Thanks. That third link especially helped. On Sat, Sep 18, 2010 at 5:47 PM, Tom H <tomh0665 at gmail.com> wrote: > On Sat, Sep 18, 2010 at 2:41 PM, Matthew Topper <topperm9 at gmail.com> wrote: >> On Sat, 18 Sep 2010 17:42:59 +0200 Timo Schoeler <timo.schoeler at riscworks.net> wrote: >> >>> On 09/18/2010 05:13 PM, Matthew Topper wrote: >>> > I'm playing with software RAID and LVM in some virtual machines and >>> > I've run into an issue that I can't find a good answer to in the >>> > docs. >>> > >>> > I have the following RAID setup: >>> > >>> > md0: sda1 and sdb1, RAID 1. This is /boot >>> > >>> > md1: sda2 and sdb2, RAID 1. This is a PV for LVM. >>> > >>> > VolGroup00, this is the volume group and md1 is the only PV in it. >>> > >>> > LogVol00 is swap >>> > LogVol01 is / >>> > LogVol02 is /home >>> > >>> > So, I tested to see what happens if I disable sdb in virtualbox. >>> > Machine booted find and I was able to see that part of the raid >>> > array was gone. >>> > >>> > I reattached the disk and rebuilt the array >>> > mdam --add /dev/md0 /dev/sdb1 >>> > mdam --add /dev/md1 /dev/sdb2 >>> > >>> > The array rebuilt without issue. But now, if I remove sda, the >>> > machine doesn't boot and grub complains. The question I have is >>> > how does one reinstall the boot sector at this point? I'm a little >>> > confused as far as to what device to install it on and what to >>> > specify as the root. >>> > >>> > This is grub.conf if it helps: >>> > >>> > default=0 >>> > timeout=5 >>> > splashimage=(hd0,0)/grub/splash.xpm.gz >>> > title CentOS (2.6.18-194.e15) >>> > root (hd0,0) >>> > kernel /vmlinuz-2.6.18-194.e15 ro >>> > root=/dev/VolGroup00/LogVol01 initrd /initrd-2.6.18-194.e15.img >>> > >>> > Grub has always been a little confusing for me, so I guess I don't >>> > understand. What do the two root entries specify? And again, my >>> > main question is how do I reinstall grub to the repaired disk? >>> >>> http://wiki.centos.org/HowTos/CentOS5ConvertToRAID#head-fa2b73a28acdf965daa1e018962eaa8cbd94110c >> >> Entering those commands exactly worked, but I'm not sure why it >> worked. So, it's progress. >> >> I need to find some good reference on GRUB, which seems difficult >> because most things I can find are about GRUB2, and CentOS has 0.97 > > The commands installed grub into the mbr of sdb that way you can boot > from either sda or sdb if the other is missing. > > You should always do that when booting from raid1 > http://wiki.centos.org/HowTos/SoftwareRAIDonCentOS5 > > GRUB1 manual > http://www.gnu.org/software/grub/manual/legacy/grub.html > > Good link (AFAIR) > http://members.iinet.net.au/~herman546/p15.html > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >