Re: DD bs=4M option on USB mem-stick creates false format
On 03/26/2017 10:18 AM, kAt wrote:
dd if=/media/------/image.iso of=/dev/sdb bs=4M; sync
the image works but the format of the drive seems false gparted when
starting says that linux thinks it is a 256k block and not the 4m it
indicates. It shows on an 8G drive an empty space of 28G
Is it the option of bs=4M that creates this problem. The free space
can not be formatted and partitioned. As Gparted tried to claim and
format this space as a 6.7G which seemed right it crashed.
Any advise would greatly be appreciated
On 03/26/2017 10:41 AM, kAt wrote:
Correction to the error message, it is this: The driver descriptor
says the physical block size is 2048 bytes, but Linux says it is 512
bytes.
or at least that is what I get without using the bs=4M option
I am wondering whether it is a fault of the iso image (recent
download of the Rescatux 4.0beta) which I am trying to use without
luck on an old 32bit Celeron?? .. with Win XP to repair its admin
pass and booting which seems to take for ever.
I am trying to use the empty part of the stick to copy and store
temporatily some important files before I mess with it or install
debian
Please post console sessions -- prompt, command, and full output.
Paraphrasing and omitting information wastes everybody's time.
Always start a new thread with these:
2017-03-26 19:50:42 dpchrist@jesse ~
$ cat /etc/debian_version
8.7
2017-03-26 19:50:46 dpchrist@jesse ~
$ uname -a
Linux jesse 3.16.0-4-amd64 #1 SMP Debian 3.16.39-1+deb8u2 (2017-03-07)
x86_64 GNU/Linux
Also, please post the URL for image.iso/Rescatux 4.0beta.
Did you checksum your download? If not, checksum it. If the download
checksum is bad, download and checksum again until you get a good
checksum. For example:
2017-03-18 12:40:50 root@cd2533
/var/local/data/dpchrist/iso/debian/8.7.1/i386
# grep debian-8.7.1-i386-xfce-CD-1.iso SHA256SUMS
a258af89540a64e6d16d6a546ec554a07ef0d46168d74bfc2073cc60d6a9ecde
debian-8.7.1-i386-xfce-CD-1.iso
2017-03-18 12:41:30 root@cd2533
/var/local/data/dpchrist/iso/debian/8.7.1/i386
# sha256sum debian-8.7.1-i386-xfce-CD-1.iso
a258af89540a64e6d16d6a546ec554a07ef0d46168d74bfc2073cc60d6a9ecde
debian-8.7.1-i386-xfce-CD-1.iso
Did you checksum the image on your USB flash drive immediately after
burning? Use a calculator to find the largest power of 2 that divides
evenly into the image size:
2017-03-18 12:41:06 root@cd2533
/var/local/data/dpchrist/iso/debian/8.7.1/i386
# ll debian-8.7.1-i386-xfce-CD-1.iso
-rw-r--r-- 1 dpchrist dpchrist 678428672 2017/03/04 17:02:57
debian-8.7.1-i386-xfce-CD-1.iso
In this case, it's 2^20. Do the burn with 'bs=1M'. Also, run 'sync'
after 'dd' to ensure that the command prompt is not returned until all
the bytes have been written:
2017-03-18 12:41:54 root@cd2533
/var/local/data/dpchrist/iso/debian/8.7.1/i386
# time dd if=debian-8.7.1-i386-xfce-CD-1.iso of=/dev/sdc bs=1M; sync
647+0 records in
647+0 records out
678428672 bytes (678 MB) copied, 161.132 s, 4.2 MB/s
real 2m41.135s>
user 0m0.012s
sys 0m1.640s
Note '647+0 records in' and '647+0 records out'. The '647' part must
match and both must have '+0', or something is wrong. Use 'dd' with
'bs=1M' and 'count=647' to do the checksum:
2017-03-18 12:51:52 root@cd2533
/var/local/data/dpchrist/iso/debian/8.7.1/i386
# time dd if=/dev/sdc bs=1M count=647 | sha256sum
647+0 records in
647+0 records out
a258af89540a64e6d16d6a546ec554a07ef0d46168d74bfc2073cc60d6a9ecde -
678428672 bytes (678 MB) copied, 33.1367 s, 20.5 MB/s
real 0m33.141s
user 0m5.992s
sys 0m1.948s
Understand that many memstick images change once they have been booted,
so you must checksum them immediately after burning. (Thankfully,
debian-8.7.1-i386-xfce-CD-1.iso doesn't, so I can verify my USB flash
drive at any time.)
Once you are confident your USB flash drive has a good image, try
booting it in your newest x86 computer. If that fails, try other x86
computers. If none of them boot, contact your vendor.
If the USB flash drive boots correctly in newer computers, it is
probably in "isohybrid" format -- meaning, it's supposed to boot when
burned to optical media (CD-R, DVD-R, BD-R) and it's supposed to boot
when burned to a USB drive. I have found that this "one size fits most"
approach doesn't boot on all computers, especially older computers. If
this is the case, possible solutions include:
1. Burn the ISO image to optical media and boot that.
2. Download a memstick.img file that is meant to be burned to a USB
drive, burn it to a USB drive, and boot that. (If your vendor doesn't
offer such, you might need to find a different tool.)
David
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