Craig White wrote:
On Tue, 2006-03-28 at 08:05 -0700, Craig White wrote:
> On Mon, 2006-03-27 at 21:43 -0600, Laurence Vanek wrote:
>
>> Greetings -
>>
>> To my surprise, fresh install of FC5 with RAID 1 configured at install
>> time went without a hitch. I have /dev/md0 defined on /boot
>> partitions. It boots fine with this setup.
>>
>> I had my FC4 system setup this exact way except I found that I had to
>> manually install grub on one of the disks to permit booting off either
>> one if the other is down.
>>
>> Does anyone know of a way to check for the presence of grub on each
>> drive (obviously its on hda since it boots presently) to see if this
>> needs to be done for FC5 also without powering down each drive in turn &
>> attempting to boot?
>>
> ----
> thought I should post against the right thread
>
> just an untested thought...
>
> bb if=/dev/sda of=/tmp/sda-bootblock.bin bs=512 count=1
> bb if=/dev/sdb of=/tmp/sdb-bootblock.bin bs=512 count=1
>
> diff /tmp/sda-bootblock.bin /tmp/sdb-bootblock.bin
>
> Thinking...
>
> - substitute different values for sda/sdb as fits
> - the first 512 bytes on each drive are the boot (perhaps less, someone
> will surely correct me...it might just be the first 256 or 384 bytes)
> - if they are the same (i.e. grub has been installed on both), there
> will be no diff
>
> otherwise...
>
> grub-install /dev/sdb
>
> Of course, the only way that you'll ever KNOW for sure that it's going
> to work is to do a real simulation, i.e. disconnecting one drive, then
> the other drive...
>
----
not only wrong thread but as Paul so correctly points out.
dd - NOT bb
I am rapidly ingesting coffee but haven't figured out a mainline method
so I am left to normal ingestion methods which apparently haven't quite
caught up to my fingers or my brain.
duh.
Sorry
Craig
Craig -
results using bs=466
============
[root@localhost tmp]# dd if=/dev/hda of=/tmp/hda-bootblock.bin bs=466
count=1
1+0 records in
1+0 records out
466 bytes (466 B) copied, 7.6e-05 seconds, 6.1 MB/s
[root@localhost tmp]# dd if=/dev/hdc of=/tmp/hdc-bootblock.bin bs=466
count=1
1+0 records in
1+0 records out
466 bytes (466 B) copied, 7.7e-05 seconds, 6.1 MB/s
[root@localhost tmp]# diff hda-bootblock.bin hdc-bootblock.bin
Binary files hda-bootblock.bin and hdc-bootblock.bin differ
================
files also differ is bs=256, 128
BUT for bs=64 we get no complaint from diff:
================
[root@localhost tmp]# dd if=/dev/hda of=/tmp/hda-bootblock.bin bs=64 count=1
1+0 records in
1+0 records out
64 bytes (64 B) copied, 7.8e-05 seconds, 821 kB/s
[root@localhost tmp]# dd if=/dev/hdc of=/tmp/hdc-bootblock.bin bs=64 count=1
1+0 records in
1+0 records out
64 bytes (64 B) copied, 7.6e-05 seconds, 842 kB/s
[root@localhost tmp]# diff hda-bootblock.bin hdc-bootblock.bin
================