What causes the error: Unknown filesystem: grub rescue

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What causes the error: Unknown filesystem: grub rescue

Postby cox123456 » 2018-08-28 09:38

I'm running Debian Wheezy on an embedded hardware for IoT.

For any reason I got twice the following problem in a few days:

Code: Select all
Unknown filesystem
grub rescue:

I know how to recover from that error, but I don't know what may be causing the error. As my unit operates in the field with difficult access, this type of error is very difficult for us to recover.

Is this a harwdare problem? Anything wrong with my SSD? A power off? A power off when something is being written to disk?

How can I check my disk integrity? How to avoid that problem in the future ?

Thanks for helping.
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Re: What causes the error: Unknown filesystem: grub rescue

Postby bw123 » 2018-08-28 11:23

...
Is this a harwdare problem? Anything wrong with my SSD? A power off? A power off when something is being written to disk?

How can I check my disk integrity? How to avoid that problem in the future ?
...


I guess it could be a hardware problem, but you are the one with access to the machine and the logs. Yes I don't think power off while disk is being written to is a good idea. The first check I would make is logfiles for any IORDY errors or such, then install pkg smartmontools and use it. If it passes for health, then I'd suspect filesystem error or grub installation error of some sort.

Back it up.

https://duckduckgo.com/html/?q=linux+ch ... +integrity
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Re: What causes the error: Unknown filesystem: grub rescue

Postby p.H » 2018-08-28 14:11

bw123 wrote:I know how to recover from that error, but I don't know what may be causing the error.

How do you recover ?
This error happens when GRUB can see the partition or volume defined in the variable $prefix which is supposed to contain /boot/grub, but fails to recognize its filesystem.
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Re: What causes the error: Unknown filesystem: grub rescue

Postby Head_on_a_Stick » 2018-08-29 05:04

I suffer from depression and may lash out occasionally, try not to take it personally.
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Re: What causes the error: Unknown filesystem: grub rescue

Postby cox123456 » 2018-08-31 12:21

Thanks for the replies. Just to make clear my question:

I know how to recover from the error and I know what this error is about. What I don't know is the incident that may cause this error. Let me better explain.

That Debian is installed on a embedded computer, that will be installed in the field in a IoT system with difficult access. The system transmits data to our cloud servers using 3G connection, so there is no way to connect to them remotelly. So, if some unit fails (or does not boot), we need to take a truck and drive almost 4 hours for maintenance.

We got this error in one unit and I really need to know the possible causes. If this seens to be SSD disk, connection fail or hardware fail, fine. Once we get this error we exchange the unit for a new one and life goes on. If this error may be caused by software, we need to have hints of the possible causes to debug our software and make sure it disappears in the next released version.

So, thanks for any reply. All things I've read till now says how to recover from the error, not indicating the its possible causes.
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Re: What causes the error: Unknown filesystem: grub rescue

Postby p.H » 2018-08-31 13:04

Telling how you recover may help us find the cause of the error.
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Re: What causes the error: Unknown filesystem: grub rescue

Postby bw123 » 2018-08-31 14:32

...
So, thanks for any reply. All things I've read till now says how to recover from the error, not indicating the its possible causes.
...


Well, the link that HoaS posted says this,
...
However, any problem that leaves you in the rescue shell probably means that GRUB was not correctly installed.
...


If it's not hardware, then it must be software, right? Are there any indications of hardware error in the logs? If not, then it's something else. It doesn't matter how many hours it takes you to get to the unit to repair it. What matters is gathering info and eliminating possibilities.

It's not realistic to ask, "What is every possible thing that could cause this to happen?" It is more realistic to ask, what evidence is available that would show what caused the error in this particular case?
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Re: What causes the error: Unknown filesystem: grub rescue

Postby GarryRicketson » 2018-08-31 16:34

A power off, not shutting down correctly, could cause it, Does this happen every time you re-boot, ?
But there are many other things or events that could cause it, why have you not looked at the logs, to try to see if they show anything ?
There are many things in your posts that are not making sense to me :
So, if some unit fails (or does not boot), we need to take a truck and drive almost 4 hours for maintenance.

and
That Debian is installed on a embedded computer, that will be installed in the field ---snip--

"will be installed in the field", implies it has not yet been installed in the field, yet above , the OP say they have to take a truck, and drive 4 hours, for maintenance,
The system transmits data to our cloud servers using 3G connection, so there is no way to connect to them remotelly.

