I have somehow managed to write an iso 9660 image onto my USB drive, which makes all my computer think that the device is actually a CD. I have tried various methods of removing this partition, but nothing seems to work. I have tried fdisk, which says

$ fdisk -l /dev/sdb
Cannot open /dev/sdb
parted crashes when I try to use it on this device.

I have even tried

$ dd if=/dev/zero of=/dev/sdb
but it just hangs with no output (either on screen or on disk). However, when I plug the USB in, it does mount, and I can view (but not edit) the files on it.

edit: now the result is

$ dd if=/dev/zero of=/dev/sdb
dd: opening `/dev/sdb': Read-only file system

I have also tried re-formatting it on Windows, but it gets to the end of the format process and then says "Couldn't format the drive".

How can I remove this partition and get my whole USB drive back to normal again?

EDIT 1: Trying a simple mkfs doesn't work:

$ sudo mkfs -t vfat /dev/sdb
mkfs.vfat 3.0.0 (28 Sep 2008)
mkfs.vfat: Will not try to make filesystem on full-disk device '/dev/sdb' (use -I if wanted)
I can't do mkfs on /dev/sdb1 because there is no such partition, as shown:
$ ls /dev | grep sdb

EDIT 2: This is the information posted by dmesg when I plug the device in:

$ dmesg
. (snip)
usb 2-1: New USB device found, idVendor=058f, idProduct=6387
usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 2-1: Product: Mass  Storage
usb 2-1: Manufacturer: Generic
usb 2-1: SerialNumber: G0905000000000010885
usb-storage: device found at 4
usb-storage: waiting for device to settle before scanning
usb-storage: device scan complete
scsi 6:0:0:0: Direct-Access     FLASH    Drive  AU_USB20  8.07 PQ: 0 ANSI: 2
sd 6:0:0:0: [sdb] 4069376 512-byte hardware sectors (2084 MB)
sd 6:0:0:0: [sdb] Write Protect is off
sd 6:0:0:0: [sdb] Mode Sense: 03 00 00 00
sd 6:0:0:0: [sdb] Assuming drive cache: write through
sd 6:0:0:0: [sdb] 4069376 512-byte hardware sectors (2084 MB)
sd 6:0:0:0: [sdb] Write Protect is off
sd 6:0:0:0: [sdb] Mode Sense: 03 00 00 00
sd 6:0:0:0: [sdb] Assuming drive cache: write through
 sdb: unknown partition table
sd 6:0:0:0: [sdb] Attached SCSI removable disk
sd 6:0:0:0: Attached scsi generic sg2 type 0
ISO 9660 Extensions: Microsoft Joliet Level 3
ISO 9660 Extensions: RRIP_1991A
SELinux: initialized (dev sdb, type iso9660), uses genfs_contexts
CE: hpet increasing min_delta_ns to 15000 nsec
This shows that the device is formatted as ISO 9660 and that it is /dev/sdb.

EDIT 3: This is the message that I find at the bottom of dmesg after running cfdisk and writing a new partition table to the disk:

SELinux: initialized (dev sdb, type iso9660), uses genfs_contexts
sd 17:0:0:0: [sdb] Device not ready: Sense Key : Not Ready [current] 
sd 17:0:0:0: [sdb] Device not ready: <> ASC=0xff ASCQ=0xffASC=0xff <> ASCQ=0xff
end_request: I/O error, dev sdb, sector 0
Buffer I/O error on device sdb, logical block 0
lost page write due to I/O error on sdb

  • Are you sure it is always loading at /dev/sdb? If you look at the end of /var/log/messages after the device is installed you will see the log messages relating to its automount. – mas Jul 29 '09 at 6:20
  • 3
    Are you sure it isn't currently mounted with cdfs or the equivalent? – RBerteig Jul 29 '09 at 6:46
  • 1
    @Slink84: I think I just went sudo dd if=some.iso of=/dev/sdb - I can't remember doing anything else that could do it – a_m0d Jul 29 '09 at 6:57
  • 1
    The image was an eeebuntu-3.0.0-standard image - don't know who makes the device, but I think that it is Toshiba – a_m0d Jul 29 '09 at 23:02
  • 1
    From the VID/PID pair, it is made by "Alcor Micro Corp.", and is a "Transcend JetFlash Flash Drive". I use the list at linux-usb.org/usb.ids to look these things up. – RBerteig Jul 30 '09 at 7:22

