[CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[m.roth at 5-cent.us]

Emmanuel Noobadmin wrote:
> On a random hunch or sheer desperation, I inserted an old brandless
> 1GB USB thumbdrive, installed and it booted.
>
> Thinking that the Sandisk Ultra Backup 16GB was incompatible with
> CentOS/grub for some unknown reason. I switched to a brandless 16GB,
> installed the same way and it failed at grub prompt again.
>
> Now it is starting to look as if either the newer drives have
> something on them that prevents booting. Or it's the total size of the
> drive, regardless of the partition size. I say this because in every
> case I used a single 1GB ext4 / partition for testing, to reduce the
> mkfs time.
>
<snip>
>
> It seems that the common issue is starting at sector 2048 so I fdisk
> the 16GB Sandisk to manually create a 1GB partition started at sector
> 63. Using this, I installed and was able to boot successfully.
>
> To verify, I use the same 16GB disk to install again, deleting the
> partition in anaconda and creating a new 1GB partition, ctrl-alt-f2
> and fdisk confirms it was again at sector 2048.
>
> As a side note, for some reason, drive geometry changed for the 16GB
> after a reinsert to varying values such as
> 6 heads, 33 sectors/track, 159164 cylinders
> 16 heads, 32 sectors/track, 61551 cylinders
>
> Not sure if this had any significance to why anaconda decides to fdisk
> the drive starting from sector 2048.

Wonder if it's trying to beat the rush - after weeks of googling, a few
weeks ago, I finally found that if I formatted my 3TB drives on a 4k
boundry, instead of a 512byte boundry, writes were literally about four
times faster, because that's the physical sector on the drives.

It may be trying to do the same, to take care of this invisibly.

Good catch on the USB drive business.

        mark