Centos 7 i386 (altarch) install image does not boot from USB key drive

[mike978]

The Centos 7.2 1511 i386 seems to be a simple ISO image, suitable for a DVD image but not for a bootable usb key drive.

I used this procedure for writing to a USB key drive:

Code: Select all

# dd if=CentOS-7-i386-Everything-1511.iso of=/dev/sdX bs=1M

notes:

• sdX = sdb in my case
• I tried with bs=4M if that matters
• I tried, running dd on both a centos machine and a mac

the USB key drive is unbootable with "MISSING OPERATING SYSTEM". Centos 6.8 prepared in the same way boots fine.

Inserting the USB key into a working centos machine and checking dmesg, I noticed a message that the partition table was unknown.
It was mountable and readable as an iso image.

I suspect the ISO image was created the old way (before centos 6.5? or so) which wasn't also compatible with usb flash drives.

I'm a little unsure how to convert the ISO to a bootable .img format. The older instructions are unclear/may not apply.

My workaround? I bought a cheap usb dvd drive, burned the image to a DVD, and booted my machine from the usb dvd drive.

This worked.

I hope this helps someone.

Maybe someone could also fix the image to be bootable from a usb key drive, or document the limitation.