I've been trying to restore a recent deja dup backup to an
external storage device (I've tried a 1TB HD and a USB stick) as
I need to access some files. I'm having to do this with an old
DVD with a 17.2 iso on it. The backup restore proceeds ok, and I
can watch deja dup write the files to the external storage
device. But I can't see them with the iso's file manager! The
folder has nothing in it, but "properties" shows the device free
memory decreasing and the number of files increasing . I tried
using the file manager with elevated privileges, but although it
seems to appear I was not asked for a sudo password, and no files
were visible. Is this a permission issue? If so, how do I get
access to view the files?

This is necessary as the laptop's HD has suddenly become
inaccessible by the Bios, and booting is not possible.

--
Jeff

----Android NewsGroup Reader----
https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html

On 2024-03-03, Jeff <jeff@invalid.invalid> wrote:
> I've been trying to restore a recent deja dup backup to an
> external storage device (I've tried a 1TB HD and a USB stick) as
> I need to access some files. I'm having to do this with an old
> DVD with a 17.2 iso on it. The backup restore proceeds ok, and I
> can watch deja dup write the files to the external storage
> device. But I can't see them with the iso's file manager! The
> folder has nothing in it, but "properties" shows the device free
> memory decreasing and the number of files increasing . I tried
> using the file manager with elevated privileges, but although it
> seems to appear I was not asked for a sudo password, and no files
> were visible. Is this a permission issue? If so, how do I get
> access to view the files?
>
> This is necessary as the laptop's HD has suddenly become
> inaccessible by the Bios, and booting is not possible.
>
iso files need to be mounted in order to see the files within.

Why are you creating and iso?

A restore should just list the files as a directory which given the correct
permissions are readable with a file manager, (or ls.)

Gordon <Gordon@leaf.net.nz> Wrote in message:r
> On 2024-03-03, Jeff <jeff@invalid.invalid> wrote:> I've been trying to restore a recent deja dup backup to an> external storage device (I've tried a 1TB HD and a USB stick) as> I need to access some files. I'm having to do this with an old > DVD with a 17.2 iso on it. The backup restore proceeds ok, and I> can watch deja dup write the files to the external storage> device. But I can't see them with the iso's file manager! The> folder has nothing in it, but "properties" shows the device free> memory decreasing and the number of files increasing . I tried> using the file manager with elevated privileges, but although it> seems to appear I was not asked for a sudo password, and no files> were visible. Is this a permission issue? If so, how do I get> access to view the files?>> This is necessary as the laptop's HD has suddenly become> inaccessible by the Bios, and booting is not possible.>iso files need to be mounted in order to see the files within.

Why are you creating and iso?A restore should just list the files
as a directory which given the correctpermissions are readable
with a file manager, (or ls.)

The Mint 21.3 on the laptop's HD is not accessible as the HD has
failed and I can't boot to it. I have now been able to boot to a
live 21.2 iso and can get to the deja dup backup of my Home
folder on a USB stick. I can "restore" the files on that to an
external HD but can't access them. I can't even see them on that
external HD using the live iso's file manager. It just reports
that the folder I restored to has 0 bytes! Yet I know the HD free
capacity has decreased by over 100 GB, so the files are on it.
How can I view them?

--
Jeff

----Android NewsGroup Reader----
https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html

On 3/4/2024 1:49 AM, Jeff wrote:
> Gordon <Gordon@leaf.net.nz> Wrote in message:r
>> On 2024-03-03, Jeff <jeff@invalid.invalid> wrote:> I've been trying to restore a recent deja dup backup to an> external storage device (I've tried a 1TB HD and a USB stick) as> I need to access some files. I'm having to do this with an old > DVD with a 17.2 iso on it. The backup restore proceeds ok, and I> can watch deja dup write the files to the external storage> device. But I can't see them with the iso's file manager! The> folder has nothing in it, but "properties" shows the device free> memory decreasing and the number of files increasing . I tried> using the file manager with elevated privileges, but although it> seems to appear I was not asked for a sudo password, and no files> were visible. Is this a permission issue? If so, how do I get> access to view the files?>> This is necessary as the laptop's HD has suddenly become> inaccessible by the Bios, and booting is not possible.>iso files need to be mounted in order to see the files within.
>
> Why are you creating and iso?A restore should just list the files
> as a directory which given the correctpermissions are readable
> with a file manager, (or ls.)
>
> The Mint 21.3 on the laptop's HD is not accessible as the HD has
> failed and I can't boot to it. I have now been able to boot to a
> live 21.2 iso and can get to the deja dup backup of my Home
> folder on a USB stick. I can "restore" the files on that to an
> external HD but can't access them. I can't even see them on that
> external HD using the live iso's file manager. It just reports
> that the folder I restored to has 0 bytes! Yet I know the HD free
> capacity has decreased by over 100 GB, so the files are on it.
> How can I view them?
>

