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[SOLVED] Kernel not opening root device
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rurouni_hou_ou
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PostPosted: Sat Aug 30, 2014 6:04 pm    Post subject: [SOLVED] Kernel not opening root device Reply with quote

I am 'fresh' installing Gentoo and I have not been able to boot my kernel because of a kernel panic.

The error message on boot is here.

So I've been repeatedly being re-configuring and re-compiling the kernel with additions of drivers for SATA and the file systems used on the disk. I've also made sure that these drivers have been build-in to the kernel.

The code for the .config is also on the same page.

The kernel command line is as follows for grub:
Code:
/vmlinuz-3.14.16-gentoo root=/dev/sda4 ro init=/usr/lib/systemd/systemd


And the parttion table too:
Code:
/dev/sda1    bios_grub
/dev/sda2    ext2    /boot
/dev/sda3    swap
/dev/sda4    ext4    /
/dev/sda5    ext4    /home


Any help whatsoever, I would be grateful for as I'm a little tired from a couple of day's worth of compiling :)


Last edited by rurouni_hou_ou on Sun Aug 31, 2014 7:51 pm; edited 1 time in total
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py-ro
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PostPosted: Sat Aug 30, 2014 7:00 pm    Post subject: Reply with quote

You are probably missing GUID Partition Table (GPT) Support, since the kernel sees only sda1, which should be the protective MBR.

Can't open your config, it says Access Denied.

Bye
Py
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rurouni_hou_ou
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PostPosted: Sun Aug 31, 2014 10:44 am    Post subject: Reply with quote

py-ro wrote:
You are probably missing GUID Partition Table (GPT) Support, since the kernel sees only sda1, which should be the protective MBR.

Can't open your config, it says Access Denied.

Bye
Py


Thanks for the reply and EFI GPT support was not enabled but this did not work when enabled. I also added the command line support too and still did not work. The link seems to be working now for the config.
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NeddySeagoon
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PostPosted: Sun Aug 31, 2014 12:28 pm    Post subject: Reply with quote

rurouni_hou_ou,

Boot with the liveCD or whatever and get into your chroot.
Now lets check the date and time on your kernel files.

Oldest should be /usr/src/linux/.config look with ls -l
This is the file that starts it all.

Next should be /usr/src/linux/arch/x86/boot/bzImage
Its made using the .config above, so if its not newer, we know that your kernel was not built from that .config.

Lastly, look at your kernels in /boot
There should be one there with the same timestamp. If all is in order you have built you kernel and put it into /boot but are you actually using it?

Make a note of the full file name, nom look in your boot loader configoration file. Is it loading the kernel you actually need.


"did not work" is not a useful error report. What error message did you get?
There are lots of ways for it to not work, even after your GPT disk label is fixed.
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Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.
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rurouni_hou_ou
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PostPosted: Sun Aug 31, 2014 1:52 pm    Post subject: Reply with quote

NeddySeagoon,

I understand and apologize that was a little rude.

I have looked at the time-stamps and the kernel was compiled with the latest .confg and install to /boot with the correct kernel.

I have rebooted and looked at the printk messages again and they report:
Code:
VFS: cannot open root device "sda4" or unknown-block(0,0)

Now, I must say that I did remove some ahci drivers because I though they were not needed for my drive, but a quick search on the net brought up this. It discuses ahci drivers. This may be my fault for un-dooing the fix py-ro posted with removing ahci drivers. I shall re-compile and re-install and report back.

Thank you,
rurouni_hou_ou
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NeddySeagoon
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PostPosted: Sun Aug 31, 2014 3:29 pm    Post subject: Reply with quote

rurouni_hou_ou

unknown-block(0,0) means that the kernel cannot see your HD at all.

Previously, it was unknown-block(8,4) and a list of block devices the kernel could see.
At least that told that the kernel could see your HDD at that time.

One of the low level hard drive chipset drivers, such an ahci, is a good bet.
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fernan82
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PostPosted: Sun Aug 31, 2014 4:18 pm    Post subject: Reply with quote

An easy way to know which drivers you need to compile is to boot the live cd and run lspci -k.
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rurouni_hou_ou
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PostPosted: Sun Aug 31, 2014 7:50 pm    Post subject: Reply with quote

I was able to locate the missing driver: SCSI disk support, it was compiled as a module. I was too busy looking under Serial ATA and Parallel ATA drivers.

Thanks guys!
rurouni_hou_ou
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NeddySeagoon
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PostPosted: Sun Aug 31, 2014 8:02 pm    Post subject: Reply with quote

rurouni_hou_ou,

Well done. On to your next Gentoo learning experience.
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