[Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Discussions about using Linux guests in VirtualBox.
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DonJuan
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Joined: 1. Oct 2018, 11:15

[Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by DonJuan »

I have Virtualbox 5.2.18 installed on a Windows 10 host.
Several VMs running different flavours of Linux (Debian, Centos).

I booted some one of these VMs (Debian, Centos) via a Linux Live CD/DVD (I used Knoppix and Partedmagick).
Then I wanted to mount a hard disk partition of the existing VM installation.
"fdisk -l" showed me /dev/sda1, /dev/sda2, ...
The Linux system is installed on /dev/sda1, therefore I issued the command:
mount /dev/sda1 /mnt

I got the error:
mount: wrong fs type, bad option, bad superblock, ...

Giving the fs type:
mount -t ext4 /dev/sda1 /mnt
did not help. Same error message.

I should mention that the Linux systems within the VMs run fine.
There definitively are ext4 file systems on each /dev/sda1
Last edited by socratis on 2. Oct 2018, 17:46, edited 1 time in total.
Reason: Marked as [Invalid].
socratis
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Posts: 27330
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Re: Unable to Mount Existing HD when Booting via Live CD/DVD

Post by socratis »

You can't access your host's partitions. "/dev/sda1" of your host has no meaning in a VM, it doesn't have a clue about it. And that's a good thing™. Think of your VM as a different computer (which it is). It can't have access to your host's resources, not directly, not easily.
Do NOT send me Personal Messages (PMs) for troubleshooting, they are simply deleted.
Do NOT reply with the "QUOTE" button, please use the "POST REPLY", at the bottom of the form.
If you obfuscate any information requested, I will obfuscate my response. These are virtual UUIDs, not real ones.
DonJuan
Posts: 10
Joined: 1. Oct 2018, 11:15

Re: Unable to Mount Existing HD when Booting via Live CD/DVD

Post by DonJuan »

Well, let me clarify it:
I do not intend to access a hard disk partition of my host, but a hard disk partition of the guest within the VM.
I start the Live CD within the same VM as of my Linux guest. I do see its hard disk and its partitions and thus I expect to be able to mount it.
mpack
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Re: Unable to Mount Existing HD when Booting via Live CD/DVD

Post by mpack »

VirtualBox has no knowledge of or control over partitions etc inside the guest. That is entirely the business of the guest OS.
socratis
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Location: Greece

Re: Unable to Mount Existing HD when Booting via Live CD/DVD

Post by socratis »

I'm sorry, I misread your original message. Reading it again after the clarification made it crystal clear. Mea culpa... :?

But as mpack said, that's not a VirtualBox problem. Marking as [Invalid].
Do NOT send me Personal Messages (PMs) for troubleshooting, they are simply deleted.
Do NOT reply with the "QUOTE" button, please use the "POST REPLY", at the bottom of the form.
If you obfuscate any information requested, I will obfuscate my response. These are virtual UUIDs, not real ones.
DonJuan
Posts: 10
Joined: 1. Oct 2018, 11:15

Re: [Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by DonJuan »

I am sorry but I don't agree that this is an invalid topic.
I am within the virtual machine and thus within the guest system, not outside.
I simply chose a different boot device (CD) instead of booting the installed system.

@mpack
You said:
VirtualBox has no knowledge of or control over partitions etc inside the guest.
That is not true when I am within the virtual machine.
I do see the (guest) partitions from within the virtual machine. I see them after having booted the installed system (obiously, otherwise I could not have booted it),
and I see them, too, when booting the Live CD.
However I cannot mount them in the latter case.
Martin
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Re: [Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by Martin »

- Your live CD is booting - VBox is working correctly.
- Your live CD sees the partitions inside the virtual harddisk - VBox is working correctly.
- Your live CD has a problem handling the parations inside the correctly working virtual harddisk - not a VBox problem.
DonJuan
Posts: 10
Joined: 1. Oct 2018, 11:15

Re: [Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by DonJuan »

- Your live CD is booting - VBox is working correctly.
- Your live CD sees the partitions inside the virtual harddisk - VBox is working correctly.
Correct.
- Your live CD has a problem handling the parations inside the correctly working virtual harddisk - not a VBox problem.
That Knoppix Live CD never had and has any problems accessing ext4 Linux hard disk partitions in non-virtualized installations.
You say that this is not a VBox problem - I do not see that Knoppix is broken.
So: Whose problem is it?
mpack
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Posts: 39156
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Re: [Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by mpack »

Well then, let's get specific. Which virtual hardware mechanism do you believe has failed? E.g. is the guest OS no long able to read the drive?
socratis
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Re: [Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by socratis »

DonJuan wrote:I am within the virtual machine and thus within the guest system, not outside.
So, if I choose to remove my /usr/bin from my virtual hard drive, does this make it a VirtualBox problem? Of course it doesn't!

Just because an OS/program that runs in the context of VirtualBox has a problem, it doesn't make it a VirtualBox problem necessarily. You're having an issue that has most probably nothing to do with VirtualBox, so my suggestion would be to treat it as such, as a native problem with the OS or the application of the guest.
DonJuan wrote:That Knoppix Live CD never had and has any problems accessing ext4 Linux hard disk partitions in non-virtualized installations.
Try GParted. Try another LiveDVD. Maybe the filesystem in the VM is corrupted, who knows...

Oh, I know who doesn't know, who doesn't have a clue about your filesystem: VirtualBox.
Do NOT send me Personal Messages (PMs) for troubleshooting, they are simply deleted.
Do NOT reply with the "QUOTE" button, please use the "POST REPLY", at the bottom of the form.
If you obfuscate any information requested, I will obfuscate my response. These are virtual UUIDs, not real ones.
DonJuan
Posts: 10
Joined: 1. Oct 2018, 11:15

Re: [Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by DonJuan »

I owe you the solution:

Both Live CDs I used were too old. The EXT4 filesystem was further developed in the meantime which made it impossible for the old Live CDs to mount such a (newer) file system.
A newer Knoppix version or the rescue system from the Debian Installer CD worked.
So it was my fault using those old systems.

Nevertheless: Thanks a lot for your help.
socratis
Site Moderator
Posts: 27330
Joined: 22. Oct 2010, 11:03
Primary OS: Mac OS X other
VBox Version: PUEL
Guest OSses: Win(*>98), Linux*, OSX>10.5
Location: Greece

Re: [Invalid] Unable to Mount Existing HD when Booting via Live CD/DVD

Post by socratis »

DonJuan wrote:I owe you the solution:
A really impressively rare quality these days. Kudos!
DonJuan wrote:A newer Knoppix version or the rescue system from the Debian Installer CD worked.
Glad you got it going.

I have a weekly task where I check my 7-8 favorite LiveDVDs for updates. I just have them bookmarked inside a folder which then I use the "Open in Tabs" feature of my browser... ;)
Do NOT send me Personal Messages (PMs) for troubleshooting, they are simply deleted.
Do NOT reply with the "QUOTE" button, please use the "POST REPLY", at the bottom of the form.
If you obfuscate any information requested, I will obfuscate my response. These are virtual UUIDs, not real ones.
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