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Old 01-17-2014, 08:18 AM   #1
LQ Newbie
Registered: Oct 2004
Location: Dorset, UK
Distribution: Slackware 14.1
Posts: 17

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Grub2, Dual boot and RAID problems

Hi folks,

I have a long-running problem with getting a dual boot system working.

I have four SATA 1Tb hard drives, all plugged directly into the mobo where the BIOS is set to emulate IDE. They are each split into four partitions. 1st 10 Gb for /, 2nd 10 Gb for swap, 3rd 960Gb for /home & 4th 20 Gb for /opt .
The first three are given over totally to raid5 using md, thus sd[abc]1 make up md1, sd[abc]2 make md2, sd[abc]3 make md3 & sd[abc]4 make md4. They are all labelled, raid_root, raid_swap, raid_home & raid_opt respectively. Debian Wheezy 64 is installed on this RAID5 set with the partitions mounted as described by the labels. Grub2 is the bootloader and is installed to the MBR of the first drive. This system boots and runs okay.

The fourth hard drive is identically partitioned with the labelling s_root, s_swap, s_home & s_opt. I would have liked to use drive this as part of the main systems raid but as Wheezy is pretty rubbish for gaming I have kept this drive for a Vector 6.0 (based on Slackware 12) installation. I would like to be able to dual boot this using the grub2 from the main system.

However, I ran into problems trying to install any system onto this fourth drive, I did try several distros with varying results but little luck. Eventually I unplugged the first three drives and installed Vector 6.0 with no trouble at all. This used LILO, the conf file is shown below.
boot = /dev/sda
timeout = 50
# lba32
vga = 791

# Vector_GUI
image = /boot/vmlinuz
initrd= /boot/initrd
label = Vector_GUI
root = /dev/disk/by-label/s_root
append="4 "

# Vector Text
image = /boot/vmlinuz
initrd = /boot/initrd
label = Vector_TUI
root = /dev/disk/by-label/s_root
append = "2 nosplash"

You will note that nowhere have I referred to any partition except by use of the label. The only use of a device name is in the 'boot=' where I could see no alternative & believe that this is only used by lilo during installation & should have no effect thereafter, is this correct? As this stood, with the first three drives unplugged, the system behaves beautifully.

I then plugged the other drives back in and, on booting into Debian, added the new system to GRUB. Initially I tried letting GRUB work it out using os-prober which created
menuentry "Slackware Linux (Slackware 12.1.0) (on /dev/sdh1)" --class gnu-linux --class gnu --class os {
insmod part_msdos
insmod ext2
set root='(/dev/sdh,msdos1)'
linux /boot/vmlinuz root=/dev/sdh1
initrd /boot/initrd

but this resulted in GRUB throwing up 'error: no such disc' when executing the 'linux /boot/....' line. Using the GRUB editor I have tried all sda[a..z] drive options, all give the same error.

So I added Vector manually to GRUBs 40_custom file. I have tried several variations over the past weeks but it currently stands as shown below. This appears to perform correctly but I cannot be sure.
menuentry "Vector_GUI (on 4th HD)" --class gnu-linux --class gnu --class os {
insmod part_msdos
insmod ext2
# set root='(hd3,msdos1)' /*Now covered by 'search line'.*/
search --label --set root s_root
echo "Loading Vector vmlinuz ......."
linux /boot/vmlinuz root=/dev/disk/by-label/s_root ro vga=793 quiet nomodeset
echo "Loading Vector initrd ....."
initrd /boot/initrd

I'm not too hot on GRUB, does this appear correct?

On booting GRUB appears to pass control to the Vector boot process correctly, however I cannot confirm this. Immediately after the linux kernel (or initrd) starts it reports
pci 0000.00.00.0 bar 3: can't allocate resources
ata1: softreset failed (device not ready)
ata2: softreset failed (device not ready)
ata3: softreset failed (device not ready)
ata4: softreset failed (device not ready)
md: invalid raid superblock magic on sda1
md: invalid raid superblock magic on sda2
md: invalid raid superblock magic on sda3
md: invalid raid superblock magic on sda4
md: invalid raid superblock magic on sdb1
md: invalid raid superblock magic on sdb2
md: invalid raid superblock magic on sdb3
md: invalid raid superblock magic on sdb4
md: invalid raid superblock magic on sdc1
md: invalid raid superblock magic on sdc2
md: invalid raid superblock magic on sdc3
md: invalid raid superblock magic on sdd4
kernel panic not syncing VFS: Unable to mount root fs on unknown block (0,0)

Why is it trying to access the RAID? I would like to use the same home partition later but at this point these drives are totally irrelevant to Vector. Vector uses while Wheezy uses 3.2.0-4-amd64. Possibly, the softreset errors indicate that a version 3 kernel may be running as this is something I often see post 3.0 but not with older versions? Is there a way to check which kernel and partition are active here?