sudo apt install disktype

sudo disktype /dev/sdb # Substitute the identifier for the external disk into this command
# in place of sdb.

This will attempt to identify file systems on the disk.

A utility like "testdisk" can also be installed and used
to examine the external disk drive.

*******

We could use a few breadcrumbs.

Does "deja-dup" have a log output ?

If it proposes to have done certain things to /dev/sdb,
this would be useful info.

Paul

On 3/4/2024 1:49 AM, Jeff wrote:
> Gordon <Gordon@leaf.net.nz> Wrote in message:r
>> On 2024-03-03, Jeff <jeff@invalid.invalid> wrote:> I've been trying to restore a recent deja dup backup to an> external storage device (I've tried a 1TB HD and a USB stick) as> I need to access some files. I'm having to do this with an old > DVD with a 17.2 iso on it. The backup restore proceeds ok, and I> can watch deja dup write the files to the external storage> device. But I can't see them with the iso's file manager! The> folder has nothing in it, but "properties" shows the device free> memory decreasing and the number of files increasing . I tried> using the file manager with elevated privileges, but although it> seems to appear I was not asked for a sudo password, and no files> were visible. Is this a permission issue? If so, how do I get> access to view the files?>> This is necessary as the laptop's HD has suddenly become> inaccessible by the Bios, and booting is not possible.>iso files need to be mounted in order to see the files within.
>
> Why are you creating and iso?A restore should just list the files
> as a directory which given the correctpermissions are readable
> with a file manager, (or ls.)
>
> The Mint 21.3 on the laptop's HD is not accessible as the HD has
> failed and I can't boot to it. I have now been able to boot to a
> live 21.2 iso and can get to the deja dup backup of my Home
> folder on a USB stick. I can "restore" the files on that to an
> external HD but can't access them. I can't even see them on that
> external HD using the live iso's file manager. It just reports
> that the folder I restored to has 0 bytes! Yet I know the HD free
> capacity has decreased by over 100 GB, so the files are on it.
> How can I view them?
>

I did a test restore here, using a random partition created in gparted.
And I didn't have permission to write to the top level, as
an ordinary user.

cd /media/mint/BACKUP # My new "external" drive in a virtualbox guest
# I could have made this just as easily with fdisk and friends

sudo mkdir restore # Made my first directory as root

sudo chown bullwinkle:bullwinkle restore # change the ownership for restoration run, 755 perms already present

deja-dup # Restore to /media/mint/BACKUP/restore

Result is in /media/mint/BACKUP/restore/home/bullwinkle
and includes lots of dot files, plus the usual things
like a Pictures folder.

The screenshot here, the details of how or what don't matter,
this is just a quick listing to show what my restoration got me.
It kinda looks like a home directory.

[Picture]

https://i.postimg.cc/SsXVX9WY/deja-dup-restore.gif

Since my backup was a Full and there are no Incrementals,
there is just the one tar.gz file containing my home directory.
It's possible the marked file would open in Archive Manager,
as an example.

duplicity-full.20240305T012151Z.manifest
duplicity-full-signatures.20240305T012151Z.sigtar.gz
duplicity-full.20240305T012151Z.vol1.difftar.gz <=== 8 megabytes compressed

If you did a Full backup on Sunday, an Incremental on Monday, an Incremental on Tuesday,
to restore to Tuesday onto an external drive, Deja-dup would

unzip the Full onto the output drive
unzip Monday onto the output drive (replacing files with newer ones)
unzip Tuesday onto the output drive (replacing files with newer ones)

Done in an unintelligent way, this takes slightly more time, but isn't
that bad all things considered. Some dedicated backup/restore programs
would likely have a more efficient algorithm for deciding which
files to grab from each of the tar.gz things.

