Re: grub rescue> (getting error: unknown filesystem) for all filesystems!

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

aman nangia wrote:
>  i tried running dd
> if=/var/tmp/above-filename of=/dev/sdbe1 bs=4M; sync (where my sdbe1 was the
> usb flash drive).

I think the USB device address is not correct.
Firstly the bootable isohybrid images must be copied onto
the base device, not a partition device. So no "1" at the end.

Further "/dev/sdbe" is not what i would expect for a USB stick.
/dev/sdb or /dev/sde would be plausible.

So try first whether /dev/sdb is really your USB stick
by looking whether this read command lets it blink:

  dd if=/dev/sdb of=/dev/null

If the desired USB stick reacted, then you can dare to overwrite
it.

  # umount any mounted /dev/sdb*

  dd if=/var/tmp/above-filename of=/dev/sdb bs=4M; sync

This will overwrite the partitioning of the USB stick.
If any other valuable data are on it, make a backup first

  # umount any mounted /dev/sdb*

  dd if=/dev/sdb | gzip >"$HOME"/usb_sdb_backup.gz

(To be restored by
   dd if="$HOME"/usb_sdb_backup.gz | gunzip >/dev/sdb
 which will bring back all partitions and their content.
)


Debian's FAQ answer:
   https://www.debian.org/CD/faq/#write-usb
ISOLINUX isohybrid wiki:
   http://www.syslinux.org/wiki/index.php/Isohybrid#Copying_onto_USB_stick_by_shell_commands 


In a neighboring thread there was the question whether bs=8m
would be the right block size.
Answer:
It matters only for performance. The difference between bs=1
and bs=1M is noticable, the difference between 4M an 8M is not.


Have a nice day :)

Thomas