0 records in
1736904+0 records out
889294848 bytes (889 MB) copied, 4.76575 s, 187 MB/s
Terminology:
sudo: Super User Do
dd: Disk Duplicate
if: Input File (source)
of: Output File (destination)
The system is trying to copy ALL of /dev/sda1 (to include freespace) to boot.img, which is impossible at this because /dev/sda1 is 1014M and there is only 172K space left on /dev/mapper/centos-root.
With that said, the actual size of the /dev/sda is actually 16G total! Which means that there is 8G not allocated.
My /dev/sda1 should be 1G where my /dev/sda2 (centos-root) should be 15G... in which it is currently 6.2G
[jack#server1 ~]$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 16G 0 disk
├─sda1 8:1 0 1G 0 part /boot
└─sda2 8:2 0 15G 0 part
├─centos-root 253:0 0 6.2G 0 lvm /
└─centos-swap 253:1 0 820M 0 lvm [SWAP]
sr0 11:0 1 552M 0 rom /run/media/jack/CentOS 7 x86_64
This partition can be extended by doing the following:
[jack#server1 ~]$ sudo lvextend -L +8G /dev/mapper/centos-root
[jack#server1 ~]$ sudo xfs_growfs /dev/mapper/centos-root
Now that my partition is extended, I can do another DiskFree command to double check.
[jack#server1 ~]$ df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 484M 0 484M 0% /dev
tmpfs 496M 33M 463M 7% /dev/shm
tmpfs 496M 6.9M 489M 2% /run
tmpfs 496M 0 496M 0% /sys/fs/cgroup
/dev/mapper/centos-root 15G 7.0G 7.3G 49% /
/dev/sda1 1014M 166M 849M 17% /boot
tmpfs 100M 24K 100M 1% /run/user/1000
/dev/sr0 552M 552M 0 100% /run/media/jack/CentOS 7 x86_64
My root partition is now 15G! Now I can perform my backup of the /dev/sda1 partition!
[jack#server1 ~]$ sudo dd if=/dev/sda1 of=boot.img
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 5.59741 s, 192 MB/s
Mission Complete!

Answer 2

sda1 is not mounted in /media/pi/NINJA/, the image you create is therefore stored on the mmcblk0p2 partition.
Since mmcblk0 is by definition larger than mmcblk0p2, you logically run out of space on it.
Solution :
You need to first mount sda1 using sudo mount /dev/sda1 /media/pi/NINJA/ and try your dd command again after.