But the software doesn't exactly tell you what it's doing,
and it is more opaque than I expected.

bullwinkle@LMDE6TST:~$ apt search dirstat
p k4dirstat - graphical disk usage display with cleanup
p k4dirstat:i386 - graphical disk usage display with cleanup
p qdirstat - Qt-based directory statistics
p qdirstat:i386 - Qt-based directory statistics

sudo apt install qdirstat # Because pulling in all of KDE isn't all that good

sudo qdirstat /media/mint/BACKUP # Enumerate my destination drive, look for space wasters

Paul

On 05/03/2024 02:36, Paul wrote:
> On 3/4/2024 1:49 AM, Jeff wrote:
>> Gordon <Gordon@leaf.net.nz> Wrote in message:r
>>> On 2024-03-03, Jeff <jeff@invalid.invalid> wrote:> I've been trying to restore a recent deja dup backup to an> external storage device (I've tried a 1TB HD and a USB stick) as> I need to access some files. I'm having to do this with an old > DVD with a 17.2 iso on it. The backup restore proceeds ok, and I> can watch deja dup write the files to the external storage> device. But I can't see them with the iso's file manager! The> folder has nothing in it, but "properties" shows the device free> memory decreasing and the number of files increasing . I tried> using the file manager with elevated privileges, but although it> seems to appear I was not asked for a sudo password, and no files> were visible. Is this a permission issue? If so, how do I get> access to view the files?>> This is necessary as the laptop's HD has suddenly become> inaccessible by the Bios, and booting is not possible.>iso files need to be mounted in order to see the files within.
>>
>> Why are you creating and iso?A restore should just list the files
>> as a directory which given the correctpermissions are readable
>> with a file manager, (or ls.)
>>
>> The Mint 21.3 on the laptop's HD is not accessible as the HD has
>> failed and I can't boot to it. I have now been able to boot to a
>> live 21.2 iso and can get to the deja dup backup of my Home
>> folder on a USB stick. I can "restore" the files on that to an
>> external HD but can't access them. I can't even see them on that
>> external HD using the live iso's file manager. It just reports
>> that the folder I restored to has 0 bytes! Yet I know the HD free
>> capacity has decreased by over 100 GB, so the files are on it.
>> How can I view them?
>>
>
> I did a test restore here, using a random partition created in gparted.
> And I didn't have permission to write to the top level, as
> an ordinary user.
>
> cd /media/mint/BACKUP # My new "external" drive in a virtualbox guest
> # I could have made this just as easily with fdisk and friends
>
> sudo mkdir restore # Made my first directory as root
>
> sudo chown bullwinkle:bullwinkle restore # change the ownership for restoration run, 755 perms already present
>
> deja-dup # Restore to /media/mint/BACKUP/restore
>
> Result is in /media/mint/BACKUP/restore/home/bullwinkle
> and includes lots of dot files, plus the usual things
> like a Pictures folder.
>
> The screenshot here, the details of how or what don't matter,
> this is just a quick listing to show what my restoration got me.
> It kinda looks like a home directory.
>
> [Picture]
>
> https://i.postimg.cc/SsXVX9WY/deja-dup-restore.gif
>
> Since my backup was a Full and there are no Incrementals,
> there is just the one tar.gz file containing my home directory.
> It's possible the marked file would open in Archive Manager,
> as an example.
>
> duplicity-full.20240305T012151Z.manifest
> duplicity-full-signatures.20240305T012151Z.sigtar.gz
> duplicity-full.20240305T012151Z.vol1.difftar.gz <=== 8 megabytes compressed
>
> If you did a Full backup on Sunday, an Incremental on Monday, an Incremental on Tuesday,
> to restore to Tuesday onto an external drive, Deja-dup would
>
> unzip the Full onto the output drive
> unzip Monday onto the output drive (replacing files with newer ones)
> unzip Tuesday onto the output drive (replacing files with newer ones)
>
> Done in an unintelligent way, this takes slightly more time, but isn't
> that bad all things considered. Some dedicated backup/restore programs
> would likely have a more efficient algorithm for deciding which
> files to grab from each of the tar.gz things.
>
> But the software doesn't exactly tell you what it's doing,
> and it is more opaque than I expected.
>
> bullwinkle@LMDE6TST:~$ apt search dirstat
> p k4dirstat - graphical disk usage display with cleanup
> p k4dirstat:i386 - graphical disk usage display with cleanup
> p qdirstat - Qt-based directory statistics
> p qdirstat:i386 - Qt-based directory statistics
>
> sudo apt install qdirstat # Because pulling in all of KDE isn't all that good
>
> sudo qdirstat /media/mint/BACKUP # Enumerate my destination drive, look for space wasters