14 Answers 14


Okay, it turns out that in this case something (possibly when I wrote the iso-9660 file system to the drive) has triggered some form of internal write protection on the drive. There are no external write protection / hold switches, but yet this is the output in dmesg when I run

dd if=/dev/zero of=/dev/sdb

as root:

sd 9:0:0:0: [sdb] Add. Sense: Write protected
end_request: I/O error, dev sdb, sector 4028744
sd 9:0:0:0: [sdb] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE,SUGGEST_OK
sd 9:0:0:0: [sdb] Sense Key : Data Protect [current] 
Info fld=0x0

Note the comments in there about protection! However, when I plug the device in, I get,

scsi 10:0:0:0: Direct-Access     FLASH    Drive  AU_USB20  8.07 PQ: 0 ANSI: 2
sd 10:0:0:0: [sdb] 4069376 512-byte hardware sectors (2084 MB)
sd 10:0:0:0: [sdb] Write Protect is off
sd 10:0:0:0: [sdb] Mode Sense: 03 00 00 00
sd 10:0:0:0: [sdb] Assuming drive cache: write through
sd 10:0:0:0: [sdb] 4069376 512-byte hardware sectors (2084 MB)
sd 10:0:0:0: [sdb] Write Protect is off
sd 10:0:0:0: [sdb] Mode Sense: 03 00 00 00
sd 10:0:0:0: [sdb] Assuming drive cache: write through

Note that this message says that the device is not write protected! So unfortunately, it looks like the disk has had it (i.e kaput).

  • I heard in the past about flash devices which became bricked if you ever used a non-FAT filesystem with them (because they used the FAT to know which blocks were unused and could be discarded). I have not heard of that for a long time, and I could not find anything about it with a quick Google search. – CesarB Aug 25 '09 at 15:24
  • So far I have found one person mentioning the FAT dependency: linux.derkeiler.com/Mailing-Lists/Debian/2008-08/msg00761.html – CesarB Aug 25 '09 at 15:38
  • Sorry to hear that it's dead... Heh, I should be glad that I didn't manage to reproduce your problem :] Although I've tried it on an old 'disposable' drive, it still would be sad to lose it that way. – Kirill Strizhak Sep 2 '09 at 6:27
  • yeah, especially since it was only about a week old! oh well... – a_m0d Sep 3 '09 at 1:01
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    Found what I was looking for: lkml.org/lkml/2009/3/16/363 ("Some SDD manufacturers (I don't know which ones) are actually examining the partition table and doing different things. I know this because they are permanently bricked if one writes an invalid partition table.") – CesarB Sep 10 '09 at 18:04

I am new to this Linux sys admin stuff, so when I had exactly the same problem I poked and prodded with no madness to my method but managed to remove the iso9660 fs and reclaim the thumb drive.

sudo fdisk -l  /dev/sdb1


Disk /dev/sdb1: 16.0 GB, 16037969920 bytes
64 heads, 32 sectors/track, 15295 cylinders, total 31324160 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I>/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x57155aa7

     Device Boot      Start         End      Blocks   Id  System
/dev/sdb1p1            2048    31324159    15661056    5  Extended

So I then tried

sudo fdisk /dev/sdb1

Command (m for help): m
Command action
  . . .

followed by

Command (m for help): d Extended
Selected partition 1

Command (m for help): v
Remaining 31324159 unallocated 512-byte sectors

Then when prompted again selected for fdisk to create an empty dos partition table (something I figured I could overwrite with whatever I wanted later)

