dCorePlus-bionic64.iso Kernel Panic and solution (bug?)

[tinyyoyo]

Hi, Adam here, long time lurker, first time poster.

The TL;DR
    Setup: dCorePlus-bionic64.iso(MD5 verified) as VirtualBox(5.2.10_Ubuntu r121806) guest, Lubuntu 18.04 Host(Live Session).
    Problem: At vm boot time, was throwing: "Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,1)"
    Solved: By passing: root=sr0 , as a boot parameter.
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I recently downloaded the ubuntu based 64bit version of dCore, link: http://tinycorelinux.net/dCore/x86_64/release/dCore-bionic64/dCorePlus-bionic64.iso
    to check out the latest state of development.

Upon booting the .iso as a vm in VirtualBox, I kept getting a kernel panic, so first things first, I checked the md5 hash of the .iso file, exact match.
    link: http://tinycorelinux.net/dCore/x86_64/release/dCore-bionic64/dCorePlus-bionic64.iso.md5.txt

So then I did some basic searching for "Kernel panic - not syncing: VFS" and found this:
    link: https://askubuntu.com/questions/41930/kernel-panic-not-syncing-vfs-unable-to-mount-root-fs-on-unknown-block0-0
    (scroll to the bottom, last answer)

While it did not have a direct answer, I noticed I was not getting as many boot messages as I was seeing in various search results,
   and by chance I had mounted the .iso file and was looking at the isolinux.cfg boot stanza, and saw " loglevel=3 " set a default,

So then I booted the .iso in VirtualBox passing "dc loglevel=4" at the boot: prompt, woohoo! more kernel messages,
    but not enough to see what I was looking for, namely, the root device the Kernel panic was telling me it could not find.(hint: the mounted .iso)

Setting "dc loglevel=5" did the trick, I was presented with this:

(See attached png)

I could see on line 2, that a root device of "(null)" just wasn't going to satisfy my needs(or the kernel),
    and line 3 helpfully instructs to append a valid root device.
    and near the bottom, a device named "sr0", which I knew was the root device(cdrom) the kernel was looking for and could not find.

So armed with the knowledge that I could append kernel parameters at the "boot:" prompt, I dutifully appended "root=sr0" at the "boot:" prompt
    and 2 seconds later(I love TC) I was looking at a flwm desktop.

Now, I don't know if this is a special case of running as a vm in VirtualBox, or something else, but I see it as bug, or at the very least a mis-configuration.

Any Thoughts?

[Jason W]

Hi Adam.  I just now have booted dCorePlus-bionic64.iso, md5sum is c3f135a45072fd7605d5bc303b7207a2, in  dCore-stretch64 with it's Virtualbox version 5.1.30.  As well as on a Ubuntu Bionic 64 bit HD install with it's Virtualbox version 5.2.10 with no issues, going straight into an X session with flwm_topside window manager. 

What amount of RAM did you give the Virtualbox session during setup?  Since this is dCorePlus, I recommend at least a gig of it.  I allocated about 1.5G of RAM in my Virtualbox setup.  I have seen similar errors in the past when there was not enough RAM.  dCorePlus images are up to 300MB to allow all drivers and firmware available, and upon decompressing on boot that will take up quite a bit of space.   

[tinyyoyo]

Hi Jason, thanks for the speedy reply.

As soon as I saw your 1.5gig ram suggestion, I increased the amount I had allocated from 1gig to 1.5gig.

You were right, flawless boot.

What is interesting to me is the failure mode, It did not occur to me it may be ram shortage.

Is there a standard place in the wiki/forum that info like this is stored? Maybe part of the release notes, or the Plus images category?

If not, I would like to contribute somehow by adding to, or creating some relevant wiki page.

Thank you,

Adam

[Jason W]

Hi Adam.  It would be good to have this piece of info in the wiki, esp as dCorePlus is aimed at folks new to dCore who are doing an initial install.

If you would be so kind as to add a wiki entry on this dCorePlus subject, it would be appreciated. 

[Rich]

Hi tinyyoyo
You can use your forum username and password to login to the Wiki.

[tinyyoyo]

Thanks Rich,
    I discovered I could login to the wiki right after I got a forum account.

Jason,
    I will more fully familiarize myself with the wiki as it now is,
    and take my time to make sure any additions are well thought out.

Thanks,

Adam

[Rich]

Hi tinyyoyo

I discovered I could login to the wiki right after I got a forum account.

It was a preemptive answer on my part. Most people ask how to login in when it comes to altering the Wiki.

[nour]

Hi Jason, thanks for the speedy reply.

As soon as I saw your 1.5gig ram suggestion, I increased the amount I had allocated from 1gig to 1.5gig.

You were right, flawless boot.

What is interesting to me is the failure mode, It did not occur to me it may be ram shortage.

Is there a standard place in the wiki/forum that info like this is stored? Maybe part of the release notes, or the Plus images category?

If not, I would like to contribute somehow by adding to, or creating some relevant wiki page.

Thank you,

Adam

I though tinyCore is "small" as its name suggesses but 1.5 gig is a lot so no hope to install it on an old PC that havs 2 gig.

[Jason W]

dCore does not need 1.5G of RAM to run, only dCorePlus does.  dCorePlus images have a lot of extras to allow new users full hardware and networking support to get set up with.  And what requires so much RAM is the dCorePlus image along with it's large extension is copied to RAM during boot.  The reason for copying to RAM is so the dCorePlus image can be burned with the dd command to a USB and not just to a CD.  And also so that dCore-usbinstall can use that same USB to install to when booted.  Users of machines that have limited resources would need to use standard dCore and download the premade SCEs for wireless.  And then import what is needed.  dCorePlus provides a turnkey solution to make the setup process easier. 

dCore-wheezy.gz is about 8.5MB, and uncompressed is about 17MB worth of files.  Most other dCore images are about 15MB compressed size. 

A 2 gig of RAM machine would be more than enough to install and use any Tinycore or dCore offerings.