Thanks for the info. I'll have a play later to see if I can get at those
restored files.

I put the "faulty" HD in a USB-SATA caddy but it seemed dead, as after 5
minutes my now live Mint 21.2 laptop couldn't find the HD. With nothing
to lose, I put it in the HD in the freezer for 2 hours and then tried
again. Success! I quickly (or as quickly as USB2 would allow...)
downloaded all the files to a USB stick.

II thought it now worth trying the HD back in the laptop to see if it
would boot. Of course it does, but as it is now unreliable, I'm getting
a new laptop which should arrive next week. I'll keep the old one as a
spare, occasionally booting and recharging (I've had it over 9 years,
and it was already 18 months old when I got it, so it's been good value.
My previous laptop, an HP61, lasted only just over 6 years).

--

Jeff

On 3/5/24 9:10 AM, Jeff Layman wrote:
> On 05/03/2024 02:36, Paul wrote:
>> On 3/4/2024 1:49 AM, Jeff wrote:
>>> Gordon <Gordon@leaf.net.nz> Wrote in message:r
>>>> On 2024-03-03, Jeff <jeff@invalid.invalid> wrote:> I've been trying
>>>> to restore a recent deja dup backup to an>  external storage device
>>>> (I've tried a 1TB HD and a USB stick) as>  I need to access some
>>>> files. I'm having to do this with an old >  DVD with a 17.2 iso on
>>>> it. The backup restore proceeds ok, and I>  can watch deja dup
>>>> write the files  to the external storage>  device. But I can't see
>>>> them with the iso's file manager! The>  folder has nothing in it,
>>>> but "properties" shows the device free>  memory decreasing and the
>>>> number of files increasing . I tried>  using the file manager with
>>>> elevated privileges, but although it> seems to appear I was not
>>>> asked for a sudo password, and no files>  were visible. Is this a
>>>> permission issue? If so, how do I get>  access to view the files?>>
>>>> This is necessary as the laptop's HD has suddenly become>
>>>> inaccessible by the Bios, and booting is not possible.>iso files
>>>> need to be mounted in order to see the files within.
>>>
>>> Why are you creating and iso?A restore should just list the files
>>>   as a directory which given the correctpermissions are readable
>>>   with a file manager, (or ls.)
>>>
>>> The Mint 21.3 on the laptop's HD is not accessible as the HD has
>>>   failed and I can't boot to it. I have now been able to boot to a
>>>   live 21.2 iso and can get to the deja dup backup of my Home
>>>   folder on a USB stick. I can "restore" the files on that to an
>>>   external HD but can't access them. I can't even see them on that
>>>   external HD using the live iso's file manager. It just reports
>>>   that the folder I restored to has 0 bytes! Yet I know the HD free
>>>   capacity has decreased by over 100 GB, so the files are on it.
>>>   How can I view them?
>>>
>>
>> I did a test restore here, using a random partition created in gparted.
>> And I didn't have permission to write to the top level, as
>> an ordinary user.
>>
>> cd /media/mint/BACKUP    # My new "external" drive in a virtualbox guest
>>                           # I could have made this just as easily
>> with fdisk and friends
>>
>> sudo mkdir restore       # Made my first directory as root
>>
>> sudo chown bullwinkle:bullwinkle restore    # change the ownership
>> for restoration run, 755 perms already present
>>
>> deja-dup                 # Restore to /media/mint/BACKUP/restore
>>
>> Result is in  /media/mint/BACKUP/restore/home/bullwinkle
>> and includes lots of dot files, plus the usual things
>> like a Pictures folder.
>>
>> The screenshot here, the details of how or what don't matter,
>> this is just a quick listing to show what my restoration got me.
>> It kinda looks like a home directory.