Command (m for help): v
Remaining 31324159 unallocated 512-byte sectors

Command (m for help): o
Building a new DOS disklabel with disk identifier 0xea06616f.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 22: Invalid argument.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

I took the returned messages to mean that I at least "broke" the iso9660 fs so went on to try mkfs

sudo mkfs /dev/sdb1

mke2fs 1.41.14 (22-Dec-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
979200 inodes, 3915520 blocks
.195776 blocks (5.00%) reserved for the super user
First data block=0
.Maximum filesystem blocks=4009754624
120 block groups
32768 blocks per group, 32768 fragments per group
8160 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208

Writing inode tables: done                            
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 28 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

All this left me with the "lost+found" directory on the thumb drive.

sudo mount /dev/sdb1 /media/
ls /media/

Finally, I went to the Ubuntu website (http://www.ubuntu.com/download/ubuntu/download, section 2) and used the stick to create a bootable image of Ubuntu for trial use, and it let me. The beauty of the Ubuntu images made on the stick this way is that they can be deleted easily and the stick reclaimed for other use.

I mention this very last step because in hindsight I wonder if I had done just that in the first place that it would have worked, I dunno. As mentioned, I am new to this Linux stuff and am trying different distro's (e.g. Fedora, Ubuntu, etc.) on live cd's with whatever media is most convenient, and I sure do break a lot of stuff along the way.

  • I'd love to try your steps to see if that would fix it, but I don't seem to have the stick anymore, so unfortunately I don't know if they would help. Nevertheless, this might still be helpful to others with the same problem. – a_m0d Nov 24 '11 at 4:22
mkdosfs -I /dev/sdb

will create a vfat file system on the drive. The -I has to be passed if you want the file system to be created on the entire drive and not on a partition. If you want to partition the drive first, use fdisk. Of course fdisk can't read the drive now, because it doesn't have any partitions. But I'm sure it will be able to write to it.

  • Doesn't work - just prints the version number and exits. Also, fdisk is "Unable to write /dev/sdb" – a_m0d Jul 29 '09 at 7:12
  • i just tried the command and it does write to the device specified. It also only prints the version number. You can test this with a regular file that you created with dd. You can see the changes it makes with od. My guess is that it's a hardware problem. – Kim Jul 29 '09 at 15:17
  • 1
    this worked for me to remove a Centos bootable image when the above solutions had all failed. – Ⴖuі Sep 7 '15 at 23:23

Looking at the dmesg snippet, it seems something is automaticaly mounting the drive (check with mount). Before doing anything with it, you should umount it by hand.

Then zero the block with the partition table (dd if=/dev/zero of=... bs=512 count=1), and run a partitioning tool to recreate an empty partition table. After that, unplug and replug (should not be needed, but...) and create/format the partitions you want on it. After creating the partitions (perhaps you will have to unplug and replug again), you should have /dev/sdb1 or something like that, which is where you should create the filesystem.

Note that all steps should be done as root (with sudo or an equivalent). Be careful to not write the wrong device name, or you could wipe your harddisk!

  • 1
    I have done that, but even though the whole disk seems to be filled with zeros, it still somehow mounts and reads the disk! – a_m0d Jul 29 '09 at 21:57

Last night I did

dd if=fedora.iso of=sdx  

After four hours I had an unbootable, unchangeable, iso9660 brick. Following David's train of thought, I called Ubuntu's 'startup disk creator' (Type 'startup disk creator' in the dash), and merely selected 'erase'. That did it.

The USB drive was then reported as FAT32 and all is well.

  • Sometimes it is appropriate to use a hammer, like this. I wonder what was in the first few sectors of the drive. – vgoff Nov 5 '12 at 15:20

I still feel that we are assuming something that's going to turn out to be untrue. Since the device is readable, this line will at least let you see the data for yourself, rather than depending on the other programs' interpretations.

 dd if=/dev/sdb  count=1 | xxd -g1 -u 

Also, maybe we could separate problems with the dev node from problems with what's on the device, by forcing it onto another port. Either plug it into another USB jack, or plug another drive in first, to occupy sdb.

