Which extension can be used for the repair of a USB-MBR ?

[floppy]

.. instead of starting a UBCD or others.
(The USB is a Memory stick)

[gerald_clark]

You don't 'repair' an MBR.
Just install the boot loader of your choice.
Read the instructions for the boot loader, or use google.

[floppy]

Sorry, I dont understand.
A colleagues gave me a USB memory.
With connection to the PC, it show a "sde" in dmesg.
But it cannot boot with the mntools of TinyCore.
So, something is wrong. The partition array? How to repair it?
No bootloader is on that USB.

[tinypoodle]

Have a look at it with testdisk.
If you don't care about existing data, you could use gparted to partition.

[gerald_clark]

mnttools does not 'boot' anything.
It sounds like your USB device is not partitioned.
mnttool expects all external drives to be partitioned.
You can try manually mounting it.
mkdir /mnt/sde
mount /dev/sde /mnt/sde
If that does not work, the device is not mountable with any installed filesystem.

[floppy]

it was readable and partitionned.
After connecting and disconnecting from a Windows PC, it cannot be read anymore.
I will use testdisk.

[gerald_clark]

USB flash drives die suddenly without warning.
If it is no longer accessible by Linux or Windows, it may have died.

[genec]

USB flash drives die suddenly without warning.
If it is no longer accessible by Linux or Windows, it may have died.

Also, if you're not in the habit of doing "Safely Eject Hardware" or the equivalent AND waiting for the LED to stop blinking (I normally count 3-5 after the last blink for good measure), it may have "lost" the first block.  NAND block size is often ~1MiB.

[tinypoodle]

Can "sync" and "umount" before unplugging help to prevent such?

[gerald_clark]

umount calls sync. Just make sure to umount.  Umount will return when all data is written.

[genec]

umount calls sync. Just make sure to umount.  Umount will return when all data is written.

HOWEVER, you still need to wait for the flash drive to show as ready after umount completes.  One of the lies of flash media.  The media system will report to the OS that it's done when it's not.

[aus9]

on the dangers of usb, here is a suggestion

pretend you copy a large file to stick, on my system, there is a pause, then I look for the flashing light on the usb stick,
when flashing stops I know file is written, then it should be safe to umount.

[genec]

on the dangers of usb, here is a suggestion

pretend you copy a large file to stick, on my system, there is a pause, then I look for the flashing light on the usb stick,
when flashing stops I know file is written, then it should be safe to umount.

No need.  It's quite safe if you umount then watch for it to stop.  umount may still write to metadata after dumping your data, including marking the file system as cleanly unmounted.

[tinypoodle]

umount calls sync. Just make sure to umount.  Umount will return when all data is written.

HOWEVER, you still need to wait for the flash drive to show as ready after umount completes.  One of the lies of flash media.  The media system will report to the OS that it's done when it's not.

Good to know that, thank you