No or empty root= argument

abrinister · 05-01-2011, 09:36 AM

Hello all. I just compiled the 2.6.38.4 kernel and was booting it and I got a "No or empty root= argument". Then, I boot into my other kernel and check out my grub menu.lst and there is indeed a root= argument. It says:

Code:

ro root=/dev/mapper/vg0-ROOT

Menu.lst:

Code:

#boot=/dev/sda
default=2
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title Fedora (2.6.38.4)
	root (hd0,0)
	kernel /vmlinuz-2.6.38.4 ro root=/dev/mapper/vg0-ROOT rd_LVM_LV=vg0/ROOT rd_LVM_LV=vg0/SWAP rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
	initrd /initramfs-2.6.38.4.img
title Fedora (2.6.39-rc5)
	root (hd0,0)
	kernel /vmlinuz-2.6.39-rc5 ro root=/dev/mapper/vg0-ROOT rd_LVM_LV=vg0/ROOT rd_LVM_LV=vg0/SWAP rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
	initrd /initramfs-2.6.39-rc5.img
title Fedora (2.6.35.12-90.fc14.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.35.12-90.fc14.x86_64 ro root=/dev/mapper/vg0-ROOT rd_LVM_LV=vg0/ROOT rd_LVM_LV=vg0/SWAP rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
	initrd /initramfs-2.6.35.12-90.fc14.x86_64.img
title Fedora (2.6.35.12-88.fc14.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.35.12-88.fc14.x86_64 ro root=/dev/mapper/vg0-ROOT rd_LVM_LV=vg0/ROOT rd_LVM_LV=vg0/SWAP rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
	initrd /initramfs-2.6.35.12-88.fc14.x86_64.img
title Fedora (2.6.35.11-83.fc14.x86_64)
	root (hd0,0)
	kernel /vmlinuz-2.6.35.11-83.fc14.x86_64 ro root=/dev/mapper/vg0-ROOT rd_LVM_LV=vg0/ROOT rd_LVM_LV=vg0/SWAP rd_NO_LUKS rd_NO_MD rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet
	initrd /initramfs-2.6.35.11-83.fc14.x86_64.img
title Other
	rootnoverify (hd2,0)
	chainloader +1

plpl303a · 05-01-2011, 05:15 PM

I notice your root partitions are all on LVM volumes. Might the newly compiled kernel be missing LVM (or have it compiled as a module)?

abrinister · 05-01-2011, 07:14 PM

Yea I was thinking the same thing. But if you notice, I compiled the 2.6.39-rc5 kernel as well. While compiling, I missed the "make *config" step because I just wanted the generic modules. That kernel boots fine. The one I'm trying to get to work is 2.6.38.4, which I edited heavily with "make gconfig", the gtk config program. I didn't see anything for LVM in there, but its worth to look. I'll post back after recompile.

Thanks

Alex

abrinister · 05-01-2011, 08:51 PM

Well, I recompiled with different modules (mostly just an array of file systems support)(none of which are LVM since there is no option for it) now it gives me an

Code:

Error 253: Error parsing number

or something to that effect. Maybe it has something to do with the modules I am choosing to compile my kernel with...

Thanks

Alex

abrinister · 05-05-2011, 06:24 PM

Ok well I left alone the 2.38.4 kernel and got a fresh 2.38.5 source from the kernel site. I compiled it with tons of modules, and it all completed. It boots up fine until after the splash screen, when it tells me that there is no root device and that boot has failed forever. Why does this happen? Do I have to change the root directory in some file to make it work? This same problem happened to me when I built the rpm for an earlier kernel.

Thanks

Alex

abrinister · 05-06-2011, 03:49 PM

Ok I have found out the problem. Dracut is not finding a root partition because it is not initializing the volume group that the root partition is on. A quick and dirty fix to this is to add rdshell to your grub configuration file, then dracut will drop into a shell if it doesn't boot. From this shell, you need to enter:

Code:

lvm vgchange -ay

and then exit the shell by entering "exit". The kernel will then boot just fine. I do not think this is good fix, as you need to do this every time you boot. If anyone knows how to make this command run at boot by default, please share.

Thanks

Alex