  • hmm ... using this command tells me that the device is filled with zeros, which is probably because I finally managed to get dd if=/dev/zero of=/dev/sdb to run on it. But yet fedora still mounts the device as an ISO9660 fs when it is plugged in! – a_m0d Jul 29 '09 at 21:54
  • Does Linux still use /etc/fstab ? That's where these "associations" used to be stored. – gbarry Jul 30 '09 at 6:51
  • No, its using (I think) udev, or whatever it is that automatically mounts the drive. – a_m0d Jul 30 '09 at 13:39

Currently your USB drive got no partition table, iso9660 filesystem sits directly on whole disk (just like a cdrom)

sd 6:0:0:0: [sdb] Assuming drive cache: write through
 sdb: unknown partition table

I think you need make a partition first

sudo cfdisk /dev/sdb

(make sure it's not mounted before) in the fdisk application create a new partition.

after that is done, make the filesystem on the new partition

sudo mkfs -t vfat /dev/sdb1
  • Tried this; cfdisk doesn't produce any error messages, but a quick look in dmesg shows there is actually an error message. (see Edit 3 in question above) – a_m0d Jul 29 '09 at 22:00

I had the exact same problem as you. However, I was able to find a solution from a surprising place. An old laptop with Windows 98SE on it, which is the last Windows system I ever owned. Anyway just put it in and when you try to access the drive Windows will ask you if you'd like to format it. Click yes and you'll have a fat16 formatted drive that's fully functional. I don't know if it works with newer versions of Windows though. Best of luck.


Maybe with a simple

mkfs -t vfat /dev/sdb1
  • Doesn't work - see edit to question – a_m0d Jul 29 '09 at 6:18

The best and proper way to do it is:

# wipefs --all /dev/sdX

As from the wipefs manual:

wipefs can erase filesystem, raid or partition-table signatures (magic strings) from the specified device to make the signatures invisible for libblkid.

wipefs does not erase the filesystem itself nor any other data from the device. When used without any options, wipefs lists all visible filesystems and the offsets of their basic signatures.

wipefs calls the BLKRRPART ioctl when it has erased a partition-table signature to inform the kernel about the change.

This has many advantages like informing the kernel about the change (so you don't get any errors when formatting afterwards), not erasing data nor filesystems, and so on.


Remove the drive and see if you can still read from it. I wonder if somehow /dev/usb (or wherever you read from) has become an ordinary file directory.

  • Tried this - when I plug it back in, it mounts it fine, and I can read everything fine. According to mount, it is an iso9660 file system. However, gparted just shows 2GB of un-allocated space on the drive. dd complains that /dev/sdb is a read-only file system – a_m0d Jul 29 '09 at 7:49

Have you tried to re-mount it with -t option?

umount /dev/sdb
sudo mount -t vfat /dev/sdb /mnt/point

If that won't work, I'll try to reproduce it later, when I get home. Seems like an interesting problem. Will be fun to tinker with :]

  • Hah, nah, doesn't work, because mount checks the file type first – a_m0d Jul 29 '09 at 9:30
  • Yep, suspected as much :] Ok, no more 'out of the blue' ideas. – Kirill Strizhak Jul 29 '09 at 10:10

U3 has a utility to remove their U3 partition. It also removes the partition/device created by the utility that creates the iso 9660. This has been confirmed only on a u3 usb stick, but it is able to be formatted now and totally recover the entire space as a flash drive. You might give it a shot.


windows OS 2 things worked after many attempts

  1. using a program called victoria ,used to solve bad sector, Iused it to write to the flash usb but take care not to write to ur essential hard disk

  2. using easeuse partition master full version to wipe data on it 7 times then make primary partiton using it

  • This is a very old question that already has accepted answers. Your post lists a few general suggestions but does not explain how to use the tools it suggests to solve the problem that was presented. – music2myear Jan 21 at 3:34

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