With all four drives in, and telling the BIOS to boot from the fourth drive, Vector get much further before again 'panic'ing with 'kernel panic not syncing VFS: Unable to mount root fs on unknown block (8,0)'. The text scrolls far too fast to see how far the boot gets but it appears to be trying to use an invalid partition for /. Immediately prior to the panic it lists all partitions just after appearing to try and identify the fs type on sda1. I have looked into /var/log/ on s_root but there is no record of the failed boots.

My fstab for Vector is:-
LABEL=s_root / ext2 defaults 1 1
LABEL=s_swap none swap sw 0 0
LABEL=s_home /home ext3 defaults 1 2
LABEL=s_opt /opt ext3 defaults 1 2
devpts /dev/pts devpts gid=5,mode=620 0 0
proc /proc proc defaults 0 0

This works perfectly when this is the only drive installed. In this situation the system identifies the drive as sda while Debian, with a four drive setup identifies it as sdh. However, I believe have used labels throughout. In order to check this I have 'cd'ed into Vector /etc and run 'grep -r sda1 ./*', the only instances of this string are in commented out & replaced lines.

So, at the moment the only way I can use any 32bit software with a heavy graphics demand (specifically X3: Reunion) is to dismantle the case and unplug the first three drives, very much a highly undesirable solution. Can anyone help?
Old 01-19-2014, 06:00 PM   #2
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Registered: Aug 2009
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Apologies in advance, but this is not really a helpful response .. I'm a big fan of keeping it simple and to that end, I believe you're better off using virtualisation rather than multi-boot - these days the graphics performance is pretty good under Spice/KVM if that's what is driving you. I also avoid software raid due to the added complexity, raid controllers are not expensive and IMO perform better due to doing it in dedicated silicon and not in the OS/CPU.

I'm not trying to rain on your parade, just saying that there are better things to spend your time on

1 members found this post helpful.
Old 01-20-2014, 11:08 PM   #3
LQ Newbie
Registered: Oct 2004
Location: Dorset, UK
Distribution: Slackware 14.1
Posts: 17

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Hi kbp,
I have been using VirtualBox but find it's abilty to use my graphics card memory too limiting. My nvidia GT630 has 2Gb RAM on board but the VM will only use 256Mb of it - certainly inadequate for playing X3.

I did use an Adaptec 3410 card for a time but swapped it out for software RAID for two reasons:-
(a) My computer has overheating problems, I have five fans running in the case but the system still overheats at times. A RAID card runs extremely hot, the temperature problem significantly improved when it was removed.
(b) The RAID card had a maximum throughput of 3GB/s per drive, this is hard to improve on without spending a lot of money and a faster card will be putting out even more heat. So the hardware RAID could run my RAID at 6GB/s max. My four hard drives (new Seagate Barracudas) do 6Gb/s each, so md will theoretically do 12GB/s though overheads mean this can never be actually achieved. However, the software RAID system does run very noticeably faster than it ever did on hardware. With a quad-core processor md's software load is insignicant.

Thanks for your reply. Maybe I should give up the games playing and get down to work. Though having a system many MS-Windows gamers would die for (quad-core Phenom, 12Gb RAM, GT630 video with 2GB RAM & a fast hard drive system) it seems a shame not to use it. It's certainly nice too see my brother in awe at how much better my Linux system runs X3 than his MS-Windows system does.
Old 01-26-2014, 06:33 PM   #4
LQ Newbie
Registered: Oct 2004
Location: Dorset, UK
Distribution: Slackware 14.1
Posts: 17

Original Poster
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Hi again,
Thanks kbp, going simple was the way. I found one distro that gives me all I need i.e Slackware 14.1. It immediately picked up my raid setup, gave no quibbling about installing nvidias proprietary driver and easily allowed me to add Vectors' GUI admin tools. Also, the installation, using LILO, had no problem detecting & setting up my Debian.

I had forgotten what a lovely, and very underrated, distro Slackware is. How, by leaving out the bling, everything just works.

I will run it like this for a few weeks soaking & then dump Debian to give me a single boot setup.
Old 01-27-2014, 04:52 PM   #5
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Glad to hear it's all working


dual boot, grub2, md, vector, vectorlinux

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