That seems just plain foolish, if it is "transmitting" to some kind of cloud server, why don't you use ssh to access, it ?
To have a remote system, and not even have ssh access to it, just does not make sense to me,
How can I check my disk integrity?

There are many tools available to do that, why have you not done any searches, and tried some ?
Are you really the administrator of this system ? or just the "owner",It sounds to me like you need to find a qualified person / tech to help you set up this remote system, and administer it for you, if you work with them, they can show you how and what they do, also keep notes, so that once you understand the
procedures, you can do these things, perform maintenance, trouble shoot,etc...
If there is any doubt that the drive is good, then by all means replace it with a good one,
I know how to recover from the error and I know what this error is about.

This makes the least amount of sense, if you know what the error is about, WHY are you asking us ?
You have not provided 1 shred of clues, error logs, etc, and there seem to be a lot of details about this you are not telling us,... I can't help but wonder, why on earth you are using a unsupported, out of date version of Debian this, especially since it is in a remote location, and not easy to access physically,...
It seems like it would be essential to use a reliable, supported Debian version,
or maybe even another OS, I do understand some of the problems with the newer versions of Debian, and as much as I like to support Debian, and do think it is a good OS, if you feel you must use Debian 7 (wheezy), it might be better to look into some other options, that are current, maintained, and supported by the developers.
I have 1 Debian 7 server, and actually know of some sites that are still using Debian 6, (squeeze), how ever even though my server (and many others ) are
in a remote location, we do have someone actually there, on the server farm, that some one is a skilled administrator/tech, and is there to take care of the machines, and handle anything that requires some one with physical access.
Any way, Debian is reliable enough, but another think I don't understand, after your system is booted and running, Why or how does it get shutdown, or need to re-boot, I mean, it sounds rather ridicules to me the setup you have.
You have no remote access, ? Years ago I had several remote ham radio stations, 1 legal requirement for that is that one has the means to shutdown the station , in case something goes wrong and it starts transmitting unwanted signals, or something. I had it set up to where I could access, and turn off the power supply, via a radio transmission, I could also access the computer via radio transmission, of course if the power was shut off, even the computer could not be accessed,... sorry to be rambling,... any way what we need here is a lot more / better details on your system, and if you do not understand what your logs show, shows us what they have, maybe some one here will be able to see what caused the file system to get damaged, so that it is not readable,or fails to recognize its filesystem, Unknown filesystem.
Some times, just running 'fsck' manually can repair this, in fact it seems like it would be a good idea to have this "embedded" system run fsck , every time it boots,
Code: Select all
man fsck
, and check for any errors,... ok well sorry about the ToLong of a post,... Since nobody here has access to your system, it is rather difficult, if not impossible to diagnose, and tell you what is causing the errors, there are to many different things that could cause this.
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Re: What causes the error: Unknown filesystem: grub rescue

Postby pcalvert » 2018-08-31 17:09

You could try using LILO instead of GRUB. In some situations it seems to work better than GRUB.

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Re: What causes the error: Unknown filesystem: grub rescue

Postby GarryRicketson » 2018-08-31 17:42

You might be right on that, I was just reading some things about grub2,
another factor, but the OP does not tell us anything, nor show any config files,
But depending on where Grub2 was installed, could be the cause of the problem.

Another thing that does not make sense:
Looking at the OP again,...
cox123456 » Is this a harwdare problem?

Now, I ask, how on earth can anyone tell you if it is a hardware problem,
which it could be, but you do not even tell us what kind of hardware it is ?

And I can't help but wonder, if this is a embedded system, why the OP even feels they need to use Grub2, or any other boot loader, for that matter.
Is Debian, or Linux not capable of booting on it's own ?
I believe it is, unless there is something wrong with the "unknown hardware", or it's ssd.
from:ftp://www-uxsup.csx.cam.ac.uk/pub/doc/suse/suse9.0/adminguide-9.0/node8.html
The simplest boot concept involves only one machine with one operating system installed. The boot process for this case has already been outlined. The same boot concept can be used for a Linux-only machine. In this case, you could theoretically skip the installation of LILO or GRUB.

YES, let's K.I.S.S, "Keep It Simple Simon" Simon says.

On OpenBsd, and Minix3 we do not use grub or lilo, in a embedded system, with only 1 OS, a boot loader should not be needed,..
For embedded system Minix3 is my choice, but that would be another topic.
sorry
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