>>
>>     [Picture]
>>
>>      https://i.postimg.cc/SsXVX9WY/deja-dup-restore.gif
>>
>> Since my backup was a Full and there are no Incrementals,
>> there is just the one tar.gz file containing my home directory.
>> It's possible the marked file would open in Archive Manager,
>> as an example.
>>
>> duplicity-full.20240305T012151Z.manifest
>> duplicity-full-signatures.20240305T012151Z.sigtar.gz
>> duplicity-full.20240305T012151Z.vol1.difftar.gz        <=== 8
>> megabytes compressed
>>
>> If you did a Full backup on Sunday, an Incremental on Monday, an
>> Incremental on Tuesday,
>> to restore to Tuesday onto an external drive, Deja-dup would
>>
>>      unzip the Full onto the output drive
>>      unzip Monday onto the output drive  (replacing files with newer
>> ones)
>>      unzip Tuesday onto the output drive  (replacing files with newer
>> ones)
>>
>> Done in an unintelligent way, this takes slightly more time, but isn't
>> that bad all things considered. Some dedicated backup/restore programs
>> would likely have a more efficient algorithm for deciding which
>> files to grab from each of the tar.gz things.
>>
>> But the software doesn't exactly tell you what it's doing,
>> and it is more opaque than I expected.
>>
>> bullwinkle@LMDE6TST:~$ apt search dirstat
>> p   k4dirstat                       - graphical disk usage display
>> with cleanup
>> p   k4dirstat:i386                  - graphical disk usage display
>> with cleanup
>> p   qdirstat                        - Qt-based directory statistics
>> p   qdirstat:i386                   - Qt-based directory statistics
>>
>> sudo apt install qdirstat             # Because pulling in all of KDE
>> isn't all that good
>>
>> sudo qdirstat /media/mint/BACKUP      # Enumerate my destination
>> drive, look for space wasters
>
> Thanks for the info. I'll have a play later to see if I can get at
> those restored files.
>
> I put the "faulty" HD in a USB-SATA caddy but it seemed dead, as after
> 5 minutes my now live Mint 21.2 laptop couldn't find the HD. With
> nothing to lose, I put it in the HD in the freezer for 2 hours and
> then tried again. Success! I quickly (or as quickly as USB2 would
> allow...) downloaded all the files to a USB stick.
>
> II thought it now worth trying the HD back in the laptop to see if it
> would boot. Of course it does, but as it is now unreliable, I'm
> getting a new laptop which should arrive next week. I'll keep the old
> one as a spare, occasionally booting and recharging (I've had it over
> 9 years, and it was already 18 months old when I got it, so it's been
> good value. My previous laptop, an HP61, lasted only just over 6 years).
>
Where did you get the idea to put the drive in the freezer?

On 3/5/2024 10:15 AM, Nic wrote:
> On 3/5/24 9:10 AM, Jeff Layman wrote:

>> Thanks for the info. I'll have a play later to see if I can get at those restored files.
>>
>> I put the "faulty" HD in a USB-SATA caddy but it seemed dead, as after 5 minutes
>> my now live Mint 21.2 laptop couldn't find the HD. With nothing to lose, I put it
>> in the HD in the freezer for 2 hours and then tried again. Success! I quickly (or
>> as quickly as USB2 would allow...) downloaded all the files to a USB stick.
>>
>> II thought it now worth trying the HD back in the laptop to see if it would boot.
>> Of course it does, but as it is now unreliable, I'm getting a new laptop which
>> should arrive next week. I'll keep the old one as a spare, occasionally booting and
>> recharging (I've had it over 9 years, and it was already 18 months old when I got it,
>> so it's been good value. My previous laptop, an HP61, lasted only just over 6 years).
>>
> Where did you get the idea to put the drive in the freezer?

