[SOLVED] how to install ArchLinux on a simple software raid 0

Question

I have two 256GB disks and I want them to be in raid 0.
I tried following this tutorial: https://wiki.archlinux.org/index.php/In … AID_or_LVM
but this tutorial has the added complication of LVM and raid 1 which I don't need.
I made 3 partitions on each of the disks:
sda1 - 100MB for /boot
sda2 - 2048MB for swap
sda3 - raid 0 md0
sdb1 - unused
sdb2 - 2048 for swap
sdb3 - raid 0 md0 for /
I can assemble and format the sda1(ext4), sda2(swap), sdb2(swap)  md0 (ext4) and install all the packages
I also configured mdadm.conf by Alt F2 at the installer and executing: mdadm --examine --scan > /mnt/etc/mdadm.conf
and added mdadm hook to the HOOKS list in /etc/mkinitcpio.conf (before 'filesystems')
configured the boot with grub outside of the installer as indicated in the tutorial
But when I boot I get:
md0: unknown partition table
Error: Unable to determine the file system of /dev/sda3
please help.
Last edited by 99Percent (2011-06-29 20:21:52)

Answer 1

fyi this is how I finally set up my simple 2 drive raid 0:
1. Create a bootable USB ArchLinux with UNetBootin
2. Boot with the USB
3. # /arch/setup
3. Select source: internet (highly recommended because i found out UNetBootin sources are not 100% reliable though not necessarily so, IOW just to be sure)
3. partition the two drives with 100mb for /boot and 100mb for swap (setup requires it - I have 8GB memory, I decided I don't need much swap space) and the rest of both sda and sdb which will make your raid 0.
4. ALT F2 to another terminal and create the the raid like this:
# modprobe raid0 (not sure if this is actually necessary)
# mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sda2 /dev/sdb2
5. go back to the setup screen with CTRL-ALT-F1
6. go to Prepare Hard Drives>Manually configure block devices, filesystems and mountpoints. Add the /boot (ext2) for sda1 swap for sdb1 and desired filesystem for md0 (I chose reiserfs). Ignore the rest of the devices.
7. Select packages. Add the base-devel just in case, but nothing else and install packages
8. ALT F2 again to the  terminal and run:
# mdamd --examine --scan > /mnt/etc/mdadm.conf
(this will configure the mdadm.conf to use your raid as created)
9. go back to the setup screen again with CTRL-ALT-F1
10. Select configure system
11. Edit /etc/rc.conf adding: raid0 to MODULES= like this:
MODULES=(raid0)
again not sure if necessary but it works for me
12. Edit /etc/mkinitcpio.conf adding dm_mod to the MODULES= like this:
MODULES="dm_mod"
13. also add to /etc/mkinitcpio.conf HOOKS= mdadm but before filesystems in my case it went like this:
HOOKS="base udev autodetect pata scsi sata mdadm filesystems"
14. I went ahead and uncommented a few mirrors in the mirrorlist file so I wouldn't have to deal with that later (and maybe it helps on the way).
15. Also set a root password. Not sure if it is even necessary but maybe some components require it.
16, Go to configure bootloader and select Grub
17. When asked "Do you have your system installed on software raid? answer Yes
18. When asked to edit the menu.lst file don't edit anything, just exit
19. When asked "Do you want to install grub to the MBR of each harddisk from your boot array? answer Yes
20. You will get "Error: Missing/Invalid root device:" and "GRUB was NOT successfully installed." Ignore those messages.
21. Exit the install
22. remove the USB stick and:
# reboot
23. the boot will fail and you will get a grub> prompt type the following commands:
grub> root (hd0,0)
grub> setup (hd0)
grub> reboot
Thats it!
Last edited by 99Percent (2011-06-28 18:51:59)