[clug] building bootable USB Flash drives - any good summary sites?

Rodney Peters rodneyp at iinet.net.au
Wed Oct 25 06:34:10 UTC 2017

On 25/10/17 13:50, steve jenkin via linux wrote:
> Yesterday I built a bootable USB stick because I wanted a Centos 6 environment.
> It didn’t help I hadn’t researched this topic well and tried to do this from Ubuntu using ‘unetbootin’.
> Got it working after a few false-starts and the odd bit of collateral damage (wiped SATA disk’s boot sector for grub, _twice_).
> Confirmed it worked on both a laptop and tower PC.
> Later found a Centos-specific site which said after 6.5 (latest is 6.9),
>   the instructions are "dd the iso image to the raw device, not a partition” - quick, simple and ‘worked as advertised’.
> The Centos ‘Live’ distro on the USB stick confuses ‘parted’, which says there’s a recursive MBR.
> ‘fdisk’ prints an MBR, as does ‘showpart’, which I think says “unrecognised boot loader”.
> using ‘xxd’, there is an x86 boot sector on the drive, didn’t know how to dig deeper than that.
> My lessons were:
>   - distros do things for USB installs a little differently, even in their own line. e.g. CentOS changed at 6.5.
>   - need to find specific instructions for the install you’re attempting to build a bootable system on a USB.
> Does anyone know of a good webpage / website that explains how the USB boot config & device setup/partitioning works,
> and might explain the differences between approaches?
> regards
> steve
> --
> Steve Jenkin, IT Systems and Design
> 0412 786 915 (+61 412 786 915)
> PO Box 38, Kippax ACT 2615, AUSTRALIA
> mailto:sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin

https://gparted.sourceforge.io/livehd.php    &

are peas from the same pod and explain fairly well how to put their 
dotIMG file on a USB stick.  They also explain the alternative for the 
dotISO file as well.  The latter is not suited to routine updates & 
configuration, but is OK for install medium or utility CD.

I've had first hand reports from several people that simply pointing 
your distro's installer to a blank USB device and doing the install 
produces a working solution.  You would need to identify all partitions 
via UUID so that GRUB can find them.

My interpretation is that if you want to put multiple dotIMG on the same 
stick then it might be feasible if each is installed to its own 
rootfilesystem partition, although they should be able to share a GRUB 
boot partition.

It is also possible to put multiple dotISO in the same /home/isos 
example and boot each but the kernel parameters are idiosyncratic and long.


has parameters for many distro covered.  Again, only well-suited to 
install medium or live CD

The change in procedures for Centos is probably because the dotISO was 
hybridised after 6.5.  Many now are - if not most can be hybridised by 
runing "isohybrid" against the dotISO file.  Still pot luck what type of 
device the BIOS will identify the USB stick as.  I have one PC which 
identifies it as "HHD" - not USB-HDD, USB-CDROM or USB-FDD.

openSUSE specifically warn against using "unetbootin"  - whatever the 
latter does now prevents the USB stick from booting correctly (might be 
related to UEFI boot ?)

have fun,


More information about the linux mailing list