That idea has been around for a long time.

https://www.pcworld.com/article/419677/that-old-freezer-trick-to-save-a-hard-drive-doesnt-work-anymore.html

"In 2007, we listed the 'freezer trick' as one of the solutions to revive a failed hard drive."

According to that article, the intent was for reversing stiction. Old drives (my 250MB Quantum Fireball
perhaps), the heads stay on the platter at shutdown, in a landing zone. And whether the
zone is "patterned" or "flat", the head can stick to the surface. We used to free those,
by giving the side of the HDA a "rap" with the yellow handle of a screwdriver (using
the screwdriver as a hammer, in essence).

The freezer trick, according to PCWorld, was for that too.

Modern drives have landing ramps, so the heads no longer park
on the platter. Only if the landing sequence fails and there
is not sufficient rotational energy to finish the sequence,
do the heads end up on the platter. And yes, if that happens,
a modern head will stick to the platter. The platter is ultra-smooth
and inviting for stiction. But normally, the heads trundle over to the
plastic landing ramp. And a stiction event just isn't possible.

If the hard drive had a Supercap and power converter, it could
have an even more reliable source of energy for an emergency
head retract.

On a laptop drive, with say a single platter, there isn't
a lot of rotational inertia. That means the emergency
landing sequence doesn't have a lot of margin for landing.
Turning the motor into a generator, does not yleid a lot
of power to move the heads to the ramp.

I have a dead Barracuda 32550N, from before the year 2000.
It is a 2GB drive with *six* platters. And it happens to have
no landing ramp. The direction of rotation is the reverse of
a modern drive. Now, I just checked it, and the heads are "loose"
on the platter. No stiction evident. All these years, it did not
stick. The finish is also weird. It looks nickel-plated.
And if you hold the drive on edge, the platter may not actually
be mirror-flat. It must have had a significant flying height.

So while modern drives have a landing ramp, and should not
need the freezer (as described on PCWorld above), in the circumstance
of a laptop drive with a single platter, there's a risk one of
those could land the heads in the wrong place. And then the freezer
treatment might still work -- even though it's the wrong era to be
doing that.

At the beginning of the ramp era, they may not have known
about Supercaps. But they certainly could have switched to
that, and especially if the engineering equations indicated
a single platter laptop drive, didn't have the necessary energy
(in generator mode).

I found a thread about a week ago, where someone said to turn
the three phase hard drive motor into a generator, there's an
"H-bridge setting" for the mode, and then there might be
substrate diodes in there that produce pulsating DC as the
motor spins slower and slower. And that energy is used to run
the voice coil. On drives with lots of platters, you might even
have a tiny bit of energy left over.

Paul

On 05/03/2024 15:15, Nic wrote:

>> I put the "faulty" HD in a USB-SATA caddy but it seemed dead, as after
>> 5 minutes my now live Mint 21.2 laptop couldn't find the HD. With
>> nothing to lose, I put it in the HD in the freezer for 2 hours and
>> then tried again. Success! I quickly (or as quickly as USB2 would
>> allow...) downloaded all the files to a USB stick.
>>
>> II thought it now worth trying the HD back in the laptop to see if it
>> would boot. Of course it does, but as it is now unreliable, I'm
>> getting a new laptop which should arrive next week. I'll keep the old
>> one as a spare, occasionally booting and recharging (I've had it over
>> 9 years, and it was already 18 months old when I got it, so it's been
>> good value. My previous laptop, an HP61, lasted only just over 6 years).
>>
> Where did you get the idea to put the drive in the freezer?

In addition to Paul's reply, I would add that the other component of a
HD is the control electronics. When this goes wrong, you're in a much
trouble as with a mechanical fault. The freezer trick can help with, for
example, a faulty resistor which overheats. Let's say it goes high when
it reaches 60°C; well, it will take a lot longer to go from -18°C to
60°C than from room temp at 20°C. During that time the HD might be fully
operational.

