boot drops to grub prompt, disk error

[Karl Auer]

I have a colleague whose Ubuntu 16.04 PC is dropping to a "grub>"
prompt. If he enters "exit", the grub prompt just returns. If he enters
"exit" a second time, the boot process proceeds normally. He says he
sometimes has to "exit" a third time.

Well, mostly normally - except at no stage does he see the usual grub
boot selection menu. This was a problem because in a separate issue he
had screwed up his password and could not get to the recovery option. I
fixed the password issue by booting off a USB stick, chrooting to the
old disk and running passwd.

Using "ls" at the grub prompt shows two disks, but the second one seems
to have errors:

(hd1) error: failure reading sector 0xfc from 'hd1'
error: failure reading sector 0xe0 from 'hd1'
error: failure reading sector 0x0 from 'hd1'

It goes past too fast to see, but after entering "exit" and before the
grub prompt reappears, or after entering "exit" and before the boot
process clears the screen, we are seeing what could be similar messages
flash up - a group of maybe six or seven of them.

Although he could continue to boot (off the first disk), the second
disk was not visible after booting - "fdisk -l" showed only the first
disk.

The disk involved is a 3TB WD Black. It's less than a year old, and has
barely been used. It hasn't been abused either.

A possibly related symptom - grub takes quite a long time to appear,
longer than it used to. This is quite a fast system, so the delay is
unexpected. When booted, the entire system seems to be running slowly,
also unexpected. Not sure how that would be hanging together with the
sector read error...

Thoughts? My feeling is that this is a defective hard disk and should
be replaced under guarantee.

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer
http://twitter.com/kauer389

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