I first used the freezer trick almost 20 years ago. I was in business
then, and had a quite hi-spec desktop running Windows XP. One day it
wouldn't boot, and I could hear the "click of death". I can't remember
if it even got as far as a BSOD - the disk might have failed completely.
A bit of searching led me to the freezer idea. It worked for a while, as
the first time I got about 15 minutes of access to get at critical
files. On trying again, I got about 8 minutes, then just a couple. But
it was enough to get to the important stuff. After that, the disk was
irretrievably dead.

An amusing aside to this is that, for once, Murphy's Law failed. I'd
bought the computer with an extended guarantee for 3 years on-site
service. The HD failed at 2 years and 11 months! It took the computer
technician all morning to get it running again, as there was quite a bit
of software to install and check.

--

Jeff

On 3/6/2024 2:47 AM, Jeff Layman wrote:
> On 05/03/2024 15:15, Nic wrote:
>
>>> I put the "faulty" HD in a USB-SATA caddy but it seemed dead, as after
>>> 5 minutes my now live Mint 21.2 laptop couldn't find the HD. With
>>> nothing to lose, I put it in the HD in the freezer for 2 hours and
>>> then tried again. Success! I quickly (or as quickly as USB2 would
>>> allow...) downloaded all the files to a USB stick.
>>>
>>> II thought it now worth trying the HD back in the laptop to see if it
>>> would boot. Of course it does, but as it is now unreliable, I'm
>>> getting a new laptop which should arrive next week. I'll keep the old
>>> one as a spare, occasionally booting and recharging (I've had it over
>>> 9 years, and it was already 18 months old when I got it, so it's been
>>> good value. My previous laptop, an HP61, lasted only just over 6 years).
>>>
>> Where did you get the idea to put the drive in the freezer?
>
> In addition to Paul's reply, I would add that the other component of a HD is the control electronics. When this goes wrong, you're in a much trouble as with a mechanical fault. The freezer trick can help with, for example, a faulty resistor which overheats. Let's say it goes high when it reaches 60°C; well, it will take a lot longer to go from -18°C to 60°C than from room temp at 20°C. During that time the HD might be fully operational.
>
> I first used the freezer trick almost 20 years ago. I was in business then, and had a quite hi-spec desktop running Windows XP. One day it wouldn't boot, and I could hear the "click of death". I can't remember if it even got as far as a BSOD - the disk might have failed completely. A bit of searching led me to the freezer idea. It worked for a while, as the first time I got about 15 minutes of access to get at critical files. On trying again, I got about 8 minutes, then just a couple. But it was enough to get to the important stuff. After that, the disk was irretrievably dead.
>
> An amusing aside to this is that, for once, Murphy's Law failed. I'd bought the computer with an extended guarantee for 3 years on-site service. The HD failed at 2 years and 11 months! It took the computer technician all morning to get it running again, as there was quite a bit of software to install and check.
>

One of the flaws in disk drives, was a certain motor controller IC
had some sort of power dissipation issue. On Maxtor drives, the
chip would actually burn out, rendering all data lost... until
you swapped out the controller board. the disks back then
didn't have FDE crypto, so there was no EEPROM to move from
one controller board to another.

Normally, the rate that things heat up, is rather quick.
Only if the HDA (chunk-o-aluminum) is the temperature-dependent
part, would freezer treatment be keeping the temperature low
enough for the job. Drives work up to 60C or so. The write
current and other settings, may be temperature dependent and
the drive has to adjust conditions as it sees them. This means
that the addition of a temperature sensor, was for more than
cosmetic reasons.

These are some of the sensor types. Some drives report a bogus (fixed)
value for temperature, which means the firmware isn't sharing the
info with us. A bogus temperature is not always 0xFF like you would expect.

Temperature sensor
Shock sensor <=== why your RMA was rejected (a "drive abuse detector")
Drop sensor <=== only on a limited number of laptop drives, "park heads before impact"
Helium pressure <=== only on Helium drives, air breathers operate at atmospheric pressure
Data recovery could be more difficult with